% % This file was created by the Typo3 extension % sevenpack version 0.7.16 % % --- Timezone: CEST % Creation date: 2021-10-23 % Creation time: 04-24-04 % --- Number of references % 555 % @Article { Noack2021, title = {On closures for reduced order models -- A spectrumof first-principle to machine-learned avenues}, journal = {Physics of Fluids}, year = {2021}, month = {9}, day = {1}, volume = {33}, number = {5}, pages = {33}, abstract = {For over a century, reduced order models (ROMs) have been a fundamental discipline of theoretical fluid mechanics. Early examples include Galerkin models inspired by the Orr-Sommerfeld stability equation and numerous vortex models, of which the von Karman vortex street is one of the most prominent. Subsequent ROMs typically relied on first principles, like mathematical Galerkin models, weakly nonlinear stability theory, and two- and three-dimensional vortex models. Aubry et al. [J. Fluid Mech. 192, 115-173 (1988)] pioneered the data-driven proper orthogonal decomposition (POD) modeling. In early POD modeling, available data were used to build an optimal basis, which was then utilized in a classical Galerkin procedure to construct the ROM, but data have made a profound impact on ROMs beyond the Galerkin expansion. In this paper, we take a modest step and illustrate the impact of data-driven modeling on one significant ROM area. Specifically, we focus on ROM closures, which are correction terms that are added to the classical ROMs in order to model the effect of the discarded ROM modes in under-resolved simulations. Through simple examples, we illustrate the main modeling principles used to construct the classical ROMs, motivate and introduce modern ROM closures, and show how data-driven modeling, artificial intelligence, and machine learning have changed the standard ROM methodology over the last two decades. Finally, we outline our vision on how the state-of-the-art data-driven modeling can continue to reshape the field of reduced order modeling.}, url = {https://doi.org/10.1063/5.0061577}, howpublished = {online}, DOI = {10.1063/5.0061577}, author = {Ahmed, S. and Pawar, S. and San, O. and Rasheed, A. and Iliescu, T. and Noack, B. R.} } @Article { Perez-Becker2021, title = {Implementation and validation of an advanced wind energy controller in aero-servo-elastic simulations using the lifting line free vortex wake model}, journal = {Energies}, year = {2021}, volume = {14}, number = {3}, abstract = {Accurate and reproducible aeroelastic load calculations are indispensable for designing modern multi-MW wind turbines. They are also essential for assessing the load reduction capabilities of advanced wind turbine control strategies. In this paper, we contribute to this topic by introducing the TUB Controller, an advanced open-source wind turbine controller capable of performing full load calculations. It is compatible with the aeroelastic software QBlade, which features a lifting line free vortex wake aerodynamic model. The paper describes in detail the controller and includes a validation study against an established open-source controller from the literature. Both controllers show comparable performance with our chosen metrics. Furthermore, we analyze the advanced load reduction capabilities of the individual pitch control strategy included in the TUB Controller. Turbulent wind simulations with the DTU 10 MW Reference Wind Turbine featuring the individual pitch control strategy show a decrease in the out-of-plane and torsional blade root bending moment fatigue loads of 14\% and 9.4\% respectively compared to a baseline controller.}, keywords = {wind energy; wind turbine control; load mitigation; individual pitch control; lifting line free vortex wake; vortex methods}, url = {https://www.mdpi.com/1996-1073/14/3/783}, author = {Perez-Becker, S. and Marten, D. and Nayeri, C. N. and Paschereit, C. O.} } @Article { Klukas.2020, title = {Anchoring of turbulent premixed hydrogen/air flames at externally heated walls}, journal = {International Journal of Hydrogen Energy}, year = {2020}, month = {10}, day = {10}, volume = {45}, number = {56}, pages = {32547--32561}, abstract = {A joint experimental and numerical investigation of turbulent flame anchoring at externally heated walls is presented. The phenomenon has primarily been studied for laminar flames and micro-combustion while this study focuses on large-scale applications and elevated Reynolds number flows. Therefore, a novel burner design is developed and examined for a diverse set of operating conditions. Hydroxyl radical chemiluminescence measurements are employed to validate the numerical method. The numerical investigation evaluates the performance of various hydrogen/air kinetics, Reynolds-averaged turbulence models and the eddy dissipation concept (EDC) as a turbulence-chemistry interaction model. Simulation results show minor differences between detailed chemical mechanisms but pronounced deviations for a reduced kinetic. The baseline k-\(\omega\) turbulence model is assessed to most accurately predict flame front position and shape. Universal applicability of EDC modeling constants is contradicted. Conclusively, the flame anchoring concept is considered a promising approach for pilot flames in continuous combustion devices.}, keywords = {Eddy dissipation concept;Hydrogen/air chemical kinetics;Steady flame anchoring;Wall heat transfer}, ISSN = {03603199}, DOI = {10.1016/j.ijhydene.2020.08.201}, author = {Klukas, S. and Giglmaier, M. and Adams, N.A. and Sieber, M. and Schimek, S. and Paschereit, C. O.} } @Article { Bluemner2020cnf}, title = {Effect of inlet and outlet boundary conditions on rotating detonation combustion}, journal = {Combustion and Flame}, year = {2020}, month = {6}, volume = {216}, pages = {300-315}, abstract = {In this work, the effect of different injector geometries and different outlet restrictions on the operating modes of a hydrogen-air Rotating Detonation Combustor (RDC) is investigated. The different operating modes are identified based on pressure measurements in the combustor annulus and the reactant supply, combined with high-speed video from the aft end of the combustor. The pressure frequency spectra are analyzed to determine the global operating mode in terms of number, direction, and speed of waves. The results explore the ability of the RDC to establish rotating, counter-rotating, and longitudinal waves, as well as their superpositions. A good agreement between longitudinal modes and the acoustic resonance frequencies of the RDC annulus was found. Overall, operation was found to be highly injector and outlet restriction dependent. Adding an outlet restriction helped to suppress counter-rotating waves, which is a prerequisite to stabilize single detonation waves. However, it was also shown to prompt high frequency pulsed operation. Apart from the total reactant supply pressure, the relative strength of the injectors was identified as a key factor for stable RDC operation. Pressure feedback into the reactant supply was observed to be dependent on the reactant supply pressure and the RDC operating mode. The study further revealed the presence of transverse resonance modes in the fuel plenum, however these oscillations were weak relative to the injector pressures and do not appear to influence the combustion.}, url = {https://doi.org/10.1016/j.combustflame.2020.03.011}, ISSN = {0010-2180}, DOI = {10.1016/j.combustflame.2020.03.011}, author = {Bl{\"u}mner, R. and Bohon, M. and Paschereit, C. O. and Gutmark, E.} } @Article { Wieser_2020, title = {Wake structures and surface patterns of the DrivAer notchback car model under side wind conditions}, journal = {energies}, year = {2020}, month = {1}, day = {9}, volume = {13}, pages = {18}, abstract = {The flow field topology of passenger cars considerably changes under side wind conditions. This changes the surface pressure, aerodynamic force, and drag and performance of a vehicle. In this study, the flow field of a generic passenger vehicle is investigated based on three different side wind angles. The study aimed to identify vortical structures causing changes in the rear pressure distribution. The notchback section of the DrivAer model is evaluated on a scale of 1:4. The wind tunnel tests are conducted in a closed section with a splitter plate at a Reynolds number of 3 million. The side wind angles are 0\(^{\circ}\) , 5\(^{\circ}\), and 10\(^{\circ}\). The three-dimensional and time-averaged flow field downstream direction of the model is captured by a stereoscopic particle image velocimetry system performed at several measurement planes. These flow field data are complemented by surface flow visualizations performed on the entire model. The combined approaches provide a comprehensive insight into the flow field at the frontal and side wind inflows. The flow without side wind is almost symmetrical. Longitudinal vortices are evident along the downstream direction of the A-pillar, the C-pillars, the middle part of the rear window, and the base surface. In addition, there is a ring vortex downstream of the vehicle base. The side wind completely changes the flow field. The asymmetric topology is dominated by the windward C-pillar vortex, the leeward A-pillar vortex, and other base vortices. Based on the location of the vortices and the pressure distributions measured in earlier studies, it can be concluded that the vortices identified in the wake are responsible for the local minima of pressure, increasing the vehicle drag.}, keywords = {DrivAer; aerodynamics; wind tunnel; vehicle; flow visualization; PIV; wake structures; side wind; crosswind}, url = {https://www.mdpi.com/1996-1073/13/2/320/htm}, DOI = {doi.org/10.3390/en13020320}, author = {Wieser, D. and Nayeri, C. N. and Paschereit, C. O.} } @Article { Saverin2020, title = {Advances toward a lightweight, variable fidelity wake simulation tool}, journal = {Journal of Physics: Conference Series}, year = {2020}, volume = {1618}, pages = {052070}, abstract = {A method is presented which aims to bridge the gap between overly simplified momentum-based wake models and overly demanding finite volume models of wind turbine wake evolution. The method has been developed to allow an essentially user-defined resolution of the wake. Beyond this, all dominant field quantities are automatically resolved by the solver including convection velocity, shear stress and turbulence intensity. Two distinct methods of solution are presented which both have strengths and weaknesses, the choice of which model being fidelity and application dependent. Both methods make use of multilevel spatial integration to allow greatly improved computational efficiency. The method is here presented for 2D flow in the symmetry plane of a vertical axis wind turbine as an initial demonstration of the potential of the method.}, url = {https://doi.org/10.1088/1742-6596/1618/5/052070}, DOI = {10.1088/1742-6596/1618/5/052070}, author = {Saverin, J. and Marten, D. and Nayeri, N. and Paschereit, C. O.} } @Article { Alber2020, title = {Aerodynamic effects of Gurney Flaps on the rotor blades of a research wind turbine}, journal = {Wind Energy Science}, year = {2020}, volume = {5}, number = {4}, pages = {1645--1662}, url = {https://wes.copernicus.org/articles/5/1645/2020/}, DOI = {10.5194/wes-5-1645-2020}, author = {Alber, J. and Soto-Valle, R. and Manolesos, M. and Bartholomay, S. and Nayeri, C. N. and Sch{\"o}nlau, M. and Menzel, C. and Paschereit, C. O. and Twele, J. and Fortmann, J.} } @Article { Asli2020, title = {Aerodynamic investigation of guide vane configurations downstream a rotating detonation combustor}, journal = {Journal of Engineering for Gas Turbines Power}, year = {2020}, pages = {24}, abstract = {Any outlet restriction downstream of Pressure Gain Combustion (PGC), such as turbine blades, affects its flow field and may cause additional thermodynamic losses. The unsteadiness in the form of pressure, temperature and velocity vector fluctuations has a negative impact on the operation of conventional turbines. Additionally, experimental measurements and data acquisition present researchers with challenges that have to do mostly with the high temperature exhaust of PGC and the high frequency of its operation. Nevertheless, numerical simulations can provide important insights into PGC exhaust flow and its interaction with turbine blades. In this paper, a Rotating Detonation Combustor (RDC) and a row of nozzle guide vanes have been modeled based on the data from literature and an available experimental setup. URANS simulations were done for five guide vane configurations with different geometrical parameters to investigate the effect of solidity and blade type representing different outlet restrictions on the RDC exhaust flow. The results analyzed the connection between total pressure loss and the vanes solidity and thickness to chord ratio. It is observed that more than 57 \% of the upstream velocity angle fluctuation amplitude was damped by the vanes. Furthermore, the area reduction was found to be the significant driving factor for damping the velocity angle fluctuations, whether in the form of solidity or thickness on chord ratio increment. This RDC exhaust flow investigation is an important primary step from a turbomachinery standpoint, which provided details of blade behavior in such an unsteady flow field.}, note = {GTP-20-1512}, keywords = {Combustion chambers, explosions, guide vanes, exhaust systems, flow (Dynamics), pressure, blades, chords (Trusses), fluctuations (Physics), turbine blades, combustion, computer simulation, damping, data acquisition, engineering simulation, high temperature, nozzle guide vanes, simulation, temperature, turbines, turbomachinery, unsteady flow}, url = {https://elib.dlr.de/139560/1/Manuskript.pdf}, DOI = {https://doi.org/10.1115/1.4049188}, author = {Asli, M. and Stathopoulos, P. and Paschereit, C. O.} } @Article { Bach2019symp}, title = {An empirical model for stagnation pressure gain in rotating detonation combustors (in press)}, journal = {Proceedings of the Combustion Institute}, year = {2020}, DOI = {10.1016/j.proci.2020.07.071}, author = {Bach, E. and Paschereit, C. O. and Stathopoulos, P. and Bohon, M.} } @Article { yuecel2019symp}, title = {Autoignition in stratified mixtures for pressure gain combustion (in press)}, journal = {Proceedings of the Combustion Institute}, year = {2020}, DOI = {10.1016/j.proci.2020.07.108}, author = {Y{\"u}cel, F. and Habicht, F. and Bohon, M. and Paschereit, C. O.} } @Article { Perez-Becker2020, title = {Blade element momentum theory overestimating wind turbine loads? - An aeroelastic comparison between OpenFAST's AeroDyn and QBlade's Lifting-Line Free Vortex Wake method''}, journal = {Wind Energy Science, vol. 5, pp. 721-743,(2020)}, year = {2020}, volume = {5}, number = {5}, pages = {721-743}, abstract = {Load calculations play a key role in determining the design loads of different wind turbine components. To obtain the aerodynamic loads for these calculations, the industry relies heavily on the Blade Element Momentum (BEM) theory. BEM methods use several engineering correction models to capture the aerodynamic phenomena present in Design Load Cases (DLCs) with turbulent wind. Because of this, BEM methods can overestimate aerodynamic loads under challenging conditions when compared to higher-order aerodynamic methods - such as the Lifting-Line Free Vortex Wake (LLFVW) method - leading to unnecessarily high design loads and component costs. In this paper, we give a quantitative answer to the question of load overestimation of a particular BEM implementation by comparing the results of aeroelastic load calculations done with the BEMbased OpenFAST code and the QBlade code, which uses a particular implementation of the LLFVW method. We compare extreme and fatigue load predictions from both codes using sixty-six 10 min load simulations of the Danish Technical University (DTU) 10MW Reference Wind Turbine according to the IEC 61400-1 power production DLC group. Results from both codes show differences in fatigue and extreme load estimations for the considered sensors of the turbine. LLFVW simulations predict 9\% lower lifetime damage equivalent loads (DELs) for the out-ofplane blade root and the tower base fore-aft bending moments compared to BEM simulations. The results also show that lifetime DELs for the yaw-bearing tilt and yaw moments are 3\% and 4\% lower when calculated with the LLFVW code. An ultimate state analysis shows that extreme loads of the blade root out-of-plane bending moment predicted by the LLFVW simulations are 3\% lower than the moments predicted by BEM simulations. For the maximum tower base fore-aft bending moment, the LLFVW simulations predict an increase of 2 \%. Further analysis reveals that there are two main contributors to these load differences. The first is the different way both codes treat the effect of the nonuniform wind field on the local blade aerodynamics. The second is the higher average aerodynamic torque in the LLFVW simulations. It influences the transition between operating modes of the controller and changes the aeroelastic behavior of the turbine, thus affecting the loads.}, url = {https://doi.org/10.5194/wes-5-721-2020}, DOI = {10.5194/wes-5-721-2020}, author = {Perez-Becker, S. and Papi, F. and Saverin, J. and Marten, D. and Biancini, A. and Paschereit, C. O.} } @Article { Noack_29062020, title = {Cartographing dynamic stall with machine learning}, journal = {Wind Energy Science}, year = {2020}, volume = {5}, number = {2}, pages = {819-838}, abstract = {Once stall has set in, lift collapses, drag increases and then both of these forces will fluctuate strongly. The result is higher fatigue loads and lower energy yield. In dynamic stall, separation first develops from the trailing edge up the leading edge. Eventually the shear layer rolls up, and then a coherent vortex forms and then sheds downstream with its low-pressure core causing a lift overshoot and moment drop. When 50+ experimental cycles of lift or pressure values are averaged, this process appears clear and coherent in flow visualizations. Unfortunately, stall is not one clean process but a broad collection of processes. This means that the analysis of separated flows should be able to detect outliers and analyze cycle-to-cycle variations. Modern data science and machine learning can be used to treat separated flows. In this study, a clustering method based on dynamic time warping is used to find different shedding behaviors. This method captures the fact that secondary and tertiary vorticity vary strongly, and in static stall with surging flow the flow can occasionally reattach. A convolutional neural network was used to extract dynamic stall vorticity convection speeds and phases from pressure data. Finally, bootstrapping was used to provide best practices regarding the number of experimental repetitions required to ensure experimental convergence.}, url = {https://wes.copernicus.org/articles/5/819/2020/}, DOI = {https://doi.org/10.5194/wes-5-819-2020}, author = {Lennie, M. and Steenbuck, J. and Noack, B. R. and Paschereit, C. O.} } @Article { Balduzzi2020, title = {Combined numerical and experimental study on the use of Gurney Flaps for the performance enhancement of NACA0021 airfoil in static and dynamic conditions}, journal = {ASME Digital Collection}, year = {2020}, abstract = {Power augmentation devices in wind energy applications have been receiving increasing interest from both the scientific and the industrial community. In particular, Gurney Flaps (GFs) showed a great potential thanks to the passive functioning, the simple construction and the possibility to add them as a retrofit to existing rotors. Within this context, the authors have performed an extended investigation on the lift increase capabilities of GFs for the well-known NACA 0021 airfoil, which has been used in several wind energy applications up to now. The present paper shows the results of a combined experimental and numerical analysis considering different geometrical configurations of the flaps under both static and dynamic conditions. Experimental data were first obtained for the AoA range of 180 degrees at a Reynolds number of 180 k to analyze the impact of three different geometrical configurations of the GF on the aerodynamic behavior. The geometrical configurations were defined by varying the length of the flap (1.4 \% and 2.5 \% of the chord) and its inclination angle with respect to the blade chord (90 degrees and 45 degrees). The experimental investigation involved also dynamic sinusoidal pitching movements at multiple reduced frequencies to evaluate the stall hysteresis cycle. An unsteady CFD numerical model was calibrated against wind tunnel data and then exploited to extend the investigation to a wider range of Reynolds numbers for dynamic AoA rates of change typical of vertical-axis wind turbines, i.e. characterized by higher reduced frequencies with a non-sinusoidal motion law.}, url = {https://doi.org/10.1115/1.4048908}, author = {Balduzzi, F. and Holst, D. and Melani, P. F. and Wegner, F. and Nayeri, C. N. and Ferrara, G. and Paschereit, C. O. and Bianchini, A.} } @Article { Soto-Valle_2020, title = {Determination of the angle of attack on a research wind turbine rotor blade using surface pressure measurements}, journal = {Wind Energy Science Discussions}, year = {2020}, pages = {1-28}, abstract = {In this paper, a method to determine the angle of attack on a wind turbine rotor blade using a chordwise pressure distribution measurement was applied. The approach uses a reduced number of pressure taps data located close to the blade leading edge. The results were compared with three 3-hole probes located at different radial positions and analytical calculations. The experimental approaches are based on the 2-D flow assumption; the pressure tap method is an application of the thin airfoil theory and the 3-hole probe method uses external probe measurements and applies geometrical and induction corrections.The experiments were conducted in the wind tunnel at the Hermann F{\"o}ttinger Institut of the Technische Unversit{\"a}t Berlin. The research turbine is a three-bladed upwind horizontal axis wind turbine model with a rotor diameter of 3 m. The measurements were carried out at rated condition with a tip speed ratio of 4.35 and different yaw and pitch angles were tested in order to compare both methods over a wide range of conditions.Results show that the pressure taps method is suitable with a similar angle of attack results as the 3-hole probes for the aligned case. When a yaw misalignment was introduced the method captures the same trend and feature of the analytical estimations. Nevertheless, it is not able to capture the tower influence. Regarding the influence of pitching the blades, a linear relationship between the angle of attack and pitch angle was found.}, url = {https://wes.copernicus.org/preprints/wes-2020-35/}, DOI = {10.5194/wes-2020-35}, author = {Soto-Valle, R. and Bartholomay, S. and Alber, J. and Manolesos, M. and Nayeri, C. N. and Paschereit, C. O.} } @Article { Bohon2019shock}, title = {Dynamic mode decomposition analysis of rotating detonation waves}, journal = {Shock Waves}, year = {2020}, DOI = {doi.org/10.1007/s00193-020-00975-8}, author = {Bohon, M. and Orchini, A. and Bl{\"u}mner, R. and Paschereit, C. O. and Gutmark, E.} } @Article { Müller-Vahl2020, title = {Dynamic stall under combined pitching and surging}, journal = {AIAA Journal}, year = {2020}, volume = {58}, number = {12}, pages = {5134-5145}, url = {https://arc.aiaa.org/doi/pdf/10.2514/1.J059153}, DOI = {10.2514/1.j059153}, author = {M{\"u}ller-Vahl, H. F. and Strangfeld, C. and Nayeri, C. N. and Paschereit, C. O. and Greenblatt, D.} } @Article { RezayHaghdoost2020a, title = {High-speed Schlieren and particle image velocimetry of the exhaust flow of a pulse detonation combustor}, journal = {AIAA Journal}, year = {2020}, volume = {58}, number = {8}, pages = {3527--3543}, url = {https://arc.aiaa.org/doi/abs/10.2514/1.J058540 https://arc.aiaa.org/doi/10.2514/1.J058540}, ISSN = {0001-1452}, DOI = {10.2514/1.J058540}, author = {Rezay Haghdoost, M. and Edgington-Mitchell, D. and Paschereit, C. O. and Oberleithner, K.} } @Article { Lückoff2020, title = {Impact of the precessing vortex core on NOx emissions in premixed swirl-Stabilized flames - an experimental study}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2020}, volume = {142}, number = {11}, url = {https://doi.org/10.1115/1.4048603 https://asmedigitalcollection.asme.org/gasturbinespower/article/doi/10.1115/1.4048603/1087526/Impact-of-the-Precessing-Vortex-Core-on-NOx}, publisher = {\{\{\}ASME\{\}\} International}, ISSN = {0742-4795}, DOI = {10.1115/1.4048603}, author = {L{\"u}ckoff, F. and Sieber, M. and Paschereit, C. O. and Oberleithner, K.} } @Article { Asli_2020, title = {Investigation of stationary vanes aerodynamic performance under different RDC exhaust}, journal = {22nd Australasian Fluid Mechanics Conference AFMC2020 Brisbane, Australia, 7 - 10 December 2020}, year = {2020}, abstract = {High level of unsteadiness existing in a high-temperature Rotating Detonation Combustor exhaust flow is extremely deteriorative for conventional turbomachinery that spoils the efficiency gained by constant volume combustion. In the present paper, it is tried to study the presence of a simple row of turbine guide vane downstream of an RDC. Unsteady numerical investigation is done on an experimental RDC model simulating three different operating modes all of which provide a single rotating detonation wave. Fluctuation frequency and amplitude are tracked to investigate the flow behavior in detail and the results are compared with the experimental measurements. Furthermore, total pressure loss is measured along the vanes. It is concluded that increasing RDC mass flow rate would lead to increase fluctuation frequency that also causes higher total pressure loss through the blade row. Additionally, three different flow regimes were observed for the different operating modes, which should be considered by turbine designers.}, keywords = {Turbine guide vane; unsteady flow; rotating detonation; aerodynamic performance.}, url = {https://espace.library.uq.edu.au/data/UQ_9e7ac3e/AFMC2020_Revised_paper_8.pdf?dsi_version=0e6eb909f71efa6567e9e9b41b4939c9\&Expires=1614596146\&Key-Pair-Id=APKAJKNBJ4MJBJNC6NLQ\&Signature=IuB8BRStseU0E-bD3DHcCSeLUzM7V1a4OHeEVpahIDkjCtNIR43ynqKesm15BAQgK5jxRf}, DOI = {https://doi.org/10.14264/9e7ac3e}, author = {Asli, M. and Stathopoulos, P. and Paschereit, C. O.} } @Article { Yücel_2020, title = {Investigation of the fuel distribution in a shockless explosion combustor}, journal = {Journal of Engineering of gas turbines and power}, year = {2020}, volume = {143}, number = {1}, pages = {8}, abstract = {Shockless explosion combustor (SEC) is a promising concept for implementing pressure gain combustion into a conventional gas turbine cycle. This concept aims for a quasi-homogeneous auto-ignition that induces a moderate rise in pressure. Since the ignition is not triggered by an external source but driven primarily by chemical kinetics, the homogeneity of the auto-ignition is very sensitive to local perturbations in equivalence ratio, temperature, and pressure that produce undesired local premature ignition. Therefore, the precise injection of a well-defined fuel profile into a convecting air flow is crucial to ensure a quasi-homogeneous ignition of the entire mixture. The objective of this work is to demonstrate that the injected fuel profile is preserved throughout the entire measurement section. For this, two different control trajectories are investigated. Optical measurement techniques are used to illustrate the effect of turbulent transport and dispersion caused by boundary layer effects on the fuel concentration profile. Results from line-of-sight measurements by tunable diode laser absorption spectroscopy indicate that the transport of the fuel-air mixture is dominated by turbulent diffusion. However, comparisons to numerical calculations reveal the effect of dispersion toward the bounds of the fuel concentration profile. The spatially resolved distributions of the fuel concentration inside the combustor gained from acetone planar laser induced fluorescence (PLIF) replicates a typical velocity distribution of turbulent pipe flow in radial direction visualizing boundary layer effects. Comparing both methods provides deep insights into the transport processes that have an impact on the operation of the SEC.}, note = {GTP-20-1504}, keywords = {Combustion chambers, fuels, lasers, air flow, cycles, explosions, fluorescence}, url = {https://asmedigitalcollection.asme.org/gasturbinespower/article/143/1/011008/1091867/Investigation-of-the-Fuel-Distribution-in-a}, DOI = {https://doi.org/10.1115/1.4049220}, author = {Y{\"u}cel, F. and Habicht, F. and Jaeschke, A. and L{\"u}ckoff, F. and Paschereit, C. O. and Oberleithner, K.} } @Article { Noack20200701, title = {Low-dimensional flow models from high-dimensional flow data with machine learning and first principles}, journal = {ERCIM News}, year = {2020}, number = {122}, pages = {30-31}, abstract = {Reduced-order modelling and system identification can help us figure out the elementary degrees of freedom and theunderlying mechanisms from the high-dimensional and nonlinear dynamics of fluid flow. Machine learning has broughtnew opportunities to these two processes and is revolutionising traditional methods. We show a framework to obtain asparse human-interpretable model from complex high-dimensional data using machine learning and first principles.}, url = {https://ercim-news.ercim.eu/images/stories/EN122/EN122-web.pdf}, ISSN = {0926-4981}, author = {Deng, N. and Pastur, L. R. and Noack, B. R..} } @Article { Noack02102020, title = {Low-order model for successive bifurcations of the fluidic pinball}, journal = {Journal of Fluid Mechanics}, year = {2020}, volume = {884}, number = {A37}, pages = {1-39}, abstract = {We propose the first least-order Galerkin model of an incompressible flow undergoingtwo successive supercritical bifurcations of Hopf and pitchfork type. A key enableris a mean-field consideration exploiting the symmetry of the mean flow and theasymmetry of the fluctuation. These symmetries generalize mean-field theory,e.g. no assumption of slow growth rate is needed. The resulting five-dimensionalGalerkin model successfully describes the phenomenogram of the fluidic pinball, atwo-dimensional wake flow around a cluster of three equidistantly spaced cylinders.The corresponding transition scenario is shown to undergo two successive supercriticalbifurcations, namely a Hopf and a pitchfork bifurcation on the way to chaos. Thegeneralized mean-field Galerkin methodology may be employed to describe othertransition scenarios.}, keywords = {bifurcation, low-dimensional models, wakes}, url = {https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/loworder-model-for-successive-bifurcations-of-the-fluidic-pinball/31E74B80FB2571D10D5166039B991BB3\#}, ISSN = {0022-1120}, DOI = {https://dx.doi.org/10.1017/jfm.2019.959}, author = {Deng, N. and Noack, B. R. and Morzyński, M. and Pastur, L. R.} } @Article { Biedermann_2020, title = {Multi-objective modeling of leading-edge serrations applied to low-pressure axial fans}, journal = {ASME Journal of Engineering for Gas Turbines and Power}, year = {2020}, volume = {142}, number = {11}, pages = {13}, abstract = {A novel modeling strategy is proposed which allows high-accuracy predictions of aerodynamic and aeroacoustic target values for a low-pressure axial fan, equipped with serrated leading edges. Inspired by machine learning processes, the sampling of the experimental space is realized by use of a Latin hypercube design plus a factorial design, providing highly diverse information on the analyzed system. The effects of four influencing parameters (IP) are tested, characterizing the inflow conditions as well as the serration geometry. A total of 65 target values in the time and frequency domains are defined and can be approximated with high accuracy by individual artificial neural networks. Furthermore, the validation of the model against fully independent test points within the experimental space yields a remarkable fit, even for the spectral distribution in 1/3-octave bands, proving the ability of the model to generalize. A metaheuristic multi-objective optimization approach provides two-dimensional Pareto optimal solutions for selected pairs of target values. This is particularly important for reconciling opposing trends, such as the noise reduction capability and aerodynamic performance. The chosen optimization strategy also allows for a customized design of serrated leading edges, tailored to the specific operating conditions of the axial fan.}, note = {GTP-20-1406}, keywords = {Acoustics, Artificial neural networks, Blades, design, fans, flow (dynamics), modeling, noise control, optimization, Pareto optimization, pressure, turbulence, noise (sound), rotors, signals, wavelength}, url = {https://asmedigitalcollection.asme.org/gasturbinespower/article/142/11/111009/1087529/Multi-Objective-Modeling-of-Leading-Edge}, DOI = {https://doi.org/10.1115/1.4048599}, author = {Biedermann, T. M. and Reich, M. and Paschereit, C. O.} } @Article { Bach2019cnf}, title = {Performance analysis of a rotating detonation combustor based on stagnation pressure measurements}, journal = {Combustion and Flame}, year = {2020}, volume = {217}, pages = {21-36}, abstract = {This study explores the effect of differing inlet and outlet boundary conditions on the operation and performance of a rotating detonation combustor (RDC) over an annulus mass flux range of 50 to 210 and equivalence ratios of 0.7, 1.0, and 1.3. The RDC is equipped with either a uniform outlet restriction or with a set of nozzle guide vanes to simulate turbine integration. Stagnation pressure data from Kiel probes placed in the high-enthalpy exhaust flow are presented for the operational envelope. The RDC's operation is categorized into different modes distinguished by the number of co- and counter-rotating combustion waves in the annulus. With increasing mass flux, a typical progression proceeding from a pair of counter-rotating waves, to a single detonation wave, and then further to multiple co-rotating waves is observed with wave speeds reaching up to 84\% of the CJ velocity. It is shown that a choking condition at the outlet throat correlates with the transition from two counter-rotating waves to a single wave detonation regime. The channel Mach number is then calculated from measured pressure ratios and is shown to agree with area ratio-based estimates. The pressure gain of the RDC is expressed as the stagnation pressure change from the air plenum to the outlet throat, and it is shown that the specific operating mode of the device - in conjunction with the chosen injector and outlet area ratios - can significantly decrease the pressure gain performance in some cases, while not significantly affecting it in others. While no positive pressure gain was achieved in the experiments, the presented experimental data compare well with numerical results of similar boundary conditions and underline the importance of minimizing injector pressure loss while applying outlet restrictions to the combustor. The data also suggest that specific geometric combinations may lead to adverse modes such as longitudinally pulsing combustion, resulting in a reduction in the measured pressure gain relative to numerical results. This observation occurs more often for geometric combinations which are the most promising for exhibiting positive pressure gain, and suppressing these modes will be an important topic to achieving this goal. It is further shown that transition regions exist between modes of one and multiple co-rotating waves, and that wave multiplication may be necessary to unlock further increases in the pressure gain.}, url = {https://doi.org/10.1016/j.combustflame.2020.03.017}, ISSN = {0010-2180}, DOI = {10.1016/j.combustflame.2020.03.017}, author = {Bach, E. and Stathopoulos, P. and Paschereit, C. O. and Bohon, M.} } @Article { marten2020predicting, title = {Predicting wind turbine wake breakdown using a free vortex wake code}, journal = {AIAA Journal}, year = {2020}, volume = {58}, number = {11}, pages = {4672-4685}, url = {https://arc.aiaa.org/doi/10.2514/1.J058308}, publisher = {American Institute of Aeronautics and Astronautics}, ISSN = {0001-1452}, DOI = {10.2514/1.J058308}, author = {Marten, D. and Paschereit, C. O. and Huang, X. and Meinke, M. and Schr{\"o}der, W. and M{\"u}ller, J. and Oberleithner, K.} } @Article { Bartholomay2020, title = {Pressure based lift estimation and its application to feedforwardl load control employing trailing edge flaps}, journal = {Wind Energy Science Discussions}, year = {2020}, volume = {20201-39}, abstract = {This experimental load control study presents results of an active trailing edge flap feedforward controller for wind turbine applications. The controller input is derived from pressure based lift estimation methods that rely either on a quasi-steady method, based on a three-hole probe, or on an unsteady method that is based on three selected surface pressure ports. Furthermore, a standard feedback controller, based on force balance measurements, is compared to the feedforward control. A Clark-Y airfoil is employed for the wing that is equipped with a trailing edge flap of x/c = 30 \% chordwise extension. Inflow disturbances are created by a two-dimensional active grid. The Reynolds number is Re = 290,000 and reduced frequencies of k = 0.07 up to k = 0.32 are analyzed. Within the first part of the paper, the lift estimation methods are compared. The surface pressure based method shows generally more accurate results whereas the three-hole probe estimate overpredicts the lift amplitudes with increasing frequencies. Nonetheless, employing the latter as input to the feedforward controller is more promising as a beneficial phase lead is introduced by this method. A successful load alleviation was achieved up to reduced frequencies of k = 0.192.}, url = {https://wes.copernicus.org/preprints/wes-2020-91/}, DOI = {10.5194/wes-2020-91}, author = {Bartholomay, S. and Wester, T. T. B. and Perez-Becker, S. and Konze, S. and Menzel, C. and H{\"o}lling, M. and Spickenheuer, A. and Peinke, J. and Nayeri, C. N. and Paschereit, C. O.. and Oberleithner, K.} } @Article { Müller2020, title = {Receptivity of the turbulent precessing vortex core: Synchronization experiments and global adjoint linear stability analysis}, journal = {Journal of Fluid Mechanics}, year = {2020}, volume = {888}, pages = {A3}, url = {https://www.cambridge.org/core/product/identifier/S0022112019010632/type/journal\{\textbackslash_\}article}, publisher = {Cambridge University Press}, ISSN = {0022-1120}, DOI = {10.1017/jfm.2019.1063}, author = {M{\"u}ller, J. and L{\"u}ckoff, F. and Paredes, P. and Theofilis, V. and Oberleithner, K.} } @Article { paredes-cisneros_simulation_2020, title = {Simulation of hypoxia PET-tracer uptake in tumours: Dependence of clinical uptake-values on transport parameters and arterial input function}, journal = {Physica Medica}, year = {2020}, volume = {70}, pages = {109--117}, url = {https://linkinghub.elsevier.com/retrieve/pii/S1120179720300144}, ISSN = {11201797}, DOI = {10.1016/j.ejmp.2020.01.012}, author = {Paredes-Cisneros, I. and Karger, C. and Caprile, P. and Nolte, D. and Espinoza, I. and Gago-Arias, A.} } @Article { Vanierschot2020, title = {Single- and double-helix vortex breakdown as two dominant global modes in turbulent swirling jet flow}, journal = {Journal of Fluid Mechanics}, year = {2020}, volume = {883}, pages = {A31}, url = {https://www.cambridge.org/core/product/identifier/S0022112019008723/type/journal\{\textbackslash_\}article}, publisher = {Cambridge University Press (CUP)}, ISSN = {0022-1120}, DOI = {10.1017/jfm.2019.872}, author = {Vanierschot, M. and M{\"u}ller, J. and Sieber, M. and Percin, M. and van Oudheusden, B. and Oberleithner, K.} } @Article { Bluemner2019symp}, title = {Stabilization mechanisms of longitudinal pulsations in rotating detonation combustors (in press)}, journal = {Proceedings of the Combustion Institute}, year = {2020}, DOI = {10.1016/j.proci.2020.07.063}, author = {Bl{\"u}mner, R. and Gutmark, E. and Paschereit, C. O. and Bohon, M.} } @Article { Soto-Valle2020, title = {Wind turbine tip vortices under the influence of wind tunnel blockage effects}, journal = {Journal of Physics: Conference Series}, year = {2020}, volume = {1618}, pages = {032045}, abstract = {The current paper describes the characteristics of the tip vortex in the near wake of a three-bladed upwind horizontal axis wind turbine with arotor diameter of 3 m. Phase-locked stereo particle image velocimetry measurements were carried out under the inuence of the windtunnel walls that create a high blockage ratio. The location of the vortex, convection velocity, core radius, and strength were investigated and compared with similar investigations, including dierent blockages cases. Additionally, the same performance of the wind turbine model wassimulated in the open source wind turbine tool QBlade, using the lifting line free vortex wake module in the absence of the walls.The results showed that the location of the tip vortices was more inboard the tip and more downstream the tunnel compared to the simulations and similar experiments. The convection velocity remained similar in the axial direction and changed in the lateral direction, contributingto the delay of the movement of the tip vortex outboard the tip. The strength, based on the circulation, was found with a dierence of 4\% between simulation and experiment.�}, url = {https://doi.org/10.1088/1742-6596/1618/3/032045}, DOI = {10.1088/1742-6596/1618/3/032045}, author = {Soto-Valle, R. and Alber, J. and Manolesos, M. and Nayeri, C. N. and Paschereit, C. O.} } @Conference { Noack_2020, title = {Active flow control with unsteady coanda actuation on a high-lift conguration}, year = {2020}, month = {1}, day = {6}, keywords = {active flow control, Coanda blowing, piezo actuator}, url = {https://elib.dlr.de/127971/}, organization = {AIAA}, event_place = {Orlando, Fl. USA}, event_name = {AIAA SciTech Forum}, event_date = {6-1-2020}, author = {El-Sayed, Y. and Gomes de Paula, N. and Genest, B. and Semaan, R. and Radespiel, J. and Petersen, R. and Behr, C. and Wierach, P. and Noack, B. R.} } @Inproceedings { rezay2020evaluation, title = {Evaluation of shock dividers using numerical and experimental methods}, year = {2020}, pages = {926}, url = {https://arc.aiaa.org/doi/10.2514/6.2020-0926}, publisher = {American Institute of Aeronautics and Astronautics}, address = {Reston, Virginia}, booktitle = {AIAA Scitech 2020 Forum}, ISBN = {978-1-62410-595-1}, DOI = {10.2514/6.2020-0926}, author = {Rezay Haghdoost, M. and Thethy, B. and Nadolski, M. and Klein, R. and Honnery, D. and Edgington-Mitchell, D. and Seo, B. and Paschereit, C. O. and Oberleithner, K.} } @Inproceedings { Bluemner2020scitech}, title = {Investigation of longitudinal operating modes in rotating detonation combustors}, year = {2020}, address = {Orlando, FL}, booktitle = {AIAA Paper 2020-2287}, DOI = {10.2514/6.2020-2287}, author = {Bl{\"u}mner, R. and Paschereit, C. O. and Gutmark, E. and Bohon, M.} } @Inproceedings { Bach2020scitech, title = {RDC Operation and Performance with Varying Air Injector Pressure Loss}, year = {2020}, address = {Orlando, FL}, booktitle = {AIAA Paper 2020-0199}, DOI = {10.2514/6.2020-0199}, author = {Bach, E. and Paschereit, C. O. and Stathopoulos, P. and Bohon, M.} } @Inproceedings { thethy2020redistribution, title = {Redistribution of transient shock waves using shock dividers}, year = {2020}, pages = {925}, url = {https://arc.aiaa.org/doi/10.2514/6.2020-0925}, publisher = {American Institute of Aeronautics and Astronautics}, address = {Reston, Virginia}, booktitle = {AIAA Scitech 2020 Forum}, ISBN = {978-1-62410-595-1}, DOI = {10.2514/6.2020-0925}, author = {Thethy, B. and Rezay Haghdoost, M. and Paschereit, C. O. and Honnery, D. and Edgington-Mitchell, D. and Oberleithner, Kilian} } @Article { Jentzsch_2019, title = {Development of a setup and measurement procedure for unsteady model velocities in a large water towing tank}, journal = {ARC, AIAA}, year = {2019}, month = {1}, day = {6}, url = {https://arc.aiaa.org/doi/pdf/10.2514/6.2019-2164}, DOI = {10.2514/6.2019-2164}, author = {Jentzsch, M. and Schmidt, H. J. and Woszidlo, R. and Nayeri, C. N. and Paschereit, C. O.} } @Article { Tschepe2019_1, title = {Analysis of moving model experiments in a towing tank for aerodynamic drag measurement of high-speed trains}, journal = {Springer}, year = {2019}, pages = {16}, abstract = {The present study assesses the applicability of towing tank experiments using a moving model for the investigation of the aerodynamics of long land-borne heavy vehicles such as buses, trucks, and trains. Based on experiments with a 1:22 scaled model of a high-speed train, the influence of various conditions relevant for the transferability of the results obtained in water to air is analysed exemplarily. These conditions include surface waves, cavitation and submergence depth. The experiments were carried out in the shallow water towing tank of the Technische Universit{\"a}t Berlin. It is shown that outside a critical Froude number range of about 0.2 < Fr < 1.2 the impact of the surface waves can be neglected and no cavitation appears in the velocity range investigated. Furthermore, a correction method is proposed taking into account the bias through surface waves at small submergence and thus allowing for a wider Froude number range. The data obtained in the towing tank are found to be in excellent agreement to other investigation methods.}, url = {https://link.springer.com/article/10.1007/s00348-019-2748-8}, language = {English}, ISSN = {0723-4864}, DOI = {10.1007/s00348-019-2748-8}, author = {Tschepe, J. and Nayeri, C. N. and Paschereit, C. O.} } @Article { Marten2019, title = {Benchmark of a novel aero-elastic simulation code for small scale VAWT analysis}, journal = {ASME}, year = {2019}, volume = {141}, number = {4}, pages = {13}, abstract = {After almost 20 years of absence from research agendas, interest in the vertical axis wind turbine (VAWT) technology is presently increasing again, after the research stalled in the mid 90's in favor of horizontal axis wind turbines (HAWTs). However, due to the lack of research in past years, there are a significantly lower number of design and certification tools available, many of which are underdeveloped if compared to the corresponding tools for HAWTs. To partially fulfill this gap, a structural finite element analysis (FEA) model, based on the Open Source multiphysics library PROJECT::CHRONO, was recently integrated with the lifting line free vortex wake (LLFVW) method inside the Open Source wind turbine simulation code QBlade and validated against numerical and experimental data of the SANDIA 34 m rotor. In this work, some details about the newly implemented nonlinear structural model and its coupling to the aerodynamic solver are first given. Then, in a continuous effort to assess its accuracy, the code capabilities were here tested on a small-scale, fast-spinning (up to 450 rpm) VAWT. The study turbine is a helix shaped, 1 kW Darrieus turbine, for which other numerical analyses were available from a previous study, including the results coming from both a one-dimensional beam element model and a more sophisticated shell element model. The resulting data represented an excellent basis for comparison and validation of the new aero-elastic coupling in QBlade. Based on the structural and aerodynamic data of the study turbine, an aero-elastic model was then constructed. A purely aerodynamic comparison to experimental data and a blade element momentum (BEM) simulation represented the benchmark for QBlade aerodynamic performance. Then, a purely structural analysis was carried out and compared to the numerical results from the former. After the code validation, an aero-elastically coupled simulation of a rotor self-start has been performed to demonstrate the capabilities of the newly developed model to predict the highly nonlinear transient aerodynamic and structural rotor response.}, note = {GTP-18-1489}, keywords = {Blades, Rotors, Simulation, Turbines, Vertical axis wind turbines, Modal analysis, Flow (Dynamics), Vortices}, url = {https://asmedigitalcollection.asme.org/gasturbinespower/article/141/4/041014/367187/Benchmark-of-a-Novel-Aero-Elastic-Simulation-Code}, language = {English}, DOI = {doi.org/10.1115/1.4041519}, author = {Marten, D. and Lenni, M. and Pechlivanoglu, G. and Paschereit, C. O. and Bianchini, A. and Ferrara, A. and Ferrari, L.} } @Article { Tanneberger2019, title = {Combustion efficiency measurements and burner characterization in a hydrogen-oxyfuel combustor}, journal = {International Journal of Hydrogen Energy}, year = {2019}, keywords = {Oxy-fuel combustion, Hydrogen, Steam dilution, Combustion efficiency, Large scale energy storage}, url = {http://www.sciencedirect.com/science/article/pii/S0360319919318865}, ISSN = {0360-3199}, DOI = {https://doi.org/10.1016/j.ijhydene.2019.05.055}, author = {Tanneberger, T. and Schimek, S. and Paschereit, C. O. and Stathopoulos, P.} } @Article { Blümner_2019, title = {Counter-rotating wave mode transition dynamics in an RDC}, journal = {International Journal of Hydrogen Energy}, year = {2019}, volume = {44}, pages = {7628 - 7641}, abstract = {This work describes an experimental study on the transition dynamics in a hydrogen-air RDC as the operating mode transitions from two steadily propagating, equally-fast counter-rotating waves to a single wave depending on the operating condition. The operating mode for a range of equivalence ratios and mass flow rates is investigated based on time-resolved measurements of the pressure in the combustor annulus at multiple azimuthal locations, as well as based on simultaneous measurements of the natural flame luminosity from the aft end of the RDC. Overall reactant mass flow and equivalence ratio, coupled with the plenum pressures, were confirmed as the driving parameters for wave mode transition. Further experimentation is necessary to decouple these effects, however the results illustrate complex transition dynamics, yielding an acceleration of the primary wave and the simultaneous deceleration of the secondary wave(s). At the same time the secondary wave number is observed to increase up to a triplet of counter-rotating waves. A non-dimensional wave dominance parameter is proposed, which links the relative wave speeds of the waves to thermodynamic properties of the combustor. It indicates regimes of constant wave mode that are independent of changing operating conditions and that extend far into the operating map for the given RDC geometry. The results further indicate a correlation between the operating mode with two counter-rotating waves and choked flames, as well as quasi-detonations observed in generic detonation experiments in the literature.}, url = {https://doi.org/10.1016/j.ijhydene.2019.01.262}, language = {English}, DOI = {10.1016/j.ijhydene.2019.01.262}, author = {Bl{\"u}mner, R. and Bohon, M. and Paschereit, C. O. and Gutmark, E. J.} } @Article { Tanneberger_2019, title = {Efficiency Measurement Approach for a Hydrogen Oxyfuel Combustor}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2019}, volume = {141}, number = {10}, url = {https://doi.org/10.1115/1.4044779}, ISSN = {0742-4795}, DOI = {10.1115/1.4044779}, author = {Tanneberger, T. and Schimek, S. and Paschereit, C. O. and Stathopoulos, P.} } @Article { Holst2019, title = {Experimental analysis of a NACA 0021 airfoil section through 180-deg angle of attack at low Reynolds numbers for use in wind turbine analysis}, journal = {ASME}, year = {2019}, volume = {141}, number = {4}, pages = {12}, abstract = {Wind turbine industry has a special need for accurate post stall airfoil data. While literature often covers incidence ranges [−10 deg, +25 deg], smaller machines experience a range of up to 90 deg for horizontal axis and up to 360 deg for vertical axis wind turbines (VAWTs). The post stall data of airfoils is crucial to improve the prediction of the start-up behavior as well as the performance at low tip speed ratios. The present paper analyzes and discusses the performance of the symmetrical NACA 0021 airfoil at three Reynolds numbers (Re = 100 k, 140 k, and 180 k) through 180 deg incidence. The typical problem of blockage within a wind tunnel was avoided using an open test section. The experiments were conducted in terms of surface pressure distribution over the airfoil for a tripped and a baseline configuration. The pressure was used to gain lift, pressure drag, moment data. Further investigations with positive and negative pitching revealed a second hysteresis loop in the deep post stall region resulting in a difference of 0.2 in moment coefficient and 0.5 in lift.}, note = {GTP-18-1576}, keywords = {Airfoils, Pressure, Reynolds number, Wind turbines, Experimental analysis, Wind tunnels, Drag (Fluid dynamics)}, url = {https://doi.org/10.1115/1.4041651}, language = {English}, DOI = {10.1115/1.4041651}, author = {Holst, D. and Church, B. and Pechlivanoglu, G., and T{\"u}z{\"u}ner, E. and Saverin, J. and Nayeri, C. N. and Paschereit, C. O.} } @Article { Blümner2019, title = {Generation and transport of equivalence ratio fluctuations in an acoustically forced swirl burner}, journal = {Combustion and Flame}, year = {2019}, volume = {209}, pages = {99 - 116}, abstract = {In the context of thermoacoustic instabilities, knowledge about the generation and transport of equivalence ratio fluctuations is highly important to correctly model their impact on the flame transfer function. In this work, spatially resolved equivalence ratio perturbations in the mixing section of an acoustically forced, partially premixed swirl burner typical of modern gas turbine combustors are investigated. Tunable diode laser absorption spectroscopy using a wavelength-modulation approach is applied to assess the spatially inhomogeneous equivalence ratio field in the radial direction. Particle image velocimetry is applied to measure the axial velocity field. Based on these results, a tomographic reconstruction is utilized to deduce the local fuel distribution at two axial locations. Integrated, global equivalence ratio fluctuations are calculated and compared to simple line-of-sight measurements. The influence of the forcing frequency and amplitude is investigated and good agreement was found between the different measurement approaches. Frequency dependent equivalence ratio perturbation generation mechanisms driven by air velocity fluctuations in the swirler, as well as pressure fluctuations at the fuel injector, are observed. Two different mixing transfer functions modeling diffusion and dispersion are compared to the results and reveal substantial differences, indicating a significant impact of coherent fluctuations of the transport velocity on the mixing that are not accounted for by either of the models.}, keywords = {Thermoacoustic instability, Equivalence ratio, Swirl burner, Laser absorption spectroscopy, Mixing}, url = {https://doi.org/10.1016/j.combustflame.2019.07.007}, language = {English}, DOI = {10.1016/j.combustflame.2019.07.007}, author = {Bl{\"u}mner, R. and Paschereit, C. O. and Oberleithner, K.} } @Article { Bohon2019, title = {High-speed imaging of wave modes in an RDC}, journal = {Experimental Thermal and Fluid Science}, year = {2019}, volume = {102}, pages = {28 - 37}, abstract = {Various operating modes have been observed in the rotating detonation combustor (RDC) studied here, as well as by others. These modes can be generally categorized into two groups: one or more co-rotating waves and counter-rotating waves. The combustor is able to stabilize both types of operation, however the stabilization mechanism remains unclear. In order to better understand these cases, these operational modes are investigated with high-speed pressure transducers installed in the combustor annulus combined with simultaneous high-speed video imaging of the natural luminosity of the detonation wave from the aft end of the RDC. These results confirm the operation in both the steady single wave mode as well as the counter-rotating waves mode. The presence of this mode further demonstrates the complex dynamics inherent in the stabilization of the detonation wave. As each wave propagates, they initially begin to weaken followed by re-strengthening after collision which serves to stabilize the mode. Differences in the velocities of the waves was also observed to result in a beating phenomenon expressed as an amplitude modulation of the pressure traces. High-speed video imaging of the high-temperature emission from H2O in the RDC annulus was used in conjunction with the pressure traces for a range of flow rates and equivalence ratios. Processing of the images into the wave frame of reference allowed for the identification of the average luminosity profile, characterized by a steep increase in natural luminosity near the wave front, followed by a trailing tail extending approximately half the annulus perimeter.}, keywords = {Rotating detonation high-speed video wave modes counter-rotating waves}, url = {https://doi.org/10.1016/j.expthermflusci.2018.10.031}, language = {English}, DOI = {10.1016/j.expthermflusci.2018.10.031}, author = {Bohon, M. and Bl{\"u}mner, R. and Paschereit, C. O. and Gutmark, E. J.} } @Article { Zhang2019, title = {Impact of combustion modeling on the spectral response of heat release in LES}, journal = {Combustion Science and Technology}, year = {2019}, volume = {191}, pages = {1520 - 1540}, abstract = {This work assesses the effect of using different closure concepts for the spatially filtered mean reaction rate on the resolved spectral response of turbulent heat release in large eddy simulations (LESs). Two well-known combustion models, the turbulent flame speed closure (TFC) and the dynamically thickened flame (DTF) models have been applied to a premixed turbulent jet flame with otherwise identical numerical setups. Although the flame front is artificially thickened in the DTF model, it reproduces a thinner flame and, hence, stronger flame-turbulence interactions compared to the TFC model. As the time-averaged quantities from both methods are comparable, the DTF approach shows overall higher fluctuations of local and integral heat release rates in the spectral domain compared to the TFC model, particularly in the high-frequency range. A better agreement with measured sound pressure density is observed for TFC in the low-frequency range and for DTF in the high-frequency range. TFC simulations with different source formulations, that is, \(\omega\)˙¯¯c\(\propto\)c˜(1−c˜) and \(\omega\)˙¯¯c\(\propto\)∣∣∇c˜∣∣, showed comparable flame thicknesses and spectra of heat release, but the averaged flow quantities calculated with \(\omega\)˙¯¯c\(\propto\)∣∣∇c˜∣∣, however, deviate largely from measured data for the current setup. In the second step, the same formulations for the mean rate are applied to an excited plane-jet flame (two-dimensional (2D)) using equidistant grid cells and forced inflow conditions, thereby excluding the influence of varying grid resolution and broadband turbulent fluctuations. This setup is specifically tailored for a detailed analysis of flame response to flow unsteadiness and grid resolution. The formulation of the reaction rate according to the TFC approach again results in a considerably thicker flame compared to results obtained from the DTF model and direct numerical simulation, even on a sufficiently fine mesh. Therefore, the DTF formulation of the reaction rate shows overall stronger responses of heat release rates to forced fluctuations than the TFC formulation. Differences are smaller in the low-frequency range, indicating a stronger damping of heat release fluctuations with increasing frequency for the TFC formulation. Coarsening the grid leads to a much stronger damping of heat release fluctuations in the DTF formulation compared with the TFC formulation, so that the benefit of the DTF formulation decreases with decreasing grid resolution. This reflects the different sensitivity behavior of these models with respect to unsteady flows and grid resolutions, which is of great importance for computing thermoacoustic problems with LES, for example, combustion noise.}, keywords = {Large eddy simulation, turbulent premixed flame, turbulent flame speed, thickened flame approach, OpenFOAM}, url = {https://doi.org/10.1080/00102202.2018.1558218}, language = {English}, DOI = {10.1080/00102202.2018.1558218}, author = {Zhang, F. and Zirwes, T. and Habisreuther, P. and Bockhorn, H. and Dimosthenis, T. and Nawroth, H. and Paschereit, C. O.} } @Article { Tschepe'2019, title = {Investigation of high-speed train drag with towing tank experiments and CFD}, journal = {Chalmers Research Publications}, year = {2019}, volume = {102}, pages = {417 - 434}, abstract = {In order to assess the accuracy of drag prediction methods for high-speed trains, experimental and numerical investigations were performed. Besides the drag coefficient, skin friction and pressure distributions on and near the model have been measured for a 1:22 model of the ICE/V. For the experiments, a moving model rig called DIWA (Drag measurement in water) was realised in a 120 m long towing tank to allow for a realistic simulation of the flow around the train, even in the underbelly region. Numerical investigations were performed using Partially-averaged Navier-Stokes (PANS) simulations based on the k-\(\omega\)-SST turbulence model. Both experimental and numerical methods can be considered as a novelty in the field of train aerodynamics. The results are compared with data from full-scale tests. It is shown, that the moving model rig DIWA allows for the measurement of drag coefficients of trains with high accuracy. Furthermore, the data acquired using the PANS approach compares well with the experimental data.}, keywords = {Towing tank, Train aerodynamics, Drag measurement, PANS, Moving model}, url = {https://research.chalmers.se/en/publication/510116}, ISSN = {1386-6184}, DOI = {10.1007/s10494-018-9962-y}, author = {Tschepe, J. and Fischer, D. and Nayeri, C. N. and Paschereit, C. O. and Krajnovic, S.} } @Article { Pampaloni2019, title = {Large-Eddy-Simulation modeling of the flame describing function of a lean-premixed swirl-stabilized flame}, journal = {Journal of Propulsion and Power}, year = {2019}, volume = {35}, pages = {994 - 1004}, abstract = {The prediction of thermo-acoustic instabilities is of paramount importance for gas-turbine combustion systems to meet the emission and efficiency targets. To predict the frequencies and amplitudes of pressure oscillations, and as a consequence, their impact on engine reliability, the nonlinear behavior of the system should be studied. An atmospheric lean-premixed combustor has been numerically investigated for validation purposes. A decoupled approach, separating the acoustic behavior and the nonlinear flame response, which is represented in this work by the flame describing function, has been used. As the first step, the flame describing function calculation from large-eddy simulations has been validated, including the effects of flame stretch and heat loss into the turbulence combustion model. Then, frequency-domain calculations using a three-dimensional Helmholtz solver have been carried out, and results have been validated against experimental measurements and a self-excited large-eddy simulation.}, url = {https://apps.webofknowledge.com/full_record.do?product=WOS\&search_mode=GeneralSearch\&qid=10\&SID=C4u2D5PtIHZKOxMnzhi\&page=1\&doc=2\&cacheurlFromRightClick=no}, language = {English}, ISSN = {0748-4658}, DOI = {10.2514/1.B37490}, author = {Pampaloni, D. and Andreini, A. and Faccini, B. and Paschereit, C. O.} } @Article { Bohon_2019, title = {Measuring rotating detonation combustion using cross-correlation}, journal = {Springer}, year = {2019}, volume = {103}, pages = {217 - 292}, abstract = {The cyclic propagation of detonation waves in the Rotating Detonation Combustor (RDC) make it an ideal candidate for using the cross-correlation technique. However, the potential for complicated operating modes combined with difficult diagnostic access introduces the possibility for ambiguous outcomes of the analysis. This work will first consider the specific details of the application of the technique to analyzing the features of RDC operation, including wave speed, direction, and operating mode. The accuracy and limitations of the technique will be quantified from a theoretical perspective. The second half of the work will focus on several example run conditions and operating modes in the RDC and will highlight differences in the analysis of variable combustion modes. From these cases studies, it is clear that a great deal of insight on the operation can be gleaned from analyzing the correlation. However, care must be taken in the experimental setup and analysis as a poorly designed approach can easily yield deceptive results. Finally, guidelines for preparing the experiment and conducting the analysis are provided to improve the quality of the results.}, keywords = {Cross-correlation Rotating detonation combustion Operating modes Wave speed}, url = {https://link.springer.com/article/10.1007/s10494-019-00017-z}, language = {English}, DOI = {10.1007/s10494-019-00017-z}, author = {Bohon, M. and Bl{\"u}mner, R. and Paschereit, C. O. and Gutmark, E. J.} } @Article { Lückoff2019, title = {Phase-opposition control of the precessing vortex core in turbulent swirl flames for investigation of mixing and flame stability}, journal = {ASME}, year = {2019}, volume = {141}, number = {J. Eng. Gas Turbines Power. Nov 2019, 141(11): 111008 (10 pages)}, pages = {10}, abstract = {The precessing vortex core (PVC) is a helically shaped coherent flow structure that occurs in reacting and nonreacting swirling flows undergoing vortex breakdown. Inswirl-stabilized combustors, the PVC affects important phenomena, such as turbulent mixing and thermoacoustic oscillations. In this work, a closed-loop flow control system is developed, which allows for phase-opposition control of the PVC, to achieve appropriateconditions to systematically investigate the influence of the PVC on turbulent flames. The control consists of a zero-net-mass-flux actuator placed in the mixing section of the com-bustor, where the PVC is most receptive to periodic forcing. The flow control system is characterized from pressure measurements and particle image velocimetry (PIV) and the impact on flame dynamics is extracted from OH*-chemiluminescence measurements. The data reveal that the PVC amplitude is considerably suppressed by the phase-oppositioncontrol without changing the overall characteristics of flow and flame, which is crucial to study the exclusive effect of the PVC on combustion processes. Moreover, the control allows the PVC amplitude to be adjusted gradually to investigate the PVC impact on turbulent mixing and flame dynamics. It is revealed that the PVC-induced flow fluctuations mainly affect the large-scale mixing, while the small scale mixing remains unchanged.This is because the suppression of the PVC allows other modes to become more dominantand the overall turbulent kinetic energy (TKE) budget remains unchanged. The destabilization of other modes, such as the axisymmetric mode, may have some implications on thermoacoustic instability.[DOI: 10.1115/1.4044469]Keywords: active flow control, closed-loop control, precessing vortex core, spectral proper orthogonal decomposition (SPOD), swirl-stabilized combustion, particle image velocimetry (PIV)}, note = {GTP-19-1377}, keywords = {active flow control, closed-loop control, precessing vortex core, spectral proper orthogonal decomposition (SPOD), swirl-stabilized combustion, particle image velocimetry (PIV)}, url = {https://asmedigitalcollection.asme.org/gasturbinespower/article/141/11/111008/975561/Phase-Opposition-Control-of-the-Precessing-Vortex}, language = {English}, DOI = {Journal of Engineering for Gas Turbines and Power}, author = {L{\"u}ckoff, F. and Sieber, M. and Paschereit, C. O. and Oberleithner, K.} } @Article { Saurabh2019, title = {Premixed flame dynamics in response to two-dimensional acoustic forcing}, journal = {Combustion Science and Technology}, year = {2019}, pages = {1184 - 1200}, abstract = {Thermoacoustic instability in annular combustors involves feedback interaction between individual (acoustically compact) flames and - predominantly - azimuthal acoustic modes of the annular combustion chamber. During such an interaction, the flames experience acoustic pressure fluctuations in the combustor and transverse acoustic velocity fluctuations simultaneously. To investigate the dynamics of premixed swirl flames under the influence of transverse acoustics, experiments were performed on a single-burner atmospheric combustion rig with controlled simultaneous axial and transverse acoustic forcing, where the axial acoustics simulates the effect of acoustic pressure fluctuations in the combustor. In this paper, we present results on the descriptive analysis of spatially resolved flame surface fluctuations, acquired via OH-PLIF (OH* planar laser-induced florescence) diagnostics of the forced flame and establish the role of the interaction among coherent structures generated by axial and transverse velocity components in generating global flame response changes with respect to the phase difference between axial and transverse acoustic forcing as reported recently (Saurabh and Paschereit, Combustion Flame 182, 2017).}, keywords = {Thermoacoustic Instability, Annular Combustors, Premixed Swirl Flames, Transverse Acoustics, Flame Response, OH PLIF}, url = {https://doi.org/10.1080/00102202.2018.1516648}, language = {English}, DOI = {10.1080/00102202.2018.1516648}, author = {Saurabh, A. and Paschereit, C. O.} } @Article { Holst_2019, title = {Static and dynamic analysis of a NACA 0021 airfoil Section at low reynolds numbers based on experiments and computational fluidynamics}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2019}, volume = {141}, pages = {10}, abstract = {The wind industry needs airfoil data for ranges of angle of attack (AoA) much wider than those of aviation applications, since large portions of the blades may operate in stalled conditions for a significant part of their lives. Vertical axis wind turbines (VARTs) are even more affected by this need, since data sets across the full incidence range of 180 deg are necessary for a correct performance prediction at different tip-speed ratios. However, the relevant technical literature lacks data in deep and poststall regions for nearly every airfoil. Within this context, the present study shows experimental and numerical results for the well-known NACA 0021 airfoil, which is often used for Darrieus VAWT design. Experimental data were obtained through dedicated wind tunnel measurements of a NACA 0021 airfoil with surface pressure taps, which provided further insight into the pressure coefficient distribution across a wide range of AoAs. The measurements were conducted at two different Reynolds numbers (Re = 140 k and Re = 180 k): each experiment was performed multiple times to ensure repeatability. Dynamic AoA changes were also investigated at multiple reduced frequencies. Moreover, dedicated unsteady numerical simulations were carried out on the same airfoil shape to reproduce both the static polars of the airfoil and some relevant dynamic AoA variation cycles tested in the experiments. The solved flow field was their exploited both to get further insight into the flow mechanisms highlighted by the wind tunnel tests and to provide correction factors to discard the influence of the experimental apparatus, making experiments representative of open-field behavior. The present study is then thought to provide the scientific community with high quality, low-Reynolds airfoil data, which may enable in the near future a more effective design of Darrieus VAWTs.}, note = {GTP-18-1435}, keywords = {Airfoils, Computational fluid dynamics, Flow (Dynamics), Pressure, Reynolds number, Simulation, Wind tunnels, Blades, Cycles, Engineering simulation}, url = {https://doi.org/10.1115/1.4041150}, ISSN = {0742-4795}, DOI = {10.11115/1.4041150}, author = {Holst, D. and Balduzzi, F. and Bianchini, A. and Church, B. and Wegner, F. and Pechlivanoglou, G. and Ferrari, L. and Ferrara, G. and Nayeri, C. N. and Paschereit, C. O.} } @Article { Ostermann2019, title = {The interaction between a spatially oscillating jet emitted by a fluidic oscillator and a cross flow}, journal = {Journal of Fluid Mechanics}, year = {2019}, volume = {863}, pages = {215 - 241}, abstract = {This experimental study investigates the fundamental flow field of a spatially oscillating jet emitted by a fluidic oscillator into an attached cross-flow. Dominant flow structures, such as the jet trajectory and dynamics of streamwise vortices, are discussed in detail with the aim of understanding the interaction between the spatially oscillating jet and the cross-flow. The oscillating jet is ejected perpendicular to the cross-flow. A moveable stereoscopic particle image velocimetry (PIV) system is employed for the plane-by-plane acquisition of the flow field. The three-dimensional, time-resolved flow field is obtained by phase averaging the PIV results based on a pressure signal from inside the fluidic oscillator. The influence of velocity ratio and Strouhal number is assessed. Compared to a common steady wall-normal jet, the spatially oscillating jet penetrates to a lesser extent into the cross-flow's wall-normal direction in favour of a considerable spanwise penetration. The flow field is dominated by streamwise-oriented vortices, which are convected downstream at the speed of the cross-flow. The vortex dynamics exhibits a strong dependence on the Strouhal number. For small Strouhal numbers, the spatially oscillating jet acts similar to a vortex-generating jet with a time-dependent deflection angle. Accordingly, it forms time-dependent streamwise vortices. For higher Strouhal numbers, the cross-flow is not able to follow the motion of the jet, which results in a quasi-steady wake that forms downstream of the jet. The results suggest that the flow field approaches a quasi-steady behaviour when further increasing the Strouhal number.}, keywords = {fluid oscillator ; jets ; flow field ; cross-flow ; fluidischer Oszillator}, url = {https://depositonce.tu-berlin.de//handle/11303/9074}, language = {English}, ISSN = {0022-1120}, DOI = {10.1017/jfm.2018.981}, author = {Ostermann, F. and Woszidlo, R. and Nayeri, C. N. and Paschereit, C. O.} } @Inbook { Ostermann2019, title = {Interaction between a jet emitted by a fluidic oscillator and a cossflow at a skew angle}, year = {2019}, month = {1}, day = {6}, url = {https://arc.aiaa.org/doi/abs/10.2514/6.2019-0887}, publisher = {AIAA SciTech Forum}, DOI = {10.2514/6.2019-0887}, author = {Ostermann, F. and Woszidlo, R. and Nayeri, C. N. and Paschereit, C. O.} } @Article { Schmidt2018, title = {The effect of flow control on the wake dynamics of a rectangular bluff body in ground proximity}, journal = {Experiments in Fluids}, year = {2018}, month = {6}, abstract = {The time-resolved flow field in the wake of a rectangular bluff body in ground proximity is examined through wind tunnel experiments. In addition to an extensive assessment of the baseline wake dynamics, the study also investigates the impact of passive (i.e., base flaps) and active (i.e., fluidic oscillators) flow control on the wake dynamics. The velocity field downstream of the model is acquired with a stereoscopic high-speed particle image velocimetry system at several streamwise and crosswise sections. Coherent wake structures are determined by conditional averaging, spectral analysis, and spectral proper orthogonal decomposition. The baseline flow field is dominated by a wake bi-stability that is characterized by a random shift between two stable wake states. The bi-stability is governed by the model's aspect ratio and occurs in the vertical direction, because the model height is 1.35 times larger than its width. Higher frequency modes with less energy content as determined in the appropriate literature are identified and visualized. A coupling between these modes and the bi-stability is discussed. Flow control has a significant impact on the wake dynamics. When passive flow control is applied, the bi-stability of the wake is still present for a flap angle of 20∘. The higher frequency modes are still detectable but weakened. The turbulence intensity is significantly reduced when the flow attaches to the base flaps and the bi-stability is inhibited. When active flow control is applied, the higher baseline frequencies are suppressed in addition to the absence of the bi-stability. Solely the dominant mode at a Strouhal number of about 0.08 remains present for all flow control configurations. This mode is attributed to an alternating shear layer oscillation.}, url = {https://link.springer.com/article/10.1007\%2Fs00348-018-2560-x}, ISSN = {1432-1114}, DOI = {10.1007/s00348-018-2560-x}, author = {Schmidt, H.-J. and Woszidlo, R. and Nayeri, C. N. and Paschereit, C. O.} } @Article { Stangfeld2018, title = {Mechanism of vortex perturbation via unsteady pitching}, journal = {Aeorspace Research Central, AIAA}, year = {2018}, month = {5}, pages = {8}, abstract = {Experiments indicate that vortices trailing finite wings can be perturbed by periodic wing pitching, leading to rapid dissipation and bursting. To illustrate the perturbation mechanism, Betz vortex rollup relations are combined with the Theodorsen theory for unsteady lift response. A sinusoidal pitch motion on a rigid elliptic planform wing is computed in this study as one example. Pitching modifies the instantaneous lift due to the planform variations, via the reduced frequency, and the rollup relations are applied to low-frequency experimental conditions. The combined Betz-Theodorsen theory shows that relatively large spanwise perturbations of the vortex centers can be achieved and may accelerate the exponential growth associated with the Crow instability. In fact, 84.2 \% of the displacement of the unsteady trailing vortices due to unsteady pitching is oriented in the direction of the Crow instability. Furthermore, the axial velocity in the vortex center, calculated based on the Batchelor method, varies on the order of the flight speed. This forms two types of stagnation points produced by approaching and retreating axial core velocities; in the former case, conservation of mass leads to observations of ''bursting.'' This observation can be explained adequately on the basis of quasi-steady considerations.}, url = {https://arc.aiaa.org/doi/10.2514/1.C034646}, ISSN = {0021-8669 (print) or 1533-3868 (online)}, DOI = {https://doi.org/10.2514/1.C034646}, author = {Strangfeld, C. and Nayeri, C. N. and Paschereit, C. O. and Greenblatt, S.} } @Article { Saverin2018, title = {Comparison of experimental and numerically predicted three-dimensional wake behaviour of a vertical axis wind turbine}, journal = {Journal of Engineering Gas Turbine Power}, year = {2018}, month = {4}, pages = {12}, abstract = {The evolution of the wake of a wind turbine contributes significantly to its operation and performance, as well as to those of machines installed in the vicinity. The inherent unsteady and three-dimensional aerodynamics of Vertical Axis Wind Turbines (VAWT) have hitherto limited the research on wake evolution. In this paper the wakes of both a troposkien and a H-type VAWT rotor are investigated by comparing experiments and calculations. Experiments were carried out in the large-scale wind tunnel of the Politecnico di Milano, where unsteady velocity measurements in the wake were performed by means of hot wire anemometry. The geometry of the rotors was reconstructed in the open-source wind-turbine software QBlade, developed at the TU Berlin. The aerodynamic model makes use of a lifting line free-vortex wake (LLFVW) formulation, including an adapted Beddoes-Leishman unsteady aerodynamic model; airfoil polars are introduced to assign sectional lift and drag coefficients. A wake sensitivity analysis was carried out to maximize the reliability of wake predictions. The calculations are shown to reproduce several wake features observed in the experiments, including blade-tip vortex, dominant and submissive vortical structures, and periodic unsteadiness caused by sectional dynamic stall. The experimental assessment of the simulations illustrates that the LLFVW model is capable of predicting the unsteady wake development with very limited computational cost, thus making the model ideal for the design and optimization of VAWTs.}, note = {GTP-17-1608}, url = {http://gasturbinespower.asmedigitalcollection.asme.org/article.aspx?articleid=2678430}, DOI = {10.1115/1.4039935}, author = {Saverin, J. and Marten, D. and Holst, D. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O. and Persico, G.} } @Article { Klein2018, title = {About the suitability of different numerical methods to reproduce model wind turbine measurements in a wind tunnel with a high blockage ratio}, journal = {Wind Energy Science}, year = {2018}, volume = {3}, pages = {349 - 460}, abstract = {In the present paper, numerical and experimental investigations of a model wind turbine with a diameter of 3.0 m are described. The study has three objectives. The first one is the provision of validation data. The second one is to estimate the influence of the wind tunnel walls by comparing measurements to simulated results with and without wind tunnel walls. The last objective is the comparison and evaluation of methods of high fidelity, namely computational fluid dynamics, and medium fidelity, namely lifting-line free vortex wake. The experiments were carried out in the large wind tunnel of the TU Berlin where a blockage ratio of 40 \% occurs. With the lifting-line free vortex wake code QBlade, the turbine was simulated under far field conditions at the TU Berlin. Unsteady Reynolds-averaged Navier-Stokes simulations of the wind turbine, including wind tunnel walls and under far field conditions, were performed at the University of Stuttgart with the computational fluid dynamics code FLOWer. Comparisons among the experiment, the lifting-line free vortex wake code and the computational fluid dynamics code include on-blade velocity and angle of attack. Comparisons of flow fields are drawn between the experiment and the computational fluid dynamics code. Bending moments are compared among the simulations. A good accordance was achieved for the on-blade velocity and the angle of attack, whereas deviations occur for the flow fields and the bending moments.}, url = {https://doi.org/10.5194/wes-3-439-2018}, DOI = {10.5194/wes-3-439-2018}, author = {Klein, A. C. and Bartholomay, S. and Marten, D. and Lutz, T. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O. and Kr{\"a}mer, E.} } @Article { Bartholomay_2018, title = {Cross-Talk compensation for blade root flap- and edgewise moments on an experimental research wind turbine and comparison to numerical results}, journal = {Proceedings of he ASME Turbo Expo 2018}, year = {2018}, volume = {9 Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy}, number = {GT2018-76977, pp. V009T48A016}, pages = {11}, abstract = {In the current paper a method to correct cross-talk effects for strain-gauge measurements is presented. The method is demonstrated on an experimental horizontal axis wind turbine. The procedure takes cross-moments (flap-wise on edgewise moments and vice versa) as well as axial acceleration into account. The results from the experimental setup are compared to numerical URANS calculations and the medium-fidelity code Qblade for a baseline case and two yawed inflow situations.}, note = {Oslo, Norway, June 11 - 15, 2018}, url = {http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleID=2701583}, editor = {Bartholomay S., Marten D., S{\'a}nchez Martinez M., Alber J., Pechlivanoglou G., Nayeri C. N., Paschereit C. O., Klein A, Lutz Th. and Kr{\"a}mer E.}, series = {ASME Turbo Expo 2018}, organization = {ASME}, ISBN = {978-0-7918-5118-0}, DOI = {10.1115/GT2018-76977}, author = {Bartholomay, S. and Marten, D. and S{\'a}nchez Martinez, M. and Alber, J. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O. and Klein, A. C. and Thorsten, L. and Kr{\"a}mer, E.} } @Article { Saverin_2018, title = {Multilevel Simulation of Aerodynamic Singularity Elements}, journal = {Aerospace Research Central}, year = {2018}, number = {AIAA 2018-0254}, abstract = {The development of a multilevel integration scheme is described. The motivating application is the fast analysis of self-influence of both near and far-wake of a wind turbine. By treating the interaction of the wake with the method of singularity elements, the influence at any point can be expressed as an integral over the domain of the product of a kernel __function and element strength __. In a similar fashion to the well-known fast multipole method, the region of interest is separated into near- and far-field domains with a series of progressive geometric coursening. Element strengths are mapped onto a structured grid of nodes within each domain, or containing box, by using polynomial interpolation. Here barycentric Lagrangian interpolation has been applied with the use of Chebyshev-type node distributions. This method has previously been shown to theoretically reduce the computational expense of the problem from __. The model has been developed to be as general as possible, in order to allow the treatment of a number of different kernel types simultaneously. This expands the applicability to include treatment of singularity elements, wake-boundary interaction and aeroaooustic pressure propagation. Also possible is the extension to surface or volume distributions, making the method applicable to the boundary element method. By comparing the results of the model evaluation achieved with direct evaluation, it is demonstrated that the method works accurately for a number of kernel types including source, dipole and vortex articles methods. The accuracy of the method is shown to be completely controlled by polynomial order P, and an appropriate choice of minimum box sidelength __. The ability of the method to treat vortex particles is demonstrated.}, note = {2018 Wind Energy Symposium Kissimmee, Florida}, url = {https://arc.aiaa.org/doi/10.2514/6.2018-0254}, DOI = {10.2514/6.2018-0254}, author = {Saverin, J. and Marten, D. and Nayeri, C. N. and Pechlivanoglou, G. and Paschereit, C. O.} } @Article { Marten2018, title = {Numerical and Experimental Investigation of Trailing Edge Flap Performance on a Model Wind Turbine Read More: https://arc.aiaa.org/doi/10.2514/6.2018-1246}, journal = {Aerospace Research Central}, year = {2018}, abstract = {A model to assess the performance of active trailing edge flaps on wind turbine blades has recently been integrated with a Liftigng Line Free Vortex Wake code. Successively the codes ability, to accurately predict the effect of trailing edge flaps on the rotor performance and loads in a steady inflow setting was validated with results from tools of ranging fidelity performance in a more complicated setting including yawed inflow was then carried out. For the second benchmark, results between the vortex code, a CFD code and experimental measurements obtained from a model wind turbine were compared. This comparison also highlights the influence of the wind tunnel walls on the experimental results and shows how the free vortex code can predict the experimental results without explicitly including a model o the wind tunnel.}, note = {AIAA SciTech Forum 2018 Wind Energy Symposium, Kissimmee, Florida}, url = {https://arc.aiaa.org/doi/10.2514/6.2018-1246}, DOI = {10.2514/6.2018-1246}, author = {Marten, D. and Bartholomay, S. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O. and Fischer, A. and Lutz, Th.} } @Article { Lennie2018, title = {Vortex shedding and frequency lock in on stand still wind turbines, a baseline experiment}, journal = {Journal of Engineering Gas Turbine Power}, year = {2018}, pages = {15}, abstract = {During the commissioning and stand-still cycles of wind turbines, the rotor is often stopped or even locked leaving the rotor blades at a standstill. When the blades are at a stand still, angles of attack on the blades can be very high and it is therefore possible that they experience vortex induced vibrations. This experiment and analysis helps to explain the different regimes of flow at very high angles of attack, particularly on moderately twisted and tapered blades. A single blade was tested at two different flow velocities at a range of angles of attack with flow tuft visualisation and hotwire measurements of the wake. Hotwire wake measurements were able to show the gradual inception and ending of certain flow regimes. The power spectral densities of these measurements were normalized in terms of Strouhal number based on the projected chord to show that certain wake features have a relatively constant Strouhal number. The shedding frequency appears then to be relatively independent of chord taper and twist. Vortex generators were tested but were found to have little influence in this case. Gurney flaps were found to modify the wake geometry, stall onset angles and in some cases the shedding frequency.}, note = {GTP-17-1616}, url = {http://gasturbinespower.asmedigitalcollection.asme.org/article.aspx?articleid=2677759}, DOI = {10.1115/1.4039818}, author = {Lennie, M. and Selahi-Moghaddam, A. and Holst, D. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.} } @Conference { Perez-Becker_2020, title = {Investigations on the fatigue load reduction potential of advanced control strategies for multi-MW wind turbines using a free vortex wake Model}, year = {2018}, volume = {9}, abstract = {This paper presents the results of a fatigue load evaluation from aeroelastic simulations of a multi-megawatt wind turbine. Both the Blade Element Momentum (BEM) and the Lifting Line Free Vortex Wake (LLFVW) methods were used to compute the aerodynamic forces. The loads in selected turbine components, calculated from NREL's FAST v8 using the aerodynamic solver AeroDyn, are compared to the loads obtained using the LLFVW aerodynamics formulation in QBlade. The DTU 10 MW Reference Wind Turbine is simulated in power production load cases at several wind speeds under idealized conditions. The aerodynamic forces and turbine loads are evaluated in detail, showing very good agreement between both codes. Additionally, the turbine is simulated under realistic conditions according to the current design standards. Fatigue loads derived from load calculations using both codes are compared when the turbine is controlled with a basic pitch and torque controller. It is found that the simulations performed with the BEM method generally predict higher fatigue loading in the turbine components. A higher pitch activity is also predicted with the BEM simulations. The differences are larger for wind speeds around rated wind speed. Furthermore, the fatigue reduction potential of the individual pitch control (IPC) strategy is examined and compared when using the two different codes. The IPC strategy shows a higher load reduction of the out-of-plane blade root bending moments when simulated with the LLFVW method. This is accompanied with higher pitch activity at the actuation frequency of the IPC strategy.}, note = {GT2018-76078, V009T48A008; 11 pages}, url = {https://asmedigitalcollection.asme.org/GT/proceedings-abstract/GT2018/51180/V009T48A008/273154}, organization = {ASME}, ISBN = {978-0-7918-5118-0}, DOI = {10.1115/GT2018-76078}, author = {Perez-Becker, S. and Saverin, J. and Marten, D. and Alber, J. and Pechlivanoglou, G. and Paschereit, C. O.} } @Inproceedings { Holst2018a, title = {Static and dynamic analysis of a NACA 0021 airfoil section at low Reynolds numbers based on experiments and CFD}, year = {2018}, month = {6}, pages = {12}, abstract = {The wind industry needs airfoil data for ranges of Angle of Attack (AoA) much wider than those of aviation applications, since large portions of the blades may operate in stalled conditions for a significant part of their lives. Vertical axis wind turbines (VAWTs) are even more affected by this need, since data sets across the full incidence range of 180 degree are necessary for a correct performance prediction at different tip-speed ratios. However, the relevant technical literature lacks data in deep and post stall regions for nearly every airfoil. Within this context, the present study shows experimental and numerical results for the well-known NACA 0021 airfoil, which is often used for Darrieus VAWT design. Experimental data were obtained through dedicated wind tunnel measurements of a NACA 0021 airfoil with surface pressure taps, which provided further insight into the pressure coefficient distribution across a wide range of AoAs. The measurements were conducted at two different Reynolds umbers (Re=140k and Re=180k): each experiment was performed multiple times to ensure repeatability. Dynamic AoA changes were also investigated at multiple reduced frequencies. Moreover, dedicated unsteady numerical simulations were carried out on the same airfoil shape to reproduce both the static polars of the airfoil and some relevant dynamic AoA variation cycles tested in the experiments. The solved flow fieldwas then exploited both to get further insight into the flow mechanisms highlighted by the wind tunnel tests and to provide correction factors to discard the influence of the experimental apparatus, making experiments representative of open-field behaviour. The present study is then thought to provide the scientific community with high quality, low-Reynolds airfoil data, which may enable in the near future a more effective design of Darrieus VAWTs.}, note = {GT2018-75426}, url = {https://www.asme.org/events/turbo-expo2018}, publisher = {ASME}, series = {Proceedings of ASME Turbo Expo 2018 Turbomachinery Technical Conference and Exposition}, booktitle = {Proceedings of the ASME Turbo Expo 2018}, organization = {ASME}, author = {Holst, D. and Balduzzi, F. and Bianchini, A. and Church, B. and Wegner, F. and Pechlivanoglou, G. and Ferrari, L. and Ferrara, G. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Holst2018b, title = {Experimental analysis of a NACA 0021 airfoil under dynamic angle of attack variation and low Reynolds numbers}, year = {2018}, pages = {12}, abstract = {The wind industry needs reliable and accurate airfoil polars to properly predict wind turbine performance, especially during the initial design phase. Medium- and low-fidelity simulations directly depend on the accuracy of the airfoil data and even more so if e.g. dynamic effects are modeled. This becomes crucial if the blades of a turbine operate under stalled conditions for a significant part of the turbine's lifetime. In addition, the design process of vertical axis wind turbines (VAWTs) needs data across the full range of angles of attack between 0 and 180 deg. Lift, drag and surface pressure distributions of a NACA 0021 airfoil equipped with surface pressure taps were investigated based on time-resolved pressure measurements. The present study discusses full range static polars and several dynamic sinusoidal pitching configurations covering two Reynolds numbers Re = 140k and 180 k, and different incidence ranges: near stall, post stall and deep stall. Various bi-stable flow phenomena are discussed based on high frequency measurements revealing large lift-fluctuations in the post and deep stall regime that exceed the maximum lift of the static polars and are not captured by averaged measurements. Detailed surface pressure distributions are discussed to provide further insight into the flow conditions and pressure development during dynamic motion. The experimental data provided within the present paper is dedicated to the scientific community for calibration and reference purposes, which in the future may lead to higher accuracy in performance predictions during the design process of wind turbines.}, note = {GT2018-76514}, url = {https://www.asme.org/events/turbo-expo2018}, publisher = {ASME}, series = {Proceedings of ASME Turbo Expo 2018 Turbomachinery Technical Conference and Exposition}, booktitle = {Proceedings of the ASME Turbo Expo 2018}, organization = {ASME}, author = {Holst, D. and Church, B. and Wegner, F. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.} } @Article { Reichel_2017, title = {Flashback prevention in lean-premixed hydrogen combustion Vermeidung von Flammenr{\"u}ckschlag in mager vorgemischter Verbrennung von Wasserstoff}, year = {2017}, month = {12}, pages = {108}, abstract = {The focus of this study is the combustion of hydrogen in air as it relates to typical gas turbine engines. Hydrogen-air combustion occurs in the absence of any carbon-based emissions and the only combustion products are water vapor and oxides of nitrogen (NOx). However, due to the very low flammability limit of hydrogen, it can be burned at much lower equivalence ratios than typical hydrocarbon fuels, resulting in excellent low NOx potential. Lean premixed combustion of low reactivity fuels, such as natural gas, is nowadays state of the art in stationary gas turbines. In the long term, it is also a promising approach for aero engines. For lean premixed combustion, with increasing fuel reactivity lean blow out limits are extended but the disposition for flashback, an undesired event of upstream flame propagation, is increased. Therefore, combustor design strategies that are applied for conventional fuels have to be revisited in case of hydrogen, which represents the upper end of the scale of high reactivity fuels. The current thesis aims at developing a combustor design that is capable of safely operating on hydrogen-air mixtures up to stoichiometric conditions while meeting strict emission regulations. To this end, several measures affecting the flashback resistance of a hydrogen-air combustor are investigated. In addition to their effect on flashback resistance, all measures are evaluated with respect to their impact on fuel-air mixing which directly affects NOx emissions. Unlike most previous investigations on hydrogen-air combustion, the current investigations are conducted at partially premixed instead of perfectly premixed conditions. This poses a challenging task with respect to achieving flashback resistance as well as low \textbackslashmathrm\{NO\(_{x\}}\) emissions with limited premixing space and time. Experimental investigation of non-reacting and reacting combustor flow fields of a partially premixed model combustor were conducted using particle image velocimetry in an atmospheric combustor tests rig. Results reveal a strong influence of geometric modifications and fuel momentum on the combustor flow field. Stability maps were recorded that allow for comparison of the operational range of different combustor geometries with respect to flashback and lean blow out. It was shown that already moderate flow rates of a central non-swirling air jet significantly extend the flashback limits, while the lean blow out limits remained unaffected. Moreover, recordings of planar laser-induced fluorescence of the hydroxyl radical (OH-PLIF) within the flame revealed that, the axial location of the upstream flame front, x\(_{f}\), constitutes a telling estimator for flashback resistance. At the investigated conditions, x\(_{f}\) is shifted downstream with increasing equivalence ratio due to the added momentum of the fuel flow. Thereby, the local gain in axial velocity due to fuel momentum supersedes any parallel augmentation in the turbulent flame speed. This has been identified as a driving mechanism affecting the combustor stability limit.Performance and emissions data facilitate the conclusion that the desired flashback-safe operation at very low NOx emissions at ambient pressure and relevant combustor inlet temperatures is feasible. Der Fokus dieser Arbeit liegt auf der experimentellen Untersuchung von Ma{\ss}nahmen zur Gew{\"a}hrleistung der sicheren und schadstoffarmen Verbrennung von Wasserstoff mit Luft in einer Gasturbine. Die Verbrennung von Wasserstoff mit Luft geschieht ohne den Aussto{\ss} jeglicher Kohlenwasserstoffe, sodass sich das Abgas ausschlie{\ss}lich aus Wasserdampf und Stickoxiden zusammensetzt. Der Stickoxidanteil kann dabei auf ein Minimum begrenzt werden da Wasserstoff aufgrund seiner weiten Z{\"u}ndgrenzen extrem mager verbrannt werden kann. Mager vorgemischte Verbrennung, wie sie heutzutage bereits in station{\"a}ren Gasturbinen zum Standard geh{\"o}rt, stellt mittelfristig auch einen vielversprechenden Ansatz f{\"u}r Fluggasturbinen dar. Der Einsatz hochreaktiver Brennstoffe, zum Beispiel wasserstoffreiche Synthesegase oder reiner Wasserstoff, erweitert zwar einerseits deutlich den mageren Betriebsbereich. Andererseits erh{\"o}ht sich auch enorm das Risiko des Auftretens von Flammenr{\"u}ckschlag, welcher zu massiver Besch{\"a}digung von Bauteilen f{\"u}hren kann. Die konventionellen Konzepte der Brennerentwicklung m{\"u}ssen daher f{\"u}r hochreaktive System neu gedacht werden, insbesondere f{\"u}r die Verbrennung von reinem Wasserstoff, der das obere Ende der Skala hochreaktiver Gasturbinentreibstoffe darstellt. Im Rahmen dieser Doktorarbeit wird der Einfluss verschiedener Ma{\ss}nahmen zur Vermeidung von Flammenr{\"u}ckschlag auf das nicht-reagierende und reagierende Str{\"o}mungsfeld experimentell untersucht. Dar{\"u}ber hinaus werden die Auswirkungen dieser {\"A}nderungen des Str{\"o}mungsfeldes auf die Flammenstabilisierung mit Hilfe moderner optischer Messtechnik gezeigt. Die daraus gewonnenen Erkenntnisse verm{\"o}gen die Beobachtungen der gemessenen Stabilit{\"a}tskarten zu erkl{\"a}ren. Durch die Identifikation von Indikatoren f{\"u}r Flammenr{\"u}ckschlag lassen sich au{\ss}erdem Voraussagen f{\"u}r die Stabilit{\"a}t jenseits des experimentell bestimmten Betriebsbereichs treffen. Im Rahmen der Untersuchungen stellte sich insbesondere das St{\"o}rungsfreie Einbringen des hohen Brennstoffimpulses als kritische Ma{\ss}nahme zur Wahrung von Flammenr{\"u}ckschlagsicherheit heraus. Weiterhin wurde gezeigt das verschiedene Ma{\ss}nahmen zur Vermeidung von Flammenr{\"u}ckschlag interagieren und teilweise interferieren. Es konnte jedoch gezeigt werden dass die vorgeschlagene Kombination der Ma{\ss}nahmen in der Brennergeometrie in der Lage ist Flammenr{\"u}ckschlag auf dem gesamten Betriebsbereich der Versuchsanlage zu verhindern und gleichzeitig ambitionierte Emissionsziele zu erf{\"u}llen.}, url = {https://depositonce.tu-berlin.de//handle/11303/7254 http://dx.doi.org/10.14279/depositonce-6530}, institution = {Technische Universit{\"a}t Berlin}, type = {phdthesis}, language = {English}, author = {Reichel, T. G. and Terhaar, S. and Paschereit, C. O.} } @Article { Zanuy2017, title = {Berechnungsformel f{\"u}r den aerodynamischen Widerstand von Containerz{\"u}gen}, journal = {Eisenbahntechnische Rundschau}, year = {2017}, month = {5}, volume = {5}, pages = {78 - 81}, abstract = {In diesem Artikel wird die Entwicklung einer Berechnungsformel f{\"u}r den aerodynamischen Widerstand von Containerz{\"u}gen vorgestellt, in Abh{\"a}ngigkeit von Zugl{\"a}nge, Abstand der auf dem Zug verladenen Container und Zuggeschwindigkeit. Hierzu wurden ein CFD-Modell (computational fluid dynamics model) erstellt und Windkanalversuche ausgewertet. Bei einem mit 100 km/h fahrenden Containerzug der Deutschen Bahn AG ist der Luftwiderstand f{\"u}r 44 \% des Energieverbrauchs der Zugfahrt verantwortlich. Der Abstand zwischen den Containern spielt dabei eine gro{\ss}e Rolle. Anders als bei Hochgeschwindigkeitsz{\"u}gen, die aerodynamisch optimiert sind, und bei Sattelschleppern im Stra{\ss}en-Fernverkehr, bei denen der Energieverbrauch durch aerodynamische Formgebung reduziert werden konnte, fand dieses Thema im G{\"u}terverkehr auf der Schiene bisher wenig Beachtung.}, url = {http://www.eurailpress.de/archiv/fachartikelarchiv/ergebnisliste/artikelansicht.html?tx_it24archiv_list\%5Barticle\%5D=13361\&tx_it24archiv_list\%5Baction\%5D=show\&tx_it24archiv_list\%5Bcontroller\%5D=Article\&cHash=6a63329fb4be304879af99d684076628}, publisher = {ETR}, author = {Zanuy, A. C. and Nayeri, C. N. and P{\'e}rez, O. S.} } @Article { Lennie2017, title = {Development of a partially stochastic unsteady aerodynamics model}, journal = {AIAA SciTech Forum}, year = {2017}, month = {1}, url = {https://arc.aiaa.org/doi/abs/10.2514/6.2017-2002}, publisher = {Aerospace Research Central}, DOI = {10.2514/6.2017-2002}, author = {Lennie, M. and Wendler, J. and Marten, D. and Pechlivanoglou, G. and Paschereit, C. O.} } @Article { Marten2017, title = {Validation and comparison of a newly developed aeroelastic design code for VAWT}, journal = {Aerospace Research Central, AIAA SciTech Forum}, year = {2017}, abstract = {The open source wind turbine simulation code QBlade, based on a Lifting Line Free Vortex Wake formulation to evaluate the unsteady aerodynamics, recently integrated the PROJECTCHRONO FEA library that, by using Euler-Bernoulli beams in a corotational formulation, solves for the structural dynamics to achieve an aeroelastic coupling. To validate the newly implemented structural model its performance is compared to literature data and two other finite element computer codes. The comparison is based on a modal analysis and aeroelastic simulations of the SNL 34m VAWT testbed, for which the aerodynamic and structural properties are well known. The structural loads are obtained from IE C 61400-1 design load cases. In one of the calculated load cases an aeroelastic instability could be observed which confirms similar observations that have previously been reported in the literature.}, note = {35th Wind Energy Symposium 9 - 13 January 2017 Grapevine, Texas}, url = {http://dx.doi.org/10.2514/MWES17}, DOI = {10.2514/6.2017-0452}, author = {Marten, D. and Lennie, M. and Pechlivanoglou, G. and Paschereit, C. O. and Dy, N. V. and Paraschivoiu, I. and Saeed, F.} } @Inbook { Menzel2017, title = {Visualisierungswindkanal (ViWiKa) f{\"u}r Messe, Forschung und Lehre auf Basis von myRIO-1900}, year = {2017}, pages = {430 - 434}, web_url = {http://www.etz.de/files/10_02_menzel-holst-fischer.pdf}, editor = {Rahman J., Heinze R.}, publisher = {VDE Verlag}, chapter = {Forschung und Lehre in Virtuelle Instrumente in der Praxis 2017}, ISBN = {978-3-800-4441-1}, author = {Menzel, C. and Holst, D. and Fischer, J. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Alber2017, title = {Parametric investigation of Gurney Flaps for the use on wind turbine blades}, year = {2017}, month = {8}, day = {17}, pages = {10}, abstract = {This paper presents a strategy to model the aerodynamic Gurney flap effect on two-dimensional airfoils and subsequently on the rotor blade performance of horizontal axis wind turbines.The first part consists of the parametric investigation of 26 airfoil polar data-sets, derived from different, but comparable, wind tunnel experiments. They are evaluated and processed in terms of the lift and drag increase caused by Gurney flaps in comparison to each Baseline configuration. Consequently, a model is developed, transforming Baseline- into Gurney flap polar data for varying flap-heights. The results of the emerging Gurney Flap Polar Calculator are validated against the experimental lift and drag curves.In the second part, the blade design of the NREL 5 MW Reference Turbine is modified by implementing polar data-sets of varying Gurney flap-heights, which are imported into the rotor simulation software QBlade. Thereupon, blade optimization strategies are examined regarding the two main Gurney flap applications on rotor blades: the retrofit and the design solution. The optimized retrofit solution on existing blades indicates power performance improvements, albeit at the expense of increasing structural loads. The optimized design solution on to-be-constructed blades, on the other hand, suggests chord-length reductions, while keeping the performance characteristics on a similar or even enhanced level.It is concluded that aerodynamic improvements are achieved by relatively small Gurney flap-heights, which are applied at specific blade positions.}, keywords = {Blades, Wind turbines, Design, Rotors, Airfoils, Drag (Fluid dynamics), Chords (Trusses), Computer software, Horizontal axis wind turbines, Optimization, Performance characterization, Simulation, Stress, Turbines, Wind tunnels}, url = {https://doi.org/10.1115/GT2017-64475}, booktitle = {ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition}, ISBN = {978-0-7918-5096-1}, author = {Alber, J. and Pechlivanoglou, G. and Paschereit, C. O. and Twele, J. and Weinzierl, G.} } @Inproceedings { Holst2017, title = {Experimental Analysis of a NACA 0021 Airfoil Section Through 180-Degree Angle of Attack at Low Reynolds Numbers for Use in Wind Turbine Analysis}, year = {2017}, month = {6}, day = {30}, volume = {9}, pages = {12}, abstract = {Wind turbine industry has a special need for accurate post stall airfoil data. While literature often covers incidence ranges [−10deg,+25deg] smaller machines experience a range of up to 90 deg for horizontal axis and up to 360 deg for vertical axis wind turbines (VAWTs). The post stall data of airfoils is crucial to improve the prediction of the start-up behavior as well as the performance at low tip speed ratios. The present paper analyzes and discusses the performance of the symmetrical NACA 0021 airfoil at three Reynolds numbers (Re = 100k, 140k, and 180k) through 180 deg incidence. The typical problem of blockage within a wind tunnel was avoided using an open test section. The experiments were conducted in terms of surface pressure distribution over the airfoil for a tripped and a baseline configuration. The pressure was used to gain lift, pressure drag, moment data. Further investigations with positive and negative pitching revealed a second hysteresis loop in the deep post stall region resulting in a difference of 0.2 in moment coefficient and 0.5 in lift.}, url = {http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2650571}, publisher = {ASME}, series = {Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy}, booktitle = {ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition}, organization = {ASME}, event_place = {Charlotte, North Carolina, USA}, event_name = {ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition}, event_date = {26 - 30 Juni 2017}, language = {English}, ISBN = {ISBN: 978-0-7918-5096-1}, DOI = {10.1115/GT2017-63643}, author = {Holst, D. and Church, B. and Pechlivanoglou, G. and T{\"u}z {\"U}ner, E. and Saverin, J. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Holst2017a, title = {Comparison of Experimental and Numerically Predicted Three-Dimensional Wake Behaviour of a Vertical Axis Wind Turbine}, year = {2017}, month = {6}, volume = {9}, abstract = {The evolution of the wake of a wind turbine contributes significantly to its operation and performance, as well as to those of machines installed in the vicinity. The inherent unsteady and three-dimensional aerodynamics of Vertical Axis Wind Turbines (VAWT) have hitherto limited the research on wake evolution. In this paper the wakes of both a troposkien and a H-type VAWT rotor are investigated by comparing experiments and calculations. Experiments were carried out in the large-scale wind tunnel of the Politecnico di Milano, where unsteady velocity measurements in the wake were performed by means of hot wire anemometry. The geometry of the rotors was reconstructed in the open-source wind-turbine software QBlade, developed at the TU Berlin. The aerodynamic model makes use of a lifting line free-vortex wake (LLFVW) formulation, including an adapted Beddoes-Leishman unsteady aerodynamic model; airfoil polars are introduced to assign sectional lift and drag coefficients. A wake sensitivity analysis was carried out to maximize the reliability of wake predictions. The calculations are shown to reproduce several wake features observed in the experiments, including blade-tip vortex, dominant and submissive vortical structures, and periodic unsteadiness caused by sectional dynamic stall. The experimental assessment of the simulations illustrates that the LLFVW model is capable of predicting the unsteady wake development with very limited computational cost, thus making the model ideal for the design and optimization of VAWTs.}, url = {http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2650574}, publisher = {ASME}, series = {Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy}, booktitle = {ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition}, organization = {ASME}, event_place = {Charlotte, North Carolina, USA}, event_name = {ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition}, event_date = {26 - 30 Juni 2017}, language = {English}, ISBN = {ISBN: 978-0-7918-5096-1}, DOI = {10.1115/GT2017-64004}, author = {Saverin, J. and Marten, D. and Holst, D. and Pechlivanloglou, G. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Holst2017b, title = {Vortex Shedding and Frequency Lock in on Stand Still Wind Turbines: A Baseline Experiment}, year = {2017}, month = {6}, volume = {9}, pages = {17}, abstract = {During the commissioning and stand-still cycles of wind turbines, the rotor is often stopped or even locked leaving the rotor blades at a standstill. When the blades are at a stand still, angles of attack on the blades can be very high and it is therefore possible that they experience vortex induced vibrations. This experiment and analysis helps to explain the different regimes of flow at very high angles of attack, particularly on moderately twisted and tapered blades. A single blade was tested at two different flow velocities at a range of angles of attack with flow tuft visualisation and hotwire measurements of the wake. Hotwire wake measurements were able to show the gradual inception and ending of certain flow regimes. The power spectral densities of these measurements were normalized in terms of Strouhal number based on the projected chord to show that certain wake features have a relatively constant Strouhal number. The shedding frequency appears then to be relatively independent of chord taper and twist. Vortex generators were tested but were found to have little influence in this case. Gurney flaps were found to modify the wake geometry, stall onset angles and in some cases the shedding frequency.}, url = {http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2650572}, publisher = {ASME}, series = {Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy}, booktitle = {ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition}, organization = {ASME}, event_place = {Charlotte, North Carolina, USA}, event_name = {ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition}, event_date = {26 - 30 Juni 2017}, language = {English}, DOI = {0.1115/GT2017-63653}, author = {Lennie, M. and Selahi-Moghaddam, A. and Holst, D. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.} } @Article { Grewe2016, title = {Assessing the climate impact of the AHEAD multi-fuel blended wing body}, journal = {Meteorologische Zeitschrift}, year = {2016}, month = {10}, volume = {139}, pages = {1 - 15}, abstract = {Air traffic is important to our society and guarantees mobility especially for long distances. Air traffic is also contributing to climate warming via emissions of CO2 and various non-CO2 effects, such as contrail-cirrus or increase in ozone concentrations. Here we investigate the climate impact of a future aircraft design, a multi fuel blended wing body (MF-BWB), conceptually designed within the EU-project AHEAD. We re-calculate the parameters for the contrail formation criterion, since this aircraft has very different characteristics compared to conventional technologies and show that contrail formation potentially already occurs at lower altitudes than for conventional aircraft. The geometry of the contrails, however, is similar to conventional aircraft, as detailed LES simulations show. The global contrail-cirrus coverage and related radiative forcing is investigated with a climate model including a contrail-cirrus parameterisation and shows an increase in contrail-cirrus radiative forcing compared to conventional technologies, if the number of emitted particles is equal to conventional technologies. However, there are strong indications that the AHEAD engines would have a substantial reduction in the emission of soot particles and there are strong indications that this leads to a substantial reduction in the contrail-cirrus radiative forcing. An overall climate impact assessment with a climate-chemistry response model shows that the climate impact is likely to be reduced by 20 \% to 25 \% compared to a future aircraft with conventional technologies. We further tested the sensitivity of this result with respect to different future scenarios for the use of bio fuels, improvements of the fuel efficiency for conventional aircraft and the impact of the number of emitted soot particles on the radiative forcing. Only the latter has the potential to significantly impact our findings and needs further investigation. Our findings show that the development of new and climate compatible aircraft designs requires the inclusion of climate impact assessments already at an early stage, i.e. pre-design level.}, note = {Online ver{\"o}ffentlicht: Oct 14, 2016 Manuskript akzeptiert: Jun 22, 2016 Manuskript-Revision erhalten: Jun 16, 2016 Manuskript-Revision angefordert: Jan 2, 2014 Manuskript erhalten: Nov 18, 2015}, keywords = {AHEAD project • Multi fuel blended wing body • contrails • climate impact • air traffic}, url = {http://www.schweizerbart.de/papers/metz/detail/prepub/87038/Assessing_the_climate_impact_of_the_AHEAD_multi_fuel_blended_wing_body}, publisher = {Schweizerbart Science Publishers}, address = {Stuttgart, Germany}, howpublished = {online Oct 14, 2016}, DOI = {10.1127/metz/2016/0758}, author = {Grewe, V. and Bock, L. and Burkhardt, U. and Dahlmann, K. and Gierens, K. and H{\"u}ttenhofer, L. and Unterstrasser, S. and Rao, A. G. and Bhat, A. and Yin, F. and Reichel, T. G. and Paschereit, C. O. and Leshayahou, Y.} } @Article { Lennie2016, title = {Modern methods for investigating the stability of a pitching floating platform wind turbine}, journal = {Journal of Physics}, year = {2016}, month = {10}, volume = {Conference Series, 753}, url = {http://iopscience.iop.org/article/10.1088/1742-6596/753/8/082012/meta}, publisher = {IOPscience}, DOI = {10.1088/1742-6596/753/8/082012}, author = {Lennie, M. and Marten, D. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.} } @Article { Sieber_2016, title = {Advanced Identification of coherent structures in swirl-stabilized combustors}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2016}, month = {9}, url = {http://gasturbinespower.asmedigitalcollection.asme.org/article.aspx?articleid=2539421}, DOI = {10.1115/1.4034261}, author = {Sieber, M. and Paschereit, C. O. and Oberleithner, K.} } @Article { Sieber2016_, title = {Lagrangian coherent structures in the flow field of a fluidic oscillator}, journal = {Physical Review Fluids}, year = {2016}, month = {9}, volume = {1}, url = {http://dx.doi.org/10.1103/APS.DFD.2015.GFM.V0015}, DOI = {10.1103/PhysRevFluids.1.050509}, author = {Sieber, M. and Ostermann, F. and Woszidlo, R. and Oberleithner, K. and Paschereit, C. O.} } @Article { Rukes_2016, title = {Methods for the extraction and analysis of the global mode in swirling jets undergoing vortex breakdown}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2016}, month = {9}, volume = {139}, url = {http://gasturbinespower.asmedigitalcollection.asme.org/article.aspx?articleid=2541041}, DOI = {10.1115/gt2016-56588}, author = {Rukes, L. and Sieber, M. and Paschereit, C. O. and Oberleithner, K.} } @Article { Rukes2016_, title = {The impact of heating the breakdown bubble on the global mode of a swirling jet: Experiments and linear stability analysis}, journal = {Physics of Fluids}, year = {2016}, month = {9}, volume = {28}, url = {http://scitation.aip.org/content/aip/journal/pof2/28/10/10.1063/1.4963274}, author = {Rukes, L. and Sieber, M. and Paschereit, C. O. and Oberleithner, K.} } @Article { Reichel2016, title = {Shockless Explosion Combustion: Experimental Investigation of a New Approximate Constant Volume Combustion Process}, journal = {ASME Journal of Engineering for Gas Turbines and Power}, year = {2016}, month = {6}, volume = {139}, number = {2}, abstract = {Approximate constant volume combustion (aCVC) is a promising way to achieve a step change in the efficiency of gas turbines. This work investigates a recently proposed approach to implement aCVC in a gas turbine combustion system: shockless explosion combustion (SEC). The new concept overcomes several disadvantages such as sharp pressure transitions, entropy generation due to shock waves, and exergy losses due to kinetic energy which are associated with other aCVC approaches such as pulsed detonation combustion. The combustion is controlled via the fuel/air mixture distribution which is adjusted such that the entire fuel/air volume undergoes a spatially quasi-homogeneous auto-ignition. Accordingly, no shock waves occur and the losses associated with a detonation wave are not present in the proposed system. Instead, a smooth pressure rise is created due to the heat release of the homogeneous combustion. An atmospheric combustion test rig is designed to investigate the auto-ignition behavior of relevant fuels under intermittent operation, currently up to a frequency of 2 Hz. Application of OH*- and dynamic pressure sensors allows for a spatially and time-resolved detection of ignition delay times and locations. Dimethyl ether (DME) is used as fuel since it exhibits reliable auto-ignition already at 920 K mixture temperature and ambient pressure. First, a model-based control algorithm is used to demonstrate that the fuel valve can produce arbitrary fuel profiles in the combustion tube. Next, the control algorithm is used to achieve the desired fuel stratification, resulting in a significant reduction in spatial variance of the auto-ignition delay times. This proves that the control approach is a useful tool for increasing the homogeneity of the auto-ignition.}, note = {Journal of Engineering for Gas Turbines and Power Publication Title History February, 2017 | Volume 139 | Issue 2}, url = {http://gasturbinespower.asmedigitalcollection.asme.org/article.aspx?articleid=2537131\&resultClick=1}, DOI = {10.1115/1.4034214}, author = {Reichel, T. G. and Sch{\"a}pel, J. S. and Berndt, P. and King, R. and Klein, R. and Paschereit, C. O. and Christian, O.} } @Article { Wassmer2016, title = {Measurement and Modeling of the Generation and the Transport of Entropy Waves in a Model Gas Turbine Combustor}, year = {2016}, month = {5}, day = {30}, pages = {GTRE-044}, url = {http://www.tum-ias.de/thermoacoustics2016/focus-impact.html}, author = {Wassmer, D. and Schuermans, B. and Paschereit, C. O. and Moeck, J. P.} } @Article { Strangfeld2016, title = {Airfoil in a high amplitude oscillating stream}, journal = {Journal of Fluid Mechanics}, year = {2016}, month = {4}, volume = {793}, pages = {79--108}, url = {http://journals.cambridge.org/article_S0022112016001269}, ISSN = {1469-7645}, DOI = {10.1017/jfm.2016.126}, author = {Strangfeld, C. and M{\"u}ller-Vahl, H. and Nayeri, C. N. and Paschereit, C. O. and Greenblatt, D.} } @Article { Schuele2016, title = {Experimental and Numerical Investigation of an Axial Rotary Blood Pump}, journal = {Artificial Organs}, year = {2016}, month = {4}, editor = {Paul S. Malchesky}, organization = {International Federation for Artificial Organs}, ISSN = {1525-1594}, DOI = {10.1111/aor.12725}, author = {Sch{\"u}le, C. Y. and Thamsen, B. and Bl{\"u}mel, B. and Lommel, M. and Karakaya, T. and Paschereit, C. O. and Affeld, K. and Kertzscher, U.} } @Article { Lennie_2016, title = {The unsteady aerodynamic response of an airfoil with microtabs and it's implications for aerodynamic damping}, journal = {AIAA SciTech Forum}, year = {2016}, month = {1}, volume = {Conference Series}, url = {http://dx.doi.org/10.2514/MWES16}, publisher = {Aerospace Research Central}, DOI = {10.2514/6.2016-1006}, author = {Lennie, M. and Bach, A. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.} } @Article { Wendler_2016, title = {An Unsteady Aerodynamics Model for Lifting Line Free Vortex Wake Simulations of HAWT and VAWT in QBlade}, journal = {Proceedings of ASME Turbo Expo 2016, June 13-17, 2016, Seoul, South Korea}, year = {2016}, volume = {9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy}, pages = {11 Pages}, abstract = {This paper describes the introduction of an unsteady aerodynamics model applicable for horizontal and vertical axis wind turbines (HAWT/VAWT) into the advanced blade design and simulation code QBlade, developed at the HFI of the TU Berlin. The software contains a module based on lifting line theory including a free vortex wake algorithm (LLFVW) which has recently been coupled to the structural solver of FAST to allow for time-resolved aeroelastic simulations of large, flexible wind turbine blades. The aerodynamic model yields an accuracy improvement with respect to Blade Element Momentum (BEM) theory and a more practical approach compared to higher fidelity methods such as Computational Fluid Dynamics (CFD) which are too computationally demanding for load case calculations. To capture the dynamics of flow separation, a semi-empirical method based on the Beddoes-Leishman model now extends the simple table lookups of static polar data by predicting the unsteady lift and drag coefficients from steady data and the current state of motion. The model modifications for wind turbines and the coupling to QBlade's vortex method are described. A 2D validation of the implementation is presented in this paper to demonstrate the capability and reliability of the resulting simulation scheme. The applicability of the model is shown for exemplary HAWT and VAWT test cases. The modelling of the dynamic stall vortex, the empiric model constants as well as the influence of the dynamic coefficients on performance predictions are investigated.}, note = {Proceedings of ASME Turbo Expo 2016, June 13-17, 2016, Seoul, South Korea}, url = {http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2555667}, DOI = {10.1115/GT2016-57184}, author = {Wendler, J. and Marten, D. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.} } @Article { Marten2016, title = {Effects of Airfoil's Polar Data in the Stall Region on the Estimation of Darrieus Wind Turbine Performance}, journal = {ASME}, year = {2016}, volume = {139}, number = {2}, pages = {9}, abstract = {Interest in vertical-axis wind turbines (VAWTs) is experiencing a renaissance after most major research projects came to a standstill in the mid 1990s, in favor of conventional horizontal-axis turbines (HAWTs). Nowadays, the inherent advantages of the VAWT concept, especially in the Darrieus configuration, may outweigh their disadvantages in specific applications, like the urban context or floating platforms. To enable these concepts further, efficient, accurate, and robust aerodynamic prediction tools and design guidelines are needed for VAWTs, for which low-order simulation methods have not reached yet a maturity comparable to that of the blade element momentum theory for HAWTs' applications. The two computationally efficient methods that are presently capable of capturing the unsteady aerodynamics of Darrieus turbines are the double multiple streamtubes (DMS) theory, based on momentum balances, and the lifting line theory (LLT) coupled to a free vortex wake model. Both methods make use of tabulated lift and drag coefficients to compute the blade forces. Since the incidence angles range experienced by a VAWT blade is much wider than that of a HAWT blade, the accuracy of polars in describing the stall region and the transition toward the ''thin plate like'' behavior has a large effect on simulation results. This paper will demonstrate the importance of stall and poststall data handling in the performance estimation of Darrieus VAWTs. Using validated CFD simulations as a baseline, comparisons are provided for a blade in VAWT-like motion based on a DMS and a LLT code employing three sets of poststall data obtained from a wind tunnel campaign, XFoil predictions extrapolated with the Viterna-Corrigan model and a combination of them. The polar extrapolation influence on quasi-steady operating conditions is shown and azimuthal variations of thrust and torque are compared for exemplary tip-speed ratios (TSRs). In addition, the major relevance of a proper dynamic stall model into both the simulation methods is highlighted and discussed.}, note = {Paper No: GTP-16-1286}, url = {http://gasturbinespower.asmedigitalcollection.asme.org/article.aspx?articleid=2541658\&resultClick=3}, DOI = {10.1115/1.4034326}, author = {Marten, D. and Bianchini, S. and Pechlivanoglou, G. and Balduzzi, F. and Nayeri, C. N. and Ferrara, G. and Paschereit, C. O. and Ferrari, L.} } @Article { Stathopoulos2016b, title = {Emissions of a wet premixed flame of natural gas and a mixture with hydrogen at high pressure}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2016}, volume = {139}, number = {4}, pages = {8}, url = {http://gasturbinespower.asmedigitalcollection.asme.org/issue.aspx?journalid=120\&issueid=935804}, publisher = {ASME}, author = {Stathopoulos, P. and Kuhn, P. and Wendler, J. and Tanneberger, T. and Terhaar, S. and Paschereit, C. O. and Schmalhofer, C. and Griebel, P. and Aigner, M.} } @Article { Reichel2016, title = {Interaction Mechanisms of Fuel Momentum with Flashback Limits in Lean-Premixed Combustion of Hydrogen}, journal = {International Journal of Hydrogen Energy}, year = {2016}, volume = {41}, abstract = {The impact of fuel momentum on the combustor flow field is studied experimentally in a swirl-stabilized, technically premixed hydrogen flame. The volumetric heating value of hydrogen is about 3.5 times lower compared to natural gas, which leads to significantly higher volumetric fuel flow rates at the same power level. This additional fuel momentum significantly alters the combustor flow field. Therefore, the fuel momentum also affects the combustor stability limits. Previous studies were mostly conducted at perfectly premixed conditions, where the fuel momentum does not alter the combustor flow field. In the current study, non-reacting and reacting combustor flow fields of a technically premixed model combustor injecting fuel in axial direction are recorded. Results reveal a strong impact of fuel momentum on axial velocity distribution at the mixing tube outlet and, thus, on the stability limits. Additionally, OH-PLIF recordings for different flow rates, air preheat temperatures, and equivalence ratios show that the axial location of the upstream flame front, xf, poses a telling estimator for flashback resistance. No flashback was observed when the upstream flame front was located downstream of the mixing tube. However, the flame tip always located upstream of the mixing tube outlet prior to flashback. A high value of xf was, thus, identified as a sufficient condition for flashback resistance. At the investigated conditions, xf is shifted downstream with increasing equivalence ratio due to the added momentum of the fuel flow, thereby superseding any parallel augmentation in the turbulent flame speed. This has been identified as the driving mechanism affecting the combustor stability limit.}, url = {http://www.sciencedirect.com/science?_ob=ArticleListURL\&_method=list\&_ArticleListID=-1122493821\&_sort=r\&_st=13\&view=c\&md5=7c21464c1e012c6b3e2a6ac4e8b3c8e4\&searchtype=a}, ISSN = {03603199}, DOI = {10.1016/j.ijhydene.2016.11.018}, author = {Reichel, T. G. and Paschereit, C. O. and Christian, O.} } @Article { Schäpel2016, title = {Online Optimization Applied to a Shockless Explosion Combustor}, journal = {processes}, year = {2016}, volume = {4(4)}, abstract = {Changing the combustion process of a gas turbine from a constant-pressure to a pressure-increasing approximate constant-volume combustion (aCVC) is one of the most promising ways to increase the efficiency of turbines in the future. In this paper, a newly proposed method to achieve such an aCVC is considered. The so-called shockless explosion combustion (SEC) uses auto-ignition and a fuel stratification to achieve a spatially homogeneous ignition. The homogeneity of the ignition can be adjusted by the mixing of fuel and air. A proper filling profile, however, also depends on changing parameters, such as temperature, that cannot be measured in detail due to the harsh conditions inside the combustion tube. Therefore, a closed-loop control is required to obtain an adequate injection profile and to reject such unknown disturbances. For this, an optimization problem is set up and a novel formulation of a discrete extremum seeking controller is presented. By approximating the cost function with a parabola, the first derivative and a Hessian matrix are estimated, allowing the controller to use Newton steps to converge to the optimal control trajectory. The controller is applied to an atmospheric test rig, where the auto-ignition process can be investigated for single ignitions. In the set-up, dimethyl ether is injected into a preheated air stream using a controlled proportional valve. Optical measurements are used to evaluate the auto-ignition process and to show that using the extremum seeking control approach, the homogeneity of the ignition process can be increased significantly.}, keywords = {shockless explosion combustion; constant volume combustion; extremum seeking control}, url = {http://www.sciencedirect.com/science?_ob=ArticleListURL\&_method=list\&_ArticleListID=-1122493821\&_sort=r\&_st=13\&view=c\&md5=7c21464c1e012c6b3e2a6ac4e8b3c8e4\&searchtype=a}, ISSN = {03603199}, DOI = {10.3390/pr4040048}, author = {Sch{\"a}pel, J. S. and Reichel, T. G. and Klein, R. and Paschereit, C. O. and Christian, O. and King, R.} } @Article { Holst_2016, title = {Potential of Retrofit Passive Flow Control for Small Horizontal Axis Wind Turbines}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2016}, volume = {139}, number = {6}, pages = {032604-1 - 032604-8}, abstract = {The present paper analyzes the effect of passive flow control (PFC) with respect to the retrofitting on small horizontal axis wind turbines (sHAWTs). We conducted extensive wind tunnel studies on a high performance low Reynolds airfoil using different PFC elements, i.e., vortex generators (VGs) and Gurney flaps (GF). qblade, an open source blade element momentum (BEM) code, is used to study the retrofitting potential of a simulated small wind turbine. The turbine design is presented and discussed. The simulations include the data and polars gained from the experiments and give further insight into the effects of PFC on sHAWTs. Therefore, several different blades were simulated using several variations of VG positions. This paper discusses their influence on the turbine performance. The authors especially focus on the startup performance as well as achieving increased power output at lower wind speeds. The vortex generators reduce the risk of laminar separation and enhance the lift in some configurations by more than 40 \% at low Reynolds numbers.}, url = {http://gasturbinespower.asmedigitalcollection.asme.org/article.aspx?articleid=2547692}, ISSN = {0742-4795}, DOI = {10.1115/1.4034543}, author = {Holst, D. and Pechlivanoglou, G. and Wegner, F. and Nayeri, C. N. and Paschereit, C. O.} } @Article { Gray_2016, title = {Thermodynamic Evaluation of Pulse Detonation Combustion for Gas Turbine Power Cycles}, journal = {Proceedings of ASME Turbomachinery Technical Conference \& Exposition. Seoul, South Korea, June 13-17, 2016}, year = {2016}, volume = {Volume 4B: Combustion, Fuels and Emissions}, number = {Paper No. GT2016-57813, pp. V04BT04A044}, pages = {9}, abstract = {Constant-volume (pressure-gain) combustion cycles show much promise for further increasing the efficiency of modern gas turbines, which in the last decades have begun to reach the boundaries of modern technology in terms of pressure and temperature, as well as the ever more stringent demands on reducing exhaust gas emissions. The thermodynamic model of the gas turbine consists of a compressor with a polytropic efficiency of 90\%, a combustor modeled as either a pulse detonation combustor (PDC) or as an isobaric homogeneous reactor, and a turbine, the efficiency of which is calculated using suitable turbine operational maps. A simulation is conducted using the one-dimensional reacting Euler equations to obtain the unsteady PDC outlet parameters for use as turbine inlet conditions. The efficiencies for the Fickett-Jacobs and Joule cycles are then compared. The Fickett-Jacobs cycle shows promise at relatively low compressor pressure ratios, whereas the importance of the harvesting of exhaust gas kinetic energy for the cycle performance is highlighted.}, note = {Proceedings of ASME Turbomachinery Technical Conference \& Exposition. Seoul, South Korea, June 13 - 17, 2016}, url = {http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2555111}, ISBN = {978-0-7918-4976-7}, DOI = {10.1115/gt2016-57813}, author = {Gray, J. and Vinkeloe, J. and Moeck, J. P. and Paschereit, C. O. and Stathopoulos, P. and Berndt, P. and Klein, R.} } @Inbook { Holst2016c, title = {Entwicklung eines aerodynamischen Pr{\"u}fstands zur Fl{\"u}gelprofiluntersuchung von Kleinwindkraftanlagen unter dynamischen Winkel{\"a}nderungen auf Basis eines cRiO-9068}, year = {2016}, pages = {54 - 57}, url = {http://sine.ni.com/cs/app/doc/p/id/cs-17418}, editor = {Rahman J., Heinze R.,}, publisher = {VDE Verlag}, edition = {Begleitband zum 21. VIP-Kongress}, chapter = {Mess-, Pr{\"u}f- und Regelungstechnik in Virtuelle Instrumente in der Praxis 2016}, ISBN = {978-3-8007-4441-1}, author = {Holst, D. and Thommes, K. and Sch{\"o}nlau, M. and Nayeri, C. N. and Paschereit, C. O.} } @Inbook { Kabiraj2016, title = {Recurrence Plots and Their Quantifications: Expanding Horizons: Proceedings of the 6th International Symposium on Recurrence Plots, Grenoble, France, 17-19 June 2015}, year = {2016}, pages = {321-339}, editor = {Webber Jr., L. C. and Ioana, C. and Marwan, N.}, publisher = {Springer International Publishing}, chapter = {Recurrence Plots for the Analysis of Combustion Dynamics}, ISBN = {978-3-319-29922-8}, DOI = {10.1007/978-3-319-29922-8_17}, author = {Kabiraj, L. and Saurabh, A. and Nawroth, H. and Paschereit, C. O. and Sujith, R. I. and Karimi, N.} } @Conference { Marten2016a, title = {Nonlinear Lifting Line Theory Applied To Vertical Axis Wind Turbines: Development of a Practical Design Tool}, year = {2016}, pages = {8}, abstract = {Recently a new interest in vertical axis wind turbine (VAWT) technology is fueled by research on floating support structures for large scale offshore wind energy application. For the application on floating structures at multi megawatt size, the VAWT concept may offer distinct advantages over the conventional horizontal axis wind turbine (HAWT) design. As an example VAWT turbines are better suited for upscaling and, at multi megawatt size, the problem of periodic fatigue cycles reduces significantly due to a very low rotational speed. Additionally, the possibility to store the transmission and electricity generation system at the bottom, compared to the tower top as in a HAWT, can lead to a considerable reduction of material logistics costs. However, as most VAWT research stalled in the mid 90's, no established and sophisticated tools to investigate this concept further exist today. Due to the complex interaction between unsteady aerodynamics and movement of the floating structure fully coupled simulation tools, modelling both aero- and structural dynamics are needed. A nonlinear Lifting Line Free Vortex Wake code was recently integrated into the open source wind turbine simulation suite QBlade. This paper describes some of the necessary adaptions of the algorithm, which differentiates it from the usual application in HAWT simulations. A focus is set on achieving a high robustness and computational efficiency. A short validation study compares simulation results with those of a U-RANS and a Double Multiple Streamtube (DMS) simulation.}, url = {http://isromac-isimet.univ-lille1.fr/index.php?rubrique=abstract\&num=24}, publisher = {ISROMAC 16}, DOI = {10.13140/RG.2.1.3116.5849}, author = {Marten, D. and Lennie, M. and Nayeri, C. N. and Paschereit, C. O.} } @Incollection { Nayeri2016b, title = {The Influence of Wind Tunnel Grid Turbulence on Aerodynamic Coefficients of Trains}, year = {2016}, volume = {79}, pages = {133-141}, editor = {Dillmann, A. and Orellano, A.}, publisher = {Springer International Publishing}, series = {Lecture Notes in Applied and Computational Mechanics}, booktitle = {The Aerodynamics of Heavy Vehicles III}, language = {English}, ISBN = {978-3-319-20121-4}, DOI = {10.1007/978-3-319-20122-1_8}, author = {Nayeri, C. N. and Strangfeld, C. and Zellmann, C. and Schober, M. and Tietze, A. and Paschereit, C. O.} } @Incollection { Nayeri2016, title = {Towing Tank Experiments for Bluff Body Aerodynamics}, year = {2016}, volume = {79}, editor = {A. Dillmann, A. Orellano}, publisher = {Springer International Publishing}, series = {Lecture Notes in Applied and Computational Mechanics}, booktitle = {The Aerodynamics of Heavy Vehicles III: Trucks, Buses and Trains}, ISBN = {978-3-319-20121-4 (Print) 978-3-319-20122-1 (Online)}, ISSN = {1613-7736}, DOI = {10.1007/978-3-319-20122-1}, author = {Nayeri, C. N. and Glas, J. and Paschereit, C. O.} } @Inproceedings { Sieber2016, title = {Advanced identification of coherent structures in swirl-stabilized combustors}, year = {2016}, number = {ASME Paper GT2016-56591}, booktitle = {Proceedings of ASME Turbo Expo 2016, June 13-17, 2016, Seoul, South Korea}, DOI = {10.1115/GT2016-56591}, author = {Sieber, M. and Paschereit, C. O. and Oberleithner, K.} } @Inproceedings { Wassmer2016, title = {An Acoustic Time-of-Flight Approach for Unsteady Temperature Measurements: Characterization of Entropy Waves in a Model Gas Turbine Combustor}, year = {2016}, number = {ASME Paper GT2016-56571}, booktitle = {Proceedings of ASME Turbo Expo 2016, June 13-17, 2016, Seoul, South Korea}, DOI = {10.1115/GT2016-56571}, author = {Wassmer, D. and Schuermans, B. and Paschereit, C. O. and Moeck, J. P.} } @Inproceedings { Kuhn_2016, title = {Control of the precessing vortex core by open and closed-loop forcing in the jet core}, year = {2016}, volume = {Volume 4B: Combustion, Fuels and Emissions}, pages = {13}, abstract = {The precessing vortex core (PVC) is the dominant coherent structure of swirling jets, which are commonly applied in gas turbine combustion. It stems from a global hydrodynamic instability that is caused by internal feedback mechanisms in the jet core. In this work, we apply open and closed-loop forcing in a generic non-reacting jet to control this mechanism and the PVC. Control is exerted by two oppositely facing, counter-phased zero-net mass flux jets, which are introduced radially into the flow through a thin lance positioned on the jet center axis. By using this type of forcing, the instability mode m = 1, corresponding to the PVC, can either be excited or damped. This markedly affects the PVC oscillation frequency and amplitude. The passive influence of the actuation lance on the mean flow field properties and the coherent flow dynamics is studied first without forcing. PIV and hot-wire measurements reveal an effect on the mean flow, but no qualitative changes of the PVC dynamics. Lock-in experiments are conducted, in which the synchronization behavior of the PVC with the forcing is determined. Here, two different cases are considered. First, actuation is applied at different streamwise positions in order to identify the region of highest receptivity towards external forcing. This region of lowest lock-in amplitude is shown to coincide with the location of the wavemaker, shortly upstream of the vortex breakdown bubble. Second, the lock-in behavior at a fixed axial position and various forcing frequencies ff is studied. A linear correlation between the lock-in amplitude and the deviation of the forcing frequency from the natural oscillation frequency |ff - fn| is observed. Closed-loop control is then applied with the aim to suppress the PVC. The actuator lance is positioned in the wavemaker region, where the flow is most receptive. Magnitude and phase of the natural flow oscillation associated with the PVC are estimated from four hot-wire signals using an extended Kalman filter. The estimated PVC signal is phase-shifted and fed back to the actuator. PIV measurements reveal that feedback control achieves a reduction of the PVC oscillation energy of about 40 \%.}, note = {Paper No. GT2016-57686, pp. V04BT04A036}, url = {http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2555103}, publisher = {ASME}, booktitle = {Proceedings of ASME Turbo Expo 2016, June 13 - 17, 2016, Seoul, South Korea}, DOI = {10.1115/GT2016-57686}, author = {Kuhn, P. and Moeck, J. P. and Paschereit, C. O. and Oberleithner, K.} } @Inproceedings { rw2016:tschepe, title = {Cross-Flow Induced Pressure on Air Outlets}, year = {2016}, abstract = {This paper shows that the interaction of an air stream (jet) coming from the outlet of a vehicle with the surrounding flow has an important impact on the pressure distribution in the outlet duct. Based on experimental investigations carried out in a wind tunnel it is shown that this interaction in most cases causes an additional counter pressure that has to be overcome by the acting fan. Depending on the parameter setting pressure differences in the order of several hundred Pascal can appear. Here, the most important parameter for this interaction turned out to be the momentum flux ratio of exhaust jet and cross-flow. This ratio is a result of the streams' fluid densities and velocities and is strongly affected by the near wall flow profile of the cross-flow upstream the outlet. Furthermore, the impact of geometry parameters such as the jet's exit shape is demonstrated.}, note = {paper 44}, url = {http://dx.doi.org/10.4203/ccp.110.44}, editor = {Pombo, J.}, publisher = {Civil-Comp Press}, address = {Stirlingshire, United Kingdom}, booktitle = {The Third International Conference on Railway Technology: Research, Development and Maintenance}, ISSN = {1759-3433}, DOI = {10.4203/ccp.110.44}, reviewed = {1}, author = {Tschepe, J. and Weise, M. and Tietze, A. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Marten2016b, title = {Effects of Airfoil's Polar Data in the Stall Region on the Estimation of Darrieus Wind Turbine Performance}, year = {2016}, volume = {9}, pages = {11}, abstract = {Interest in vertical-axis wind turbines (VAWTs) is experiencing a renaissance after most major research projects came to a standstill in the mid 90's, in favour of conventional horizontal-axis turbines (HAWTs). Nowadays, the inherent advantages of the VAWT concept, especially in the Darrieus configuration, may outweigh their disadvantages in specific applications, like the urban context or floating platforms. To enable these concepts further, efficient, accurate, and robust aerodynamic prediction tools and design guidelines are needed for VAWTs, for which low-order simulation methods have not reached yet a maturity comparable to that of the Blade Element Momentum Theory for HAWTs' applications. The two computationally efficient methods that are presently capable of capturing the unsteady aerodynamics of Darrieus turbines are the Double Multiple Streamtubes (DMS) Theory, based on momentum balances, and the Lifting Line Theory (LLT) coupled to a free vortex wake model. Both methods make use of tabulated lift and drag coefficients to compute the blade forces. Since the incidence angles range experienced by a VAWT blade is much wider than that of a HAWT blade, the accuracy of polars in describing the stall region and the transition towards the ''thin plate like'' behaviour has a large effect on simulation results. This paper will demonstrate the importance of stall and post-stall data handling in the performance estimation of Darrieus VAWTs. Using validated CFD simulations as a baseline, comparisons are provided for a blade in VAWT-like motion based on a DMS and a LLT code employing three sets of post-stall data obtained from a wind tunnel campaign, XFoil predictions extrapolated with the Viterna-Corrigan model and a combination of them. The polar extrapolation influence on quasi-steady operating conditions is shown and azimuthal variations of thrust and torque are compared for exemplary tip-speed ratios (TSRs). In addition, the major relevance of a proper dynamic stall model into both simulation methods is highlighted and discussed.}, note = {Paper No. GT2016-56685, pp. V009T46A007}, url = {http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2555663}, publisher = {Seoul, South Korea, June 13-17, 2016}, series = {Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy}, booktitle = {ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition}, organization = {ASMe}, DOI = {10.1115/GT2016-56685}, author = {Marten, D. and Bianchini, A. and Pechlivanoglou, G. and Balduzzi, F. and Nayeri, C. N. and Ferrara, G. and Paschereit, C. O. and Ferrari, L.} } @Inproceedings { Stathopoulos2016a, title = {Emissions of a wet premixed flame of natural gas and a mixture with hydrogen at high pressure}, year = {2016}, volume = {Volume 4B: Combustion, Fuels and Emissions}, pages = {11}, abstract = {It is generally accepted that combustion of hydrogen and natural gas mixtures will become more prevalent in the near future, to allow for a further penetration of renewables in the European power generation system. The current work aims at the demonstration of the advantages of steam dilution, when highly reactive combustible mixtures are used in a swirl-stabilized combustor. To this end, high-pressure experiments have been conducted with a generic swirl-stabilized combustor featuring axial air injection to increase flashback safety. The experiments have been conducted with two fuel mixtures, at various pressure levels up to 9 bar and at four levels of steam dilution up to 25 \% steam-to-air mass flow ratio. Natural gas has been used as a reference fuel, whereas a mixture of natural gas and hydrogen (10 \% hydrogen by mass) represented an upper limit of hydrogen concentration in a natural gas network with hydrogen enrichment. The results of the emissions measurements are presented along with a reactor network model. The latter is applied as a means to qualitatively understand the chemical processes responsible for the observed emissions and their trends with increasing pressure and steam injection.}, note = {Paper No. GT2016-57745, pp. V04BT04A040}, url = {http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2555107\&resultClick=3}, publisher = {ASME}, booktitle = {Proceedings of ASME Turbo Expo 2016, June 13-17, 2016, Seoul, South Korea}, DOI = {10.1115/GT2016-57745}, author = {Stathopoulos, P. and Kuhn, P. and Wendler, J. and Tanneberger, T. and Terhaar, S. and Paschereit, C. O. and Schmalhofer, C. and Griebel, P. and Aigner, M.} } @Inproceedings { Holst2016a, title = {Potential of Retrofit Passive Flow Control for Small Horizontal Axis Wind Turbines}, year = {2016}, volume = {9}, pages = {11}, abstract = {The present paper analyzes the effect of passive flow control (PFC) with respect to the retrofitting on small horizontal axis wind turbines (sHAWT). We conducted extensive wind tunnel studies on an high performance low Reynolds airfoil using different PFC elements, i.e. vortex generators (VGs) and Gurney flaps. QBlade, an open source Blade Element Momentum (BEM) code, is used to study the retrofitting potential of a simulated small wind turbine. The turbine design is presented and discussed. The simulations include the data and polars gained from the experiments and give further insight into the effects of PFC on sHAWT. Therefore several different blades were simulated using several variations of VG positions. This paper discusses their influence on the turbine performance. The authors focus especially on the start-up performance as well as achieving increased power output at lower wind speeds. The vortex generators reduce the risk of laminar separation and enhance the lift in some configurations by more than 40\% at low Reynolds numbers.}, note = {Paper No. GT2016-56679}, publisher = {ASME}, series = {Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy}, booktitle = {ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy}, DOI = {10.1115/GT2016-56679}, author = {Holst, D. and Pechlivanoglou, G. and Wegner, F. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Wieser2016, title = {Quantitative Tuft Flow Visualization on the Volvo S60 under realistic driving Conditions}, year = {2016}, pages = {12}, url = {http://arc.aiaa.org/doi/10.2514/6.2016-1778}, publisher = {ARC AIAA}, booktitle = {54th AIAA Aerospace Sciences Meeting}, DOI = {10.2514/6.2016-1778}, author = {Wieser, D. and Bonitz, S. and Nayeri, C. N. and Paschereit, C. O. and Broniewicz, A. and Larsson, L. and L{\"o}fdahl, L.} } @Inproceedings { Host2016b, title = {sHAWT Design: Airfoil Aerodynamics Under the Influence of Roughness}, year = {2016}, volume = {9}, pages = {10}, abstract = {Small horizontal axis wind turbines (sHAWTs) are mostly designed by smaller companies with no or just small possibilities of aerodynamic testing and hence, airfoil selection is often based on published performance data and minimal or no experimental testing from the blade designer's side. This paper focuses on the aerodynamic consequences resulting from an unqualified airfoil selection and accumulating surface soiling. The high performance low Reynolds profile FX 63-137 is compared to an Eppler-338 wing section as well as to a high performance utility scale wind turbine airfoil, AH 93-W-174 -1ex. We extensively investigated these three different airfoils within the low Reynolds regime between 50,000 and 200,000. This regime is especially important for the starting behavior of a wind turbine, i.e. a quick speed up, and is crucial for small wind turbines because they have more frequent start/stop events. A Reynolds number of 200 k is additionally the operational regime of some sHAWT under the 5-10 kW level. The present study discusses not only the low Reynolds performance of the smooth profiles but investigates the influence of surface soiling. This ranges from 2D disturbances, such as a 0.2mm thin tripwire or several zigzag tapes, up to the simulation of massive sand build up by covering the entire leading edge region with a 40 grit sand paper. The experiments reveal that even small surface soiling has an impact and massive roughness leads in some cases to the loss of 50\% in lift coefficient. The experimental data is used to simulate a sHAWT in different stages of debris. While the peak power was reduced by two thirds compared to the clean configuration the annual energy production has halved under certain conditions.}, url = {http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2555661}, publisher = {ASME}, series = {Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy}, booktitle = {ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition}, event_name = {ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition}, DOI = {10.1115/GT2016-56377}, author = {Holst, D. and Pechlivanoglou, G. and Kohlrausch, C. T. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Reichel2016, title = {Shockless Explosion Combustion: Experimental Investigation of a new Approximate Constant Volume Combustion Process}, year = {2016}, volume = {4B}, abstract = {Approximate constant volume combustion (aCVC) is a promising way to achieve a step change in the efficiency of gas turbines. This work investigates a recently proposed approach to implement aCVC in a gas turbine combustion system: shockless explosion combustion (SEC). The new concept overcomes several disadvantages such as sharp pressure transitions, entropy generation due to shock waves, and exergy losses due to kinetic energy which are associated with other aCVC approaches like, e.g., pulsed detonation combustion. The combustion is controlled via the the fuel/air mixture distribution which is adjusted such that the entire fuel/air volume undergoes a spatially quasi-homogeneous autoignition. Accordingly, no shock waves occur and the losses associated with a detonation wave are not present in the proposed system. Instead, a smooth pressure rise is created due to the heat release of the homogeneous combustion. An atmospheric combustion test rig is designed to investigate the autoignition behavior of relevant fuels under intermittent operation, currently up to a frequency of 2Hz. Application of OH*- and dynamic pressure sensors allows for a spatially- and time-resolved detection of ignition delay times and locations. Dimethyl ether (DME) is used as fuel since it exhibits reliable autoignition already at 920K mixture temperature and ambient pressure. First, a model-based control algorithm is used to demonstrate that the fuel valve can produce arbitrary fuel profiles in the combustion tube. Next, the control algorithm is used to achieve the desired fuel stratification, resulting in a significant reduction in spatial variance of the auto-ignition delay times. This proves that the control approach is a useful tool for increasing the homogeneity of the autoignition.}, url = {http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2555102}, booktitle = {ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition}, DOI = {10.1115/GT2016-57680}, author = {Reichel, T. G. and Sch{\"a}pel, J. S. and Berndt, P. and King, R. and Klein, R. and Paschereit, C. O. and Christian, O.} } @Inproceedings { rw2016:tschep2, title = {Towing Tank Experiments for Train Aerodynamics}, year = {2016}, abstract = {This paper gives an overview on different experimental methods for the measurement of the aerodynamic drag of railroad vehicles in general as well as on the measurement of drag of submerged bodies in water in particular. It is shown that water based drag measurements with moving railroad models are very promising in terms of overcoming disadvantages in wind tunnel testing with scaled models. For this reason, a test setup in the water towing tank of the Technical University of Berlin is being developed to adapt the physical boundary conditions including high Reynolds numbers for more accurate results and the possibility to investigate full length model train compositions. Advantages and limitations of these experiments in water are discussed and preliminary results are presented.}, note = {paper 49}, url = {http://dx.doi.org/10.4203/ccp.110.49}, editor = {Pombo, J.}, publisher = {Civil-Comp Press}, address = {Stirlingshire, United Kingdom}, booktitle = {The Third International Conference on Railway Technology: Research, Development and Maintenance}, ISSN = {1759-3433}, DOI = {10.4203/ccp.110.49}, reviewed = {1}, author = {Tschepe, J. and Nayeri, C. N. and Schmidt, H.-J. and Paschereit, C. O.} } @Techreport { Wieser2016, title = {Surface Flow Visualization on a Full-Scale Passenger Car with Quantitative Tuft Image Processing}, year = {2016}, number = {2016-01-1582}, abstract = {Flow visualization techniques are widely used in aerodynamics to investigate the surface trace pattern. In this experimental investigation, the surface flow pattern over the rear end of a full-scale passenger car is studied using tufts. The movement of the tufts is recorded with a DSLR still camera, which continuously takes pictures. A novel and efficient tuft image processing algorithm has been developed to extract the tuft orientations in each image. This allows the extraction of the mean tuft angle and other such statistics. From the extracted tuft angles, streamline plots are created to identify points of interest, such as saddle points as well as separation and reattachment lines. Furthermore, the information about the tuft orientation in each time step allows studying steady and unsteady flow phenomena. Hence, the tuft image processing algorithm provides more detailed information about the surface flow than the traditional tuft method. The main advantages over other flow visualization methods, such as oil paint, is that experimental facilities are not contaminated and statistical data can be extracted.The investigated surface pattern shows a symmetric flow on the entire rear end section of the passenger car. The flow field on the roof, backlight, and upper trunk deck is attached almost everywhere. However, two small regions indicate the presence of two counter-rotating vortices at the lower edge of the backlight (rear window). Those vortices are also detectable in the distribution of the tuft angle standard deviation. A bifurcation line is present at each side of the trunk due to the streamwise vortices originating at the C-pillars. The tuft streamlines created with this novel tuft method are compared to a standard oil paint flow visualization to validate the calculated tuft flow pattern. A critical comparison between the methods confirms that the flow tuft analysis algorithm functions flawlessly as a highly detailed flow analysis tool without the mess of oil paint.}, url = {http://papers.sae.org/2016-01-1582/}, institution = {SAE Technical Paper, SAE 2016 World Congress and Exhibition}, type = {Technical Paper}, DOI = {10.4271/2016-01-1582}, author = {Wieser, D. and Bonitz, S. and L{\"o}fdahl, L. and Broniewicz, A. and Nayeri, C. N. and Paschereit, C. O. and Larsson, L.} } @Article { Vahl2015c, title = {Mixing enhancement of an axisymmetric jet using flaplets with zero mass-flux excitation}, journal = {Experiments in Fluids}, year = {2015}, month = {2}, volume = {56}, number = {38}, publisher = {Springer Berlin Heidelberg}, ISSN = {0723-4864 (print), 1432-1114 (online)}, DOI = {10.1007/s00348-014-1889-z}, author = {M{\"u}ller-Vahl, H. and Nayeri, C. N. and Paschereit, C. O. and Greenblatt, D.} } @Article { Cosic2014bb, title = {Acoustic response of Helmholtz dampers in the presence of hot grazing flow}, journal = {Journal of Sound and Vibration}, year = {2015}, volume = {335}, pages = {1-18}, ISSN = {0022-460X}, DOI = {/10.1016/j.jsv.2014.08.025}, author = {\'{C}osi\'{c}, B. and Wassmer, D. and Terhaar, S. and Paschereit, C. O.} } @Article { Schimek2015, title = {Amplitude-Dependent Flow Field and Flame Response to Axial and Tangential Velocity Fluctuations}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2015}, volume = {137}, number = {8}, number2 = {GTP-14-1525}, pages = {081501-1/10}, abstract = {The current paper investigates the nonlinear interaction of the flow field and the unsteady heat release rate and the role of swirl fluctuations. The test rig consists of a generic swirl-stabilized combustor fed with natural gas and equipped with a high-amplitude forcing device. The influence of the phase between axial and azimuthal velocity oscillations is assessed on the basis of the amplitude and phase relations between the velocity fluctuations at the inlet and the outlet of the burner. These relations are determined in the experiment with the Multi-Microphone-Method and a two component Laser-Doppler velocimeter. Particle image velocimetry and OH*-chemiluminescence measurements are conducted to study the interaction between the flow field and the flame. For several frequency regimes, characteristic properties of the forced flow field and flame are identified, and a strong amplitude dependence is observed. It is found that the convective time delay between the swirl generator and the flame has an important influence on swirl-number oscillations and the flame dynamics in the low-frequency regime. For mid and high frequencies, significant changes in the mean flow field and the mean flame position are identified for high forcing amplitudes. These affect the interaction between coherent structures and the flame and are suggested to be responsible for the saturation in the flame response at high forcing amplitudes.}, url = {http://gasturbinespower.asmedigitalcollection.asme.org/data/Journals/JETPEZ/0/GTP-14-1525.pdf}, DOI = {10.1115/1.4029368}, author = {Schimek, S. and \'{C}osi\'{c}, B. and Moeck, J. P. and Terhaar, S. and Paschereit, C. O.} } @Article { Kabiraj2015, title = {Chaos in an imperfectly premixed model combustor}, journal = {Chaos: An Interdisciplinary Journal of Nonlinear Science}, year = {2015}, volume = {25}, number = {2}, pages = {-}, url = {http://scitation.aip.org/content/aip/journal/chaos/25/2/10.1063/1.4906943}, DOI = {10.1063/1.4906943}, author = {Kabiraj, L. and Saurabh, A. and Karimi, N. and Sailor, A. and Mastorakos, E. and Dowling, A. P. and Paschereit, C. O.} } @Article { Kabiraj2015, title = {Coherence resonance in a thermoacoustic system}, journal = {Physical Review E}, year = {2015}, volume = {92}, number = {4}, abstract = {We experimentally investigated the noise-induced dynamics of a prototypical thermoacoustic system undergoing a subcritical Hopf bifurcation to limit cycle oscillations. The study was performed prior to the bistable regime. Analysis of the characteristics of pressure oscillations in the combustor and fluctuations in the heat release rate from the flame--the two physical entities involved in thermoacoustic coupling--at increasing levels of noise indicated precursors to the Hopf bifurcation. These precursors were further identified to be a result of coherence resonance.}, url = {http://dx.doi.org/10.1103/PhysRevE.92.042909}, publisher = {American Physical Society (\{APS\})}, DOI = {10.1103/physreve.92.042909}, author = {Kabiraj, L. and Steinert, R. and Saurabh, A. and Paschereit, C. O.} } @Article { Nayeri2015, title = {Collaborative research on wind turbine load control under realistic turbulent inflow conditions}, journal = {DEWEK 2015}, year = {2015}, abstract = {Modern turbines control load and power by actively adjusting the angle of attack via pitch variation. However, this technology is not suited for compensating the inflow variations generated by the atmospheric boundary layer or from upstream wind turbines (wind farms) or yaw errors, sudden gusts or turbulence which can occur within seconds or less and can have local impact on a rotor blade. In a collaborative research effort of five German universities, passive and active flow control methods for the alleviation of dynamic loads, load fluctuations and for reduction of wake effects are investigated, both experimentally and numerically. Furthermore, numerical tools suitable for evaluating the overall cost reduction and benefit of flow control methods on wind turbines will be validated and extended such that the results can be transferred to fullscale wind turbines under realistic inflow conditions.}, url = {http://15.dewek.de/fileadmin/downloads/Book_of_Abstracts_2015.pdf}, publisher = {DEWI}, author = {Nayeri, C. N. and Vey, S. and Marten, D. and Pechlivanoglu, G. and Paschereit, C. O.} } @Article { Nayeri2015, title = {Control of Thick Airfoil, Deep Dynamic Stall Using Steady Blowing}, journal = {AIAA Journal}, year = {2015}, volume = {53}, number = {2}, pages = {277-295}, DOI = {10.2514/1.J053090}, author = {Mueller-Vahl, H. and Strangfeld, C. and Nayeri, C. N. and Paschereit, C. O. and Greenblatt, D.} } @Article { Niether2015a, title = {Development of a Fluidic Actuator for Adaptive Flow Control on a Thick Wind Turbine Airfoil}, journal = {Journal of Turbomachinery}, year = {2015}, volume = {137}, number = {6}, pages = {061003 (10 pages)}, url = {http://asmedigitalcollection.asme.org/data/Journals/JOTUEI/0/TURBO-14-1229.pdf}, ISSN = {0889-504X}, DOI = {10.1115/1.4028654}, author = {Niether, S. and Bobusch, B. and Marten, D. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.} } @Article { Fischer2015, title = {Development of a medium scale research hawt for inflow and aerodynamics research in the large wind tunnel of TU Berlin}, journal = {DEWEK 2015}, year = {2015}, abstract = {The development of a medium scale research wind turbine is a part of the research project PAK 780 funded by the German Science Foundation (DFG). In this project six universities from all over Germany join forces and pursue fundamental research in the field of wind turbine aerodynamics, inflow turbulence as well as wake and flow control. The Modular Research Wind Turbine (MoReWiT) design and development is an integral part of this research program designed to assist the research tasks of all project partners. The PAK 780 project consists of HFI TU Berlin, RWTH Aachen, Univ. of Oldenburg, Univ. of Stuttgart and TU Darmstadt and it is one of the major DFG funded projects in wind energy.}, note = {Book of abstracts 2015}, url = {http://15.dewek.de/fileadmin/downloads/Book_of_Abstracts_2015.pdf}, publisher = {DEWI}, author = {Fischer, J. and Eisele, O. and Pichlivanoglou, G. and Vey, S. and Nayeri, C. N. and Paschereit, C. O.} } @Article { Schmidt2015b, title = {Drag reduction on a rectangular bluff body with base flaps and fluidic oscillators}, journal = {Experiments in Fluids}, year = {2015}, volume = {56}, number = {7}, publisher = {Springer Berlin Heidelberg}, ISSN = {0723-4864 (print), 1432-1114 (online)}, DOI = {10.1007/s00348-015-2018-3}, author = {Schmidt, H.-J. and Woszidlo, R. and Nayeri, C. N. and Paschereit, C. O.} } @Article { Hoffmann2015, title = {Drag Reduction using Base Flaps Combined with Vortex Generators and Fluidic Oscillators on a Bluff Body}, journal = {SAE Int. J. Passeng. Cars - Mech. Syst.}, year = {2015}, volume = {8}, number = {2}, number2 = {2015-01-2890}, pages = {705-712}, abstract = {The potential of drag reduction on a generic model of a heavy vehicle using base flaps operated in combination with flow control devices is investigated experimentally. Base flaps are well known as drag reduction devices for bluff bodies and heavy road vehicles. However, for optimal performance their deflection angle should typically not exceed 12\(^{\circ}\). In this paper the primary goal is to increase the usable range of the deflection angles by applying flow control. The secondary goal is to find the most suitable method for flow control. A comparison is made between triangular vortex generators and fluidic oscillators as passive and active flow control methods, respectively. Vortex generators have the advantage of being very simple devices but produce drag. Fluidic oscillators are also quite simple devices but require additional air supply. Their advantages are that they can be activated when needed and that they do not generate additional drag. The wind tunnel model used corresponds to the geometrical dimensions of a 10\% scaled model yielding a Reynolds number of 7·105. Various flap angles with a length of 100mm were attached to the base. Other geometrical parameters such as the height of the vortex generators were also varied as well as their axial position. The results show that base flaps deflected by 20\(^{\circ}\) combined with vortex generators reduce drag by 26\% compared to the baseline. At deflection angles of 22.5\(^{\circ}\) the passive and active concepts show similar drag reduction. Furthermore, possibilities for performance improvement of the active concept are identified.}, DOI = {10.4271/2015-01-2890}, author = {Hoffmann, F. and Schmidt, H. J. and Nayeri, C. N. and Paschereit, C. O.} } @Article { Rukes2015a, title = {Effect of initial vortex core size on the coherent structures in the swirling jet near field}, journal = {Exp. Fluids}, year = {2015}, volume = {56}, number = {10}, note = {accepted for publication}, DOI = {10.1007/s00348-015-2066-8}, author = {Rukes, L. and Sieber, M. and Paschereit, C. O. and Oberleithner, K.} } @Article { Paredes2015b, title = {Global and Local Hydrodynamic Stability Analysis as a Tool for Combustor Dynamics Modeling}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2015}, number2 = {GTP-15-1320}, publisher = {ASME}, ISSN = {0742-4795 (online), 1528-8919 (print)}, DOI = {10.1115/1.4031183}, author = {Paredes, P. and Theofilis, V. and Terhaar, S. and Oberleithner, K. and Paschereit, C. O.} } @Article { Marten2015, title = {Implementation, Optimization, and Validation of a Nonlinear Lifting Line-Free Vortex Wake Module Within the Wind Turbine Simulation Code QBLADE}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2015}, number = {137}, abstract = {The development of the next generation of large multi-megawatt wind turbines presents exceptional challenges to the applied aerodynamic design tools. Because their operation is often outside the validated range of current state of the art momentum balance models, there is a demand for more sophisticated, but still computationally efficient simulation methods. In contrast to the Blade Element Momentum Method (BEM) the Lifting Line Theory (LLT) models the wake explicitly by a shedding of vortex rings. The wake model of freely convecting vortex rings induces a time-accurate velocity field, as opposed to the annular averaged induction that is computed from the momentum balance, with computational costs being magnitudes smaller than those of a full CFD simulation. The open source code QBlade, developed at the Berlin Institute of Technology, was recently extended with a Lifting Line - Free Vortex Wake algorithm. The main motivation for the implementation of a LLT algorithm into QBlade is to replace the unsteady BEM code AeroDyn in the coupling to FAST to achieve a more accurate representation of the unsteady aerodynamics and to gain more information on the evolving rotor wake and flow-field structure. Therefore, optimization for computational efficiency was a priority during the integration and the provisions that were taken will be presented in short. The implemented LLT algorithm is thoroughly validated against other benchmark BEM, LLT and panel method codes and experimental data from the MEXICO and NREL Phase VI tests campaigns. By integration of a validated LLT code within QBlade and its database, the setup and simulation of LLT simulations is greatly facilitated. Simulations can be run from already existing rotor models without any additional input. Example use cases envisaged for the LLT code include; providing an estimate of the error margin of lower fidelity}, note = {GTP-15-1421}, url = {http://gasturbinespower.asmedigitalcollection.asme.org/article.aspx?articleid=2467296}, booktitle = {Journal of Engineering for Gas Turbines and Power}, DOI = {10.1115/1.4031872}, author = {Marten, D. and Lennie, M. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.} } @Article { Reichel2015c, title = {Increasing Flashback Resistance in Lean Premixed Swirl-Stabilized Hydrogen Combustion by Axial Air Injection}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2015}, volume = {137}, number = {7}, number2 = {GTP-14-1522}, pages = {071503 (9 pages)}, DOI = {10.1115/1.4029119}, author = {Reichel, T. G. and Terhaar, S. and Paschereit, C. O.} } @Article { Reichel2015b, title = {Investigation of Lean Premixed Swirl-Stabilized Hydrogen Burner with Axial Air Injection Using OH-PLIF Imaging}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2015}, volume = {137}, number = {11}, number2 = {GTP-15-1263}, pages = {111513 (10 pages)}, publisher = {ASME}, ISSN = {0742-4795 (online), 1528-8919 (print)}, DOI = {10.1115/1.4031181​}, author = {Reichel, T. G. and G{\"o}ckeler, K. and Paschereit, C. O.} } @Article { Terhaar2015b, title = {Investigation of the Global Mode in Swirling Combustor Flows: Experimental Observations and Local and Global Stability Analysis}, journal = {Procedia IUTAM}, year = {2015}, volume = {14}, pages = {553 - 562}, note = {IUTAM_ABCM Symposium on Laminar Turbulent Transition}, keywords = {Turbulent swirling flow}, url = {http://www.sciencedirect.com/science/article/pii/S2210983815001054}, ISSN = {2210-9838}, DOI = {10.1016/j.piutam.2015.03.079}, author = {Terhaar, S. and Paredes, P. and Oberleithner, K. and Theofilis, V. and Paschereit, C. O.} } @Article { TerhaarOP2014, title = {Key parameters governing the precessing vortex core in reacting flows: An experimental and analytical study}, journal = {Proceedings of the Combustion Institute}, year = {2015}, volume = {35}, number = {3}, pages = {3347-3354}, ISSN = {15407489}, DOI = {10.1016/j.proci.2014.07.035}, author = {Terhaar, S. and Oberleithner, K. and Paschereit, C. O.} } @Article { Goeckeler2015, title = {Laminar Burning Velocities and Emissions of Hydrogen-Methane-Air-Steam Mixtures}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2015}, volume = {137}, number = {3}, number2 = {GTP-14-1366}, pages = {031503 (8 pages)}, abstract = {Humidified gas turbines using steam generated from excess heat feature increased cycle efficiencies. Injecting the steam into the combustor reduces NOx emissions, flame temperatures, and burning velocities, promising a clean and stable combustion of highly reactive fuels such as hydrogen or hydrogen-methane blends. This study presents laminar burning velocities for methane and hydrogen-enriched methane (10 mol. \% and 50 mol. \%) at steam contents up to 30\% of the air mass flow. Experiments were conducted on prismatic Bunsen flames stabilized on a slot-burner, employing OH planar laser-induced fluorescence (OH-PLIF) as an indicator for flame front areas. The experimental burning velocities agree well with results from one-dimensional simulations using the GRI 3.0 mechanism. Burning velocities reduce nonlinearly with ascending steam mole fractions and more rapid compared to simulations using ''virtual H2O'' stemming from a chemical influence on reactions. Hydrogen enrichment increases burning velocities, extending the flammability range toward leaner and more humid mixtures. Additionally, measured NOx and CO emissions reveal a strong reduction in NOx emissions for increasing steam dilution rates, whereas CO curves are shifted toward higher equivalence ratios.}, url = {http://gasturbinespower.asmedigitalcollection.asme.org/data/Journals/JETPEZ/930944/gtp_137_03_031503.pdf}, ISSN = {0742-4795}, DOI = {10.1115/1.4028460}, author = {G{\"o}ckeler, K. and Kr{\"u}ger, O. and Paschereit, C. O.} } @Article { Wieser2015d, title = {Manipulation of the Aerodynamic Behavior of the DrivAer Model with Fluidic Oscillators}, journal = {SAE Int. J. Passeng. Cars - Mech. Syst.}, year = {2015}, volume = {8}, number = {2}, number2 = {2015-01-1540}, pages = {687-702}, abstract = {Abstract The effect of an active flow control method is investigated on a 1:4 scale realistic vehicle model called DrivAer with notchback geometry. The wind tunnel experiments are conducted at a Reynolds number of Re=3.0·106. Fluidic oscillators are applied at the c-pillars and at the upper rear edge of the window. The actuators are installed inside the hollow designed model emitting a high frequency sweeping jet. The spacing of the actuators, the mass flow rate, and the position of actuation are varied. The effect of the active flow control on the car is investigated with force and surface pressure measurements. The surface trace pattern is visualized with tufts for the active flow control cases and the baseline case. A tuft algorithm analyzes provides statistical data of the flow angles. Moreover, particle image velocimetry measurements are performed in the plane of symmetry for \(\beta\)=0\(^{\circ}\) to capture the flow field at the rear end and the wake.}, DOI = {10.4271/2015-01-1540}, author = {Wieser, D. and Lang, H. and Nayeri, C. N. and Paschereit, C. O.} } @Article { Thamsen2015, title = {Numerical analysis of blood damage potential of the Heartmate II and Heartware HVAD rotary blood pumps}, journal = {Artificial Organs (International Society for Artificial Organs, ISAO)}, year = {2015}, volume = {39}, number = {8}, pages = {651--659}, keywords = {Blood trauma, Left ventricular assist devices, Rotary blood pumps, Computational fluid dynamics, Blood damage}, ISSN = {1525-1594}, DOI = {10.1111/aor.12542}, author = {Thamsen, B. and Bl{\"u}mel, B. and Schaller, J. and Paschereit, C. O. and Affeld, K. and Goubergrits, L. and Kertzscher, U.} } @Article { Darvish2015a, title = {Numerical and Experimental Study on the Tonal Noise Generation of a Radial Fan}, journal = {Journal of Turbomachinery}, year = {2015}, volume = {137}, number = {10}, number2 = {TURBO-15-1063}, pages = {101500-1 (9 pages)}, publisher = {ASME}, ISSN = {0889-504X}, DOI = {10.1115/1.4030498}, author = {Darvish, M. and Frank, S. and Paschereit, C. O.} } @Article { Spiegelberg2015, title = {Passive load reduction in wind turbine blades with an adaptive camber airfoil}, journal = {DEWEK2015}, year = {2015}, abstract = {As wind turbines have developed in size, there is a growing need for an easy and safe transport of spare parts and materials inside the nacelle, due to longer transport ways. Besides reducing the production and installation costs, the third also very important factor for the industry is the cost of operation and maintenance. If time of maintenance could be reduced and made more efficient, with less risk of accidents, the industry would save cost. Terex has, with its brand Demag, in an innovative way developed a new solution for the wind industry, based on reliable technology. 1.2 Challenges How do you transport parts inside the large nacelles of today and tomorrow, when parts must be transported longer ways with the risk of accidents? Till now, a simple jib crane mounted in the back end of the nacelle was sufficient, but the reach of such a crane is limited in the new turbine sizes over 5 MW. Secondly when every minute is cost, also waiting time for lifting and lowering of parts with chain hoist, becomes crucial as towers now can be up to 180 meters high. Furthermore, as turbines are installed offshore, the need for a crane system with no hydraulics is important to keep maintenance cost as low as possible.}, url = {http://15.dewek.de/fileadmin/downloads/Book_of_Abstracts_2015.pdf}, author = {Spiegelberg, H. and Lennie, M. and Pechlivanoglou, G.} } @Article { Ostermann2015b, title = {Phase-Averaging Methods for the Natural Flowfield of a Fluidic Oscillator}, journal = {AIAA Journal}, year = {2015}, volume = {53}, number = {8}, pages = {2359--2368}, ISSN = {0001-1452}, DOI = {10.2514/1.J053717}, author = {Ostermann, F. and Woszidlo, R. and Nayeri, C. N. and Paschereit, C. O.} } @Article { Kabiraj2015b, title = {Recurrence Analysis of Combustion Noise}, journal = {AIAA Journal}, year = {2015}, volume = {53}, number = {5}, pages = {1199-1210}, ISSN = {0001-1452}, DOI = {10.2514/1.J053285}, author = {Kabiraj, L. and Saurabh, A. and Nawroth, H. and Paschereit, C. O.} } @Article { Stathopoulos2015b, title = {Retrofitting micro gas turbines for wet operation. A way to increase operational flexibility in distributed CHP plants}, journal = {Applied Energy}, year = {2015}, volume = {154}, pages = {438--446}, publisher = {Elsevier}, ISSN = {0306-2619}, DOI = {10.1016/j.apenergy.2015.05.034}, author = {Stathopoulos, P. and Paschereit, C. O.} } @Article { Oberleithner2013d, title = {Shear flow instabilities in swirl-stabilized combustors and their impact on the amplitude dependent flame response: A linear stability analysis}, journal = {Combustion and Flame}, year = {2015}, volume = {162}, number = {1}, pages = {86-99}, keywords = {Swirl flame}, url = {http://www.sciencedirect.com/science/article/pii/S0010218014002077}, ISSN = {0010-2180}, DOI = {10.1016/j.combustflame.2014.07.012}, author = {Oberleithner, K. and Schimek, S. and Paschereit, C. O.} } @Article { Sieber2015a, title = {Spectral proper orthogonal decomposition}, journal = {ArXiv e-prints}, year = {2015}, url = {http://arxiv.org/pdf/1508.04642}, author = {Sieber, M. and Oberleithner, K. and Paschereit, C. O.} } @Article { Oberleithner2015b, title = {Stability Analysis of Time-averaged Jet Flows: Fundamentals and Application}, journal = {Procedia IUTAM}, year = {2015}, volume = {14}, pages = {141 - 146}, note = {IUTAM_ABCM Symposium on Laminar Turbulent Transition}, keywords = {linear stability analysis}, url = {http://www.sciencedirect.com/science/article/pii/S2210983815000607}, ISSN = {2210-9838}, DOI = {10.1016/j.piutam.2015.03.034}, author = {Oberleithner, K. and Paschereit, C. O. and Soria, J.} } @Article { Woszidlo2015, title = {The time-resolved natural flow field of a fluidic oscillator}, journal = {Experiments in Fluids}, year = {2015}, volume = {56}, number = {6}, ISSN = {0723-4864 (print), 1432-1114 (online)}, DOI = {10.1007/s00348-015-1993-8}, author = {Woszidlo, R. and Ostermann, F. and Nayeri, C. N. and Paschereit, C. O.} } @Article { Terhaar2014c, title = {Vortex Breakdown Types and Global Modes in Swirling Combustor Flows with Axial Injection}, journal = {Journal of Propulsion and Power}, year = {2015}, volume = {31}, number = {1}, pages = {219-229}, DOI = {10.2514/1.B35217}, author = {Terhaar, S. and Reichel, T. G. and Schr{\"o}dinger, C. and Rukes, L. and Oberleithner, K. and Paschereit, C. O.} } @Article { Holst2015, title = {Wake Analysis of a Finite Width Gurney Flap}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2015}, volume = {138}, number = {6}, pages = {062602--062602}, url = {http://dx.doi.org/10.1115/1.4031709}, publisher = {ASME}, ISSN = {0742-4795}, DOI = {10.1115/1.4031709}, author = {Holst, D. and Bach, A. and Nayeri, C. N. and Paschereit, C. O. and Pechlivanoglou, G.} } @Article { Xydis2015, title = {Wind Turbine Waste Heat Recovery -- A Short-Term Heat Loss Forecasting Approach}, journal = {Challenges}, year = {2015}, number = {6}, pages = {188--201}, keywords = {wind; waste heat recovery; district heating}, url = {http://www.mdpi.com/2078-1547/6/2/188}, web_url = {challenges-nayeri-2015.pdf}, ISSN = {2078-1547}, DOI = {10.3390/challe6020188}, author = {Xydis, G. and Pechlivanoglou, G. and Nayeri, C. N.} } @Conference { Stathopoulos2015, title = {Thermodynamic evaluation of constant volume combustion for gas turbine power cycles}, year = {2015}, month = {11}, event_place = {Toranomon Hills, Tokyo, Japan}, event_name = {International Gas Turbine Congress IGTC}, event_date = {Nov 15-20, 2015}, author = {Stathopoulos, P. and Vinkeloe, J. and Paschereit, C. O.} } @Incollection { Gray2015, title = {An Experimental Study of Different Obstacle Types for Flame Acceleration and DDT}, year = {2015}, volume = {127}, pages = {265-279}, editor = {Rudibert King}, publisher = {Springer}, series = {Notes on Numerical Fluid Mechanics and Multidisciplinary Design}, booktitle = {Active Flow and Combustion Control 2014}, ISBN = {978-3-319-11966-3}, DOI = {10.1007/978-3-319-11967-0}, author = {Gray, J. and Paschereit, C. O. and Moeck, J. P.} } @Incollection { Oevermann2015, title = {Investigation of Equivalence Ratio Fluctuations on the Dynamics of Turbulent Lean Premixed Methane/Air Flames with a Linear-Eddy Model}, year = {2015}, volume = {127}, pages = {213-227}, editor = {Rudibert King}, publisher = {Springer}, series = {Notes on Numerical Fluid Mechanics and Multidisciplinary Design}, booktitle = {Active Flow and Combustion Control 2014}, ISBN = {978-3-319-11966-3}, DOI = {10.1007/978-3-319-11967-0}, author = {Oevermann, M. and Schr{\"o}dinger, C. and Paschereit, C. O.} } @Incollection { Bobusch2015a, title = {Investigation of Fluidic Devices for Mixing Enhancement for the Shockless Explosion Combustion Process}, year = {2015}, volume = {127}, pages = {281-297}, editor = {Rudibert King}, publisher = {Springer}, series = {Notes on Numerical Fluid Mechanics and Multidisciplinary Design}, booktitle = {Active Flow and Combustion Control 2014}, ISBN = {978-3-319-11966-3}, DOI = {10.1007/978-3-319-11967-0}, author = {Bobusch, B. and Berndt, P. and Paschereit, C. O. and Klein, R.} } @Inproceedings { Bluemel2015, title = {Modellierung der Blutsch{\"a}digung in Rotationsblutpumpen mit Eulerschem Ansatz in ANSYS CFX}, year = {2015}, month = {6}, day = {25}, booktitle = {Proceedings of 33th ANSYS Conference \& CADFEM Users Meeting, Jun 24-26, Bremen, Germany}, event_place = {Bremen, Germany}, event_name = {ANSYS Conference \& 33th CADFEM Users Meeting}, event_date = {June 24-26, 2015}, ISBN = {3-937523-12-X}, author = {Bl{\"u}mel, B. and Paschereit, C. O. and Thamsen, B. and Schaller, J.} } @Inproceedings { Lennie2015a, title = {A Review of Wind Turbine Polar Data and its Effect on Fatigue Loads Simulation Accuracy}, year = {2015}, number = {ASME Paper GT2015-43249}, pages = {V009T46A018 (13 pages)}, booktitle = {Proceedings of ASME Turbo Expo 2015, June 15-19, 2015, Montreal, Quebec, Canada}, ISBN = {978-0-7918-5680-2}, DOI = {10.1115/GT2015-43249}, author = {Lennie, M. and Pechlivanoglou, G. and Marten, D. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Schaepel2015a, title = {Adaptive Control of Mixture Profiles for a Combustion Tube}, year = {2015}, number = {ASME Paper GT2015-42027}, pages = {V04AT04A005 (12 pages)}, booktitle = {Proceedings of ASME Turbo Expo 2015, June 15-19, 2015, Montreal, Quebec, Canada}, ISBN = {978-0-7918-5668-0}, DOI = {10.1115/GT2015-42027}, author = {Sch{\"a}pel, J. S. and King, R. and Bobusch, B. and Moeck, J. P. and Paschereit, C. O.} } @Inproceedings { Schwadtke2015, title = {BeRT im gro{\ss}en Windkanal}, year = {2015}, pages = {218-221}, publisher = {VDE Verlag}, booktitle = {Virtuelle Instrumente in der Praxis 2015: Begleitband zum 20. VIP-Kongress}, ISBN = {978-3800736690}, author = {Schwadtke, U. and Holst, D. and Paschereit, C. O.} } @Inproceedings { Schimek2015c, title = {Blue Combustion: Stoichiometric Hydrogen-Oxygen Combustion Under Humidified Conditions}, year = {2015}, number = {ASME Paper GT2015-43149}, pages = {V04BT04A007 (7 pages)}, booktitle = {Proceedings of ASME Turbo Expo 2015, June 15-19, 2015, Montreal, Quebec, Canada}, ISBN = {978-0-7918-5669-7}, DOI = {10.1115/GT2015-43149}, author = {Schimek, S. and Stathopoulos, P. and Tanneberger, T. and Paschereit, C. O.} } @Inproceedings { Marten2015a, title = {Configuration and Numerical Investigation of the Adaptive Camber Airfoil as Passive Load Alleviation Mechanism for Wind Turbines}, year = {2015}, number = {AIAA paper no. 2015-3390}, booktitle = {AIAA Aviation, 33rd AIAA Applied Aerodynamics Conference, June 22-26, 2015, Dallas, Texas, USA}, ISBN = {978-1-62410-363-6}, DOI = {10.2514/6.2015-3390}, author = {Marten, D. and Spiegelberg, H. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O. and Cameron, T.} } @Inproceedings { Kuhn2015a, title = {Design and Assessment of a Fuel-Flexible Low Emission Combustor for Dry and Steam-Diluted Conditions}, year = {2015}, number = {ASME Paper GT2015-43375}, pages = {V04BT04A024 (11 pages)}, booktitle = {Proceedings of ASME Turbo Expo 2015, June 15-19, 2015, Montreal, Quebec, Canada}, ISBN = {978-0-7918-5669-7}, DOI = {10.1115/GT2015-43375}, author = {Kuhn, P. and Terhaar, S. and Reichel, T. G. and Paschereit, C. O.} } @Inproceedings { Gray2015a, title = {Effect of initial flow velocity on the flame propagation in obstructed channels}, year = {2015}, number = {AIAA paper no. 2015-1351}, booktitle = {AIAA SciTech, 53rd Aerospace Sciences Meeting, 5-9 January, Kissimmee, Florida, USA}, DOI = {10.2514/6.2015-1351}, author = {Gray, J. and Moeck, J. P. and Paschereit, C. O.} } @Inproceedings { Nawroth2015a, title = {Effects of Shear Layer Manipulation on Noise Emissions of a Turbulent Jet Flame}, year = {2015}, number = {AIAA paper no. 2015-0303}, booktitle = {AIAA SciTech, 53rd Aerospace Sciences Meeting, 5-9 January, Kissimmee, Florida, USA}, DOI = {10.2514/6.2015-0303}, author = {Nawroth, H. and Paschereit, C. O.} } @Inproceedings { Vey2015a, title = {Experimental and Numerical Investigations of a Small Research Wind Turbine}, year = {2015}, number = {AIAA paper no. 2015-3392}, booktitle = {AIAA Aviation, 33rd AIAA Applied Aerodynamics Conference, June 22-26, 2015, Dallas, Texas, USA}, ISBN = {978-1-62410-363-6}, DOI = {10.2514/6.2015-3392}, author = {Vey, S. and Marten, D. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Ostermann2015a, title = {Experimental Comparison between the Flow Field of Two Common Fluidic Oscillator Designs}, year = {2015}, number = {AIAA paper no. 2015-0781}, booktitle = {AIAA SciTech, 53rd Aerospace Sciences Meeting, 5-9 January, Kissimmee , Florida, USA}, DOI = {10.2514/6.2015-0781}, author = {Ostermann, F. and Woszidlo, R. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { VonGosen.2015, title = {Experimental Investigation of Compressibility Effects in a Fluidic Oscillator}, year = {2015}, number = {AIAA paper no. 2015-0782}, booktitle = {AIAA SciTech, 53rd Aerospace Sciences Meeting, 5-9 January, Kissimmee , Florida, USA}, DOI = {10.2514/6.2015-0782}, author = {Von Gosen, F. and Ostermann, F. and Woszidlo, R. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Bach2015a, title = {Experimental Investigation of the Aerodynamic Lift Response of an Active Finite Gurney Flap}, year = {2015}, author = {Bach, A. and Berg, R. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Bach2015b, title = {Experimental Investigation of the Aerodynamic Lift Response of an Active Finite Gurney Flap}, year = {2015}, number = {AIAA paper no. 2015-1270}, booktitle = {AIAA SciTech, 53rd Aerospace Sciences Meeting, 5-9 January, Kissimmee, Florida, USA}, DOI = {10.2514/6.2015-1270}, author = {Bach, A. and Berg, R. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Schmidt2015a, title = {Experimental Investigation of the Flow Field behind a Bluff Body Equipped with Fluidic Oscillators}, year = {2015}, number = {AIAA paper no. 2015-0786}, booktitle = {AIAA SciTech, 53rd Aerospace Sciences Meeting, 5-9 January, Kissimmee, Florida, USA}, DOI = {10.2514/6.2015-0786}, author = {Schmidt, H.-J. and Woszidlo, R. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Dolan2015a, title = {Experimental Study on the Interaction between Swirl-stabilized Nozzles for Isothermal Flowfields}, year = {2015}, number = {AIAA paper no. 2015-0929}, booktitle = {AIAA SciTech, 53rd Aerospace Sciences Meeting, 5-9 January, Kissimmee, Florida, USA}, DOI = {10.2514/6.2015-0929}, author = {Dolan, B. and Gomez, R. and Nawroth, H. and Pack, S. and Gutmark, E. J.} } @Inproceedings { Wieser2015a, title = {Experiments with Vortex Generators applied to a Notchback Car Model}, year = {2015}, number = {AIAA paper no. 2015-1236}, booktitle = {AIAA SciTech, 53rd Aerospace Sciences Meeting, 5-9 January, Kissimmee, Florida, USA}, DOI = {10.2514/6.2015-3392}, author = {Wieser, D. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Nawroth2015a, title = {Flow Fields of Manipulated Shear Layers of a Turbulent Jet Flame}, year = {2015}, number = {AIAA paper no. 2015-2316}, booktitle = {AIAA Aviation, 45th AIAA Fluid Dynamics Conference, June 22-25, 2015, Dallas, Texas, USA}, ISBN = {978-1-62410-362-9}, DOI = {10.2514/6.2015-2316}, author = {Nawroth, H. and Paschereit, C. O.} } @Inproceedings { Paredes2015a, title = {Global and Local Hydrodynamic Stability Analysis as a Tool for Combustor Dynamics Modeling}, year = {2015}, number = {ASME Paper GT2015-44173}, pages = {V04BT04A070 (10 pages)}, booktitle = {Proceedings of ASME Turbo Expo 2015, June 15-19, 2015, Montreal, Quebec, Canada}, ISBN = {978-0-7918-5669-7}, DOI = {10.1115/GT2015-44173}, author = {Paredes, P. and Theofilis, V. and Terhaar, S. and Oberleithner, K. and Paschereit, C. O.} } @Inproceedings { Marten2015a, title = {Implementation, Optimization and Validation of a Nonlinear Lifting Line Free Vortex Wake Module Within the Wind Turbine Simulation Code QBlade}, year = {2015}, number = {ASME Paper GT2015-43265}, pages = {V009T46A019 (11 pages)}, booktitle = {Proceedings of ASME Turbo Expo 2015, June 15-19, 2015, Montreal, Quebec, Canada}, ISBN = {978-0-7918-5680-2}, DOI = {10.1115/GT2015-43265}, author = {Marten, D. and Lennie, M. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Reichel2015d, title = {Investigation of Lean Premixed Swirl-Stabilized Hydrogen Burner With Axial Air Injection Using OH-PLIF Imaging}, year = {2015}, number = {ASME Paper GT2015-42491}, pages = {V04AT04A036 (13 pages)}, booktitle = {Proceedings of ASME Turbo Expo 2015, June 15-19, 2015, Montreal, Quebec, Canada}, ISBN = {978-0-7918-5668-0}, DOI = {10.1115/GT2015-42491}, author = {Reichel, T. G. and G{\"o}ckeler, K. and Paschereit, C. O.} } @Inproceedings { Huang2015a, title = {Numerical and Experimental Investigation of Wind Turbine Wakes}, year = {2015}, number = {AIAA paper no. 2015-2310}, booktitle = {AIAA Aviation, 45th AIAA Fluid Dynamics Conference, June 22-25, 2015, Dallas, Texas, USA}, ISBN = {978-1-62410-362-9}, DOI = {10.2514/6.2015-2310}, author = {Huang, X. and Vey, S. and Meinke, M. and Schroeder, W. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Tanneberger2015a, title = {Numerical Investigation of the Flow Field and Mixing in a Swirl-Stabilized Burner With a Non-Swirling Axial Jet}, year = {2015}, number = {ASME Paper GT2015-43382}, pages = {V04BT04A026 (12 pages)}, booktitle = {Proceedings of ASME Turbo Expo 2015, June 15-19, 2015, Montreal, Quebec, Canada}, ISBN = {978-0-7918-5669-7}, DOI = {10.1115/GT2015-43382}, author = {Tanneberger, T. and Reichel, T. G. and Kr{\"u}ger, O. and S., Terhaar and Paschereit, C. O.} } @Inproceedings { Stathopoulos2015a, title = {Operational Strategies of Wet Cycle Micro Gas Turbines and Their Economic Evaluation}, year = {2015}, number = {ASME Paper GT2015-42274}, pages = {V003T20A003 (13 pages)}, booktitle = {Proceedings of ASME Turbo Expo 2015, June 15-19, 2015, Montreal, Quebec, Canada}, ISBN = {978-0-7918-5667-3}, DOI = {10.1115/GT2015-42274}, author = {Stathopoulos, P. and Paschereit, C. O.} } @Inproceedings { Rukes2015a, title = {The influence of the inner shear layer on the suppression of the global mode in heated swirling jets}, year = {2015}, number = {AIAA paper no. 2015-0302}, booktitle = {AIAA SciTech, 53rd Aerospace Sciences Meeting, 5-9 January, Kissimmee, Florida, USA}, DOI = {10.2514/6.2015-0302}, author = {Rukes, L. and Sieber, M. and Oberleithner, K. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Castro2015a, title = {The Use of a New Fatigue Tool (ALBdeS) to Analyse the Effects of Vortex Generators on Wind Turbines}, year = {2015}, number = {ASME Paper GT2015-43198}, pages = {V009T46A016 (12 pages)}, booktitle = {Proceedings of ASME Turbo Expo 2015, June 15-19, 2015, Montreal, Quebec, Canada}, ISBN = {978-0-7918-5680-2}, DOI = {10.1115/GT2015-43198}, author = {Castro, O. and Lennie, M. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Strangfeld2015b, title = {Unsteady Thick Airfoil Aerodynamics: Experiments, Computation, and Theory}, year = {2015}, number = {AIAA paper no. 2015-3071}, booktitle = {AIAA Aviation, 45th AIAA Fluid Dynamics Conference, June 22-25, 2015, Dallas, Texas, USA}, ISBN = {978-1-62410-362-9}, DOI = {10.2514/6.2015-3071}, author = {Strangfeld, C. and Rumsey, C. L. and M{\"u}ller-Vahl, H. and Greenblatt, D. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Vey2015a, title = {Utility Scale Wind Turbine Yaw From a Flow Visualization View}, year = {2015}, number = {ASME Paper GT2015-43407}, pages = {V009T46A021 (6 pages)}, abstract = {Results from a quantitative tuft flow visualization of a utility scale wind turbine undergoing a yaw movement are presented. Based on the turbine's SCADA data suitable pre- and post-yaw timeframes were defined and the surface flowfields were analysed. A distinct asymmetry between the surface flow patterns of the 90\(^{\circ}\) and 270\(^{\circ}\) azimutal blade positions was observed in the pre-yaw timeframe. After the turbine yawed back into the wind the symmetry was restored. Yaw-misalignment is a source of dynamic loads which limit a turbine's life time. The characterization of the involved flow structures and their dynamics is an essential step towards possible future load alleviation techniques. The quantitative tuft flow visualization technique is a measurement tool that can be used to assess the surface flow field.}, booktitle = {Proceedings of ASME Turbo Expo 2015, June 15-19, 2015, Montreal, Quebec, Canada}, ISBN = {978-0-7918-5680-2}, DOI = {10.1115/GT2015-43407}, author = {Vey, S. and Lang, H. M. and Nayeri, C. N. and Paschereit, C. O. and Pechlivanoglou, G. and Weinzierl, G.} } @Inproceedings { Holst2015a, title = {Wake Analysis of a Finite Width Gurney Flap}, year = {2015}, number = {ASME Paper GT2015-43220}, pages = {V009T46A017 (13 pages)}, abstract = {The results of stereo Particle-Image-Velocimetry measurements are presented in this paper to gain further insight into the wake of a finite width Gurney flap. It is attached to an FX 63-137 airfoil which is known for a very good performance at low Reynolds numbers and is therefore used for small wind turbines and is most appropriate for tests in the low speed wind tunnel presented in this study. The Gurney flaps are a promising concept for load control on wind turbines but can have adverse side effects, e.g. shedding of additional vortices. The investigation focuses on frequencies and velocity distributions in the wake as well as on the structure of the induced tip vortices. Phase averaged velocity fields are derived of a Proper-Orthogonal-Decomposition based on the stereo PIV measurements. Additional hot-wire measurements were conducted to analyze the fluctuations downstream of the finite width Gurney flaps. Experiments indicate a general tip vortex structure that is independent from flap length but altered by the periodic shedding downstream of the flap. The influence of Gurney flaps on a small wind turbine is investigated by simulating a small 40 kW turbine in Q-Blade. They can serve as power control without the need of an active pitch system and the starting performance is additionally improved. The application of Gurney flaps imply tonal frequencies in the wake of the blade. Simulation results are used to estimate the resulting frequencies. However, the solution of Gurney flaps is a good candidate for large scale wind turbine implementation as well. A FAST simulation of the NREL 5MW turbine is used to generate realistic time series of the lift. The estimations of control capabilities predict a reduction in the standard deviation of the lift of up to 65\%. Therefore finite width Gurney flaps are promising to extend the lifetime of future wind turbines.}, booktitle = {Proceedings of ASME Turbo Expo 2015, June 15-19, 2015, Montreal, Quebec, Canada}, ISBN = {978-0-7918-5680-2}, DOI = {10.1115/GT2015-43220}, author = {Holst, D. and Bach, A. and Nayeri, C. N. and Paschereit, C. O. and Pechlivanoglou, G.} } @Inproceedings { Bach2015b, title = {Wake Vortex Field of an Airfoil Equipped with an Active Finite Gurney Flap}, year = {2015}, number = {AIAA paper no. 2015-1271}, booktitle = {AIAA SciTech, 53rd Aerospace Sciences Meeting, 5-9 January, Kissimmee , Florida, USA}, DOI = {10.2514/6.2015-1271}, author = {Bach, A. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.} } @Article { Oberleithner2013c, title = {On the impact of swirl on the growth of coherent structures}, journal = {Journal of Fluid Mechanics}, year = {2014}, month = {2}, volume = {741}, pages = {156--199}, url = {http://journals.cambridge.org/article_S0022112013006691}, ISSN = {1469-7645}, DOI = {10.1017/jfm.2013.669}, author = {Oberleithner, K. and Paschereit, C. O. and Wygnanski, I.} } @Article { PaschereitTCO2014, title = {Application of linear hydrodynamic stability analysis to reacting swirling combustor flows}, journal = {Journal of Fluid Science and Technology}, year = {2014}, volume = {9}, number = {3}, pages = {1-14}, url = {https://www.jstage.jst.go.jp/article/jfst/9/3/9_2014jfst0024/_pdf}, DOI = {10.1299/jfst.2014jfst0024}, author = {Paschereit, C. O. and Terhaar, S. and \'{C}osi\'{c}, B. and Oberleithner, K.} } @Article { Strangfeld2014b, title = {Experimental Comparison of the Aerodynamic Behavior of Fastback and Notchback DrivAer Models}, journal = {SAE Int. J. Passeng. Cars - Mech. Syst.}, year = {2014}, volume = {7}, number = {2}, number2 = {2014-01-0613}, pages = {682-691}, url = {http://papers.sae.org/2014-01-0613/}, publisher = {Society of Automobile Engineers}, event_name = {SAE 2014 World Congress \& Exhibition, October 21-22, Detroit, Michigan, USA}, DOI = {10.4271/2014-01-0613}, author = {Wieser, D. and Schmidt, H.-J. and M{\"u}ller, S. and Strangfeld, C. and Nayeri, C. N. and Paschereit, C. O.} } @Article { Vey2014a, title = {Extracting quantitative data from tuft flow visualizations on utility scale wind turbines}, journal = {Journal of Physics: Conference Series}, year = {2014}, volume = {524}, number = {1}, url = {http://iopscience.iop.org/1742-6596/524/1/012011/pdf/1742-6596_524_1_012011.pdf}, booktitle = {The Science of Making Torque from Wind 2014}, DOI = {10.1088/1742-6596/524/1/012011}, author = {Vey, S. and Lang, H. M. and Nayeri, C. N. and Paschereit, C. O. and Pechlivanoglou, G.} } @Article { Bach2014c, title = {Finite micro-tab system for load control on a wind turbine}, journal = {Journal of Physics: Conference Series}, year = {2014}, volume = {524}, number = {1}, url = {http://iopscience.iop.org/1742-6596/524/1/012082/pdf/1742-6596_524_1_012082.pdf}, booktitle = {The Science of Making Torque from Wind 2014}, DOI = {10.1088/1742-6596/524/1/012082}, author = {Bach, A. and Lennie, M. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.} } @Article { TerhaarKP2014, title = {Flow Field and Flame Dynamics of Swirling Methane and Hydrogen Flames at Dry and Steam-Diluted Conditions}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2014}, volume = {137}, number = {4}, pages = {041503 (10 pages)}, url = {http://gasturbinespower.asmedigitalcollection.asme.org/data/Journals/JETPEZ/931032/gtp_137_04_041503.pdf}, ISSN = {0742-4795}, DOI = {10.1115/1.4028392}, author = {Terhaar, S. and Kr{\"u}ger, O. and Paschereit, C. O.} } @Article { Terhaar2014, title = {Impact of shear flow instabilities on the magnitude and saturation of the flame response}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2014}, volume = {136}, number = {7}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-84894523472\&partnerID=40\&md5=e5e37c408d2911b049f5a071dbcfaed7}, publisher = {ASME}, ISSN = {0742-4795 (online), 1528-8919 (print)}, DOI = {10.1115/1.4026530}, author = {Terhaar, S. and \'{C}osi\'{c}, B. and Paschereit, C. O. and Oberleithner, K.} } @Article { Terhaar2014a, title = {Impact of Steam-Dilution on the Flame Shape and Coherent Structures in Swirl-Stabilized Combustors}, journal = {Combustion Science and Technology}, year = {2014}, volume = {186}, pages = {889-911}, abstract = {AbstractHumidified gas turbines and steam-injected gas turbines are promising technologies to lower the emissions and increase the efficiency and fuel flexibility of gas turbines. In the current study, the influence of steam-dilution on swirl-stabilized methane and hydrogen-fired flames is experimentally investigated at Reynolds numbers in the range of 22,000 to 32,000. Velocity fields and flame positions were measured using high-speed particle image velocimetry and OH* chemiluminescence. An extension of the quantitative light sheet technique was employed to estimate the temperature fields. The combined results reveal strong changes in the flame position, the velocity field, and the temperature field with increasing rates of steam dilution. In particular, three different flow and flame patterns are encountered: At dry conditions, a V-shaped flame stabilizes in a broad inner recirculation zone with low local turbulent kinetic energy; at moderate steam content, the flame changes into a trumpet-like shape; and at very high rates of steam-dilution, the flame detaches and shows an annular shape. The associated coherent flow structures are extracted from the PIV data employing proper orthogonal decomposition. The isothermal flow is dominated by a helical instability arising near the combustor inlet. This structure is completely suppressed for the dry flame and reappears for the heavily steam-diluted detached flame with similar shape and frequency as for the isothermal case. The flow field of the trumpet-like flame at intermediate to high steam dilution rates features a helical instability of lower frequency that is located further downstream than in the isothermal and very wet case. A conceptional explanation is presented that relates the suppression of the helical instability to the specific encountered temperature fields and flame shapes.}, url = {http://www.tandfonline.com/eprint/WaarDIijpj9TcDDGM7Xk/full}, DOI = {10.1080/00102202.2014.890597}, author = {Terhaar, S. and Oberleithner, K. and Paschereit, C. O.} } @Article { GokeSTRGKFGP2014, title = {Influence of Pressure and Steam Dilution on NOx and CO Emissions in a Premixed Natural Gas Flame}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2014}, volume = {139}, number = {091508}, pages = {1-8}, url = {http://gasturbinespower.asmedigitalcollection.asme.org/article.aspx?articleid=1838118\&resultClick=1}, ISSN = {0742-4795}, DOI = {10.1115/1.4026942}, author = {G{\"o}ke, S. and Schimek, S. and Terhaar, S. and Reichel, T. G. and G{\"o}ckeler, K. and Kr{\"u}ger, O. and Fleck, J. and Griebel, P. and Paschereit, C. O.} } @Article { Kruger2014, title = {Large eddy simulations of methane oxidation at ultra-wet conditions in a model gas turbine combustor applying detailed chemistry}, journal = {Journal of Fluid Science and Technology}, year = {2014}, volume = {9}, number = {3}, pages = {1--12}, DOI = {10.1299/jfst.2014jfst0040}, author = {Kr{\"u}ger, O. and Duwig, C. and Terhaar, S. and Paschereit, C. O.} } @Article { Cosic2014, title = {Nonlinear Instability Analysis for Partially Premixed Swirl Flames}, journal = {Combustion Science and Technology}, year = {2014}, volume = {186}, number = {6}, pages = {713--736}, url = {http://www.tandfonline.com/doi/pdf/10.1080/00102202.2013.876420}, ISSN = {0010-2202}, DOI = {10.1080/00102202.2013.876420}, author = {\'{C}osi\'{c}, B. and Moeck, J. P. and Paschereit, C. O.} } @Article { Goeckeler2013c, title = {Residence Time Distribution in a Swirling Flow at Nonreacting, Reacting, and Steam-Diluted Conditions}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2014}, volume = {136}, number = {4}, pages = {041505 (12 pages)}, ISSN = {0742-4795 (online), 1528-8919 (print)}, DOI = {10.1115/1.4026000}, author = {G{\"o}ckeler, K. and Terhaar, S. and Paschereit, C. O.} } @Article { Cosic2014aa, title = {Response of a swirl-stabilized flame to simultaneous perturbations in equivalence ratio and velocity at high oscillation amplitudes}, journal = {Combustion and Flame}, year = {2014}, volume = {162}, number = {4}, pages = {1046-1062}, note = {in press}, ISSN = {0010-2180}, DOI = {10.1016/j.combustflame.2014.09.025}, author = {\'{C}osi\'{c}, B. and Terhaar, S. and Moeck, J. P. and Paschereit, C. O.} } @Article { Bobusch2014c, title = {Shockless Explosion Combustion: An Innovative Way of Efficient Constant Volume Combustion in Gas Turbines}, journal = {Combustion Science and Technology}, year = {2014}, volume = {186}, number = {10-11}, pages = {1680-1689}, abstract = {Constant volume combustion (CVC) in gas turbines is a promising way to achieve a step change in the efficiency of such systems. The most widely investigated technique to implement CVC in gas turbine systems is pulsed detonation combustion (PDC). Unfortunately, the PDC is associated with several disadvantages, such as sharp pressure transitions, entropy generation due to shock waves, and exergy losses due to kinetic energy. This work proposes a new way to implement CVC in a gas turbine combustion system: shockless explosion combustion (SEC). This technique utilizes acoustic waves inside the combustor to fill and purge the combustion tube. The combustion itself is controlled via the ignition delay time of the fuel/air mixture. By adjusting the ignition delay in a way such that the entire fuel/air volume undergoes homogeneous auto-ignition, no shock waves occur. Accordingly, the losses associated with a detonation wave are not present in the proposed system. Instead, a smooth pressure rise is created due to the heat release of the homogeneous combustion. The current article explains the SEC process in detail, and presents the identified challenges. Solutions to these challenges and the numerical and experimental approach are presented subsequently alongside with first preliminary results of the numerical studies.}, DOI = {10.1080/00102202.2014.935624}, author = {Bobusch, B. and Berndt, P. and Paschereit, C. O. and Klein, R.} } @Conference { Wassmer2014, title = {Acoustic Response of Helmholtz Dampers in the Presence of Hot Grazing Flow}, year = {2014}, url = {http://www.efmc10.org/images/pdf/TIRSDAG_SAMLET_web.pdf}, booktitle = {10th European Fluid Mechanics Conference (EFMC10), Technical University of Denmark (DTU Lyngby), Copenhagen, 14-18 September}, author = {Wassmer, D. and \'{C}osi\'{c}, B. and Terhaar, S. and Paschereit, C. O.} } @Conference { Wieser2014c, title = {Aerodynamics of Ground Vehicles (Part I und II)}, year = {2014}, booktitle = {1. Aerodynamic Workshop at Chalmers University, G{\"o}teborg, Schweden}, author = {Wieser, D. and Schmidt, H.-J. and Nayeri, C. N. and Paschereit, C. O.} } @Conference { Nayeri2014g, title = {Drag Reduction on a Generic Tractor-Trailor Using Sweeping Jets in Combination with Flaps}, year = {2014}, url = {http://aerovehicles1.sciencesconf.org/conference/aerovehicles1/pages/2_Program_1.pdf}, booktitle = {First International Conference in Numerical and Experimental Aerodynamics of Road Vehicles and Trains (Aerovehicles 1), 23-25 June 2014, Bordeaux, France}, author = {Nayeri, C. N. and Woszidlo, R. and Stumper, T. and Schmidt, H.-J. and Paschereit, C. O.} } @Conference { Wieser2014b, title = {Experimente mit fluidischen Oszillatoren zur aktiven Str{\"o}mungskontrolle in der Fahrzeugaerodynamik}, year = {2014}, booktitle = {11. Tagung: Fahrzeug-Aerodynamik, Juli 2014, Haus der Technik, M{\"u}nchen}, author = {Wieser, D. and Schmidt, H.-J. and Nayeri, C. N. and Paschereit, C. O.} } @Conference { Paschereit2014f, title = {Taming turbulent flames}, year = {2014}, url = {http://www.igcs-chennai.org}, booktitle = {Invited Talk, IGCS Workshop on Improving Energy Sustainability - Conventional and Renewable, Dec. 4-5, Department of Civil Engineering, Indian Institute of Technology Madras, Chennai, India}, author = {Paschereit, C. O.} } @Conference { Stathopoulos2014, title = {The ultra-wet cycle for high efficiency, low emission gas turbines}, year = {2014}, booktitle = {European Turbine Network ETN: The Future of Gas Turbine Technology, 7th IGTC, Brussels, Belgium, Oct. 14-15}, author = {Stathopoulos, P. and Terhaar, S. and Schimek, S. and Paschereit, C. O.} } @Incollection { Gray2015b, title = {Non-reacting investigations of a pseudo-orifice for the purpose of enhanced deflagration to detonation transition}, year = {2014}, pages = {176-181}, note = {International Conference on Pulsating and Continuous Detonations}, editor = {Roy, G. D. and Frolov, S. M.}, publisher = {Torus Press}, series = {Combustion and Detonation Series}, booktitle = {Transient Combustion and Detonation Phenomena:Fundamentals and Applications}, author = {Gray, J. and Moeck, J. P. and Paschereit, C. O.} } @Inproceedings { Strangfeld2014a, title = {Airfoil subjected to high-amplitude free-stream oscillations: theory and experiments}, year = {2014}, publisher = {AIAA}, booktitle = {7th AIAA Theoretical Fluid Mechanics Conference, 16-20 June, Atlanta, GA, USA}, ISBN = {978-1-62410-293-6}, DOI = {0.2514/6.2014-2926}, author = {Strangfeld, C. and Mueller-Vahl, H. and Greenblatt, D. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Kirk2014a, title = {Comparative Study of CFD Solver Models for Modeling of Flow Over Wind Turbine Airfoils}, year = {2014}, number = {ASME Paper GT2014-25926}, pages = {V03BT46A019 (9 pages)}, url = {http://proceedings.asmedigitalcollection.asme.org/data/Conferences/ASMEP/80912/V03BT46A019-GT2014-25926.pdf}, booktitle = {Proceedings of ASME Turbo Expo 2014, June 16-20, 2014, D{\"u}sseldorf, Germany}, ISBN = {978-0-7918-4566-0}, DOI = {10.1115/GT2014-25926}, author = {Kirk, W. and Capece, V. R. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { MuellerVahl2014, title = {Control of Unsteady Aerodynamic Loads Using Adaptive Blowing}, year = {2014}, publisher = {AIAA}, booktitle = {32nd AIAA Applied Aerodynamics Conference, 16-20 June, Atlanta, GA, USA}, ISBN = {978-1-62410-288-2}, DOI = {10.2514/6.2014-2562}, author = {Mueller-Vahl, H. and Nayeri, C. N. and Paschereit, C. O. and Greenblatt, D.} } @Inproceedings { Matthew2014, title = {Development and Validation of a Modal Analysis Code for Wind Turbine Blades}, year = {2014}, number = {ASME Paper GT2014-27151}, pages = {V03BT46A031}, booktitle = {Proceedings of ASME Turbo Expo 2014, June 16-20, 2014, D{\"u}sseldorf, Germany}, ISBN = {978-0-7918-4566-0}, DOI = {10.1115/GT2014-27151}, author = {Matthew, L. and Marten, D. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Niether2014a, title = {Development of a Fluidic Actuator for Adaptive Flow Control on a Thick Wind Turbine Airfoil}, year = {2014}, number = {ASME Paper GT2014-25922}, pages = {V03BT46A018}, url = {http://asmedigitalcollection.asme.org/data/Conferences/ASMEP/80912/V03BT46A018-GT2014-25922.pdf}, booktitle = {Proceedings of ASME Turbo Expo 2014, June 16-20, 2014, D{\"u}sseldorf, Germany}, ISBN = {978-0-7918-4566-0}, DOI = {10.1115/GT2014-25922}, author = {Niether, S. and Bobusch, B. and Marten, D. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Reichel2014b, title = {Experimental Investigation of Flame Stability of Swirl-Stabilized, Lean Pre-mixed Hydrogen Flames}, year = {2014}, booktitle = {Proceedings of the 8th International Seminar on Flame Structures}, ISBN = {978-3-943685-96-1}, author = {Reichel, T. G. and Paschereit, C. O.} } @Inproceedings { Nayeri2014d, title = {Experiments on the influence of yaw on the aerodynamic behaviour of realistic car geometries}, year = {2014}, pages = {43-51}, publisher = {Woodhead Publishing}, booktitle = {International Vehicle Aerodynamics Conference, 14-15 October, Loughboriugh, UK}, ISBN = {978-0-08-100199-8 (print), 978-0-08-100245-2 (online)}, author = {Nayeri, C. N. and Wieser, D. and Schmidt, H.-J. and Strangfeld, C. and Paschereit, C. O.} } @Inproceedings { TerhaarKP2014_2, title = {Flow Field and Flame Dynamics of Swirling Methane and Hydrogen Flames at Dry and Steam-Diluted Conditions}, year = {2014}, number = {ASME Paper GT2014-27023}, booktitle = {Proceedings of ASME Turbo Expo 2014, June 16-20, 2014, D{\"u}sseldorf, Germany}, author = {Terhaar, S. and Kr{\"u}ger, O. and Paschereit, C. O.} } @Inproceedings { Nawroth2014, title = {Flow Investigation and Acoustic Measurements of a Turbulent Jet Flame}, year = {2014}, number = {AIAA paper no. 2014-2255}, url = {http://arc.aiaa.org/doi/abs/10.2514/6.2014-2255}, booktitle = {11th AIAA/ASME Joint Thermophysics and Heat Transfer Conference, June 16-20, 2014, Atlanta, GA, USA}, DOI = {10.2514/6.2014-2255}, author = {Nawroth, H. and Paschereit, C. O.} } @Inproceedings { ReichelTP2014, title = {Increasing Flashback Resistance in Lean Premixed Swirl-Stabilized Hydrogen Combustion by Axial Air Injection}, year = {2014}, number = {ASME Paper: GT2014-27002}, booktitle = {Proceedings of ASME Turbo Expo 2014, June 16-20, 2014, D{\"u}sseldorf, Germany}, author = {Reichel, T. G. and Terhaar, S. and Paschereit, C. O.} } @Inproceedings { Gockeler2014b, title = {Laminar Burning Velocities and Emissions of Hydrogen-Methane-Air-Steam Mixtures}, year = {2014}, number = {ASME Paper GT2014-26811}, pages = {V04BT04A042 (10 pages)}, booktitle = {Proceedings of ASME Turbo Expo 2014, June 16-20, 2014, D{\"u}sseldorf, Germany}, ISBN = {978-0-7918-4569-1}, DOI = {10.1115/GT2014-26811}, author = {Katharina, K. and Kr{\"u}ger, O. and Paschereit, C. O.} } @Inproceedings { Kruger2014a, title = {Numerical Modeling and Validation of the Wind Flow Over the Lake Wannsee}, year = {2014}, volume = {c}, number = {Wccm Xi}, pages = {5217--5228}, url = {http://www.wccm-eccm-ecfd2014.org/admin/files/filePaper/p3072.pdf}, editor = {Onate, E. and Oliver, J. and Huerta, A.}, booktitle = {Proceedings of the 6th European Conference on Computational Fluid Dynamics, 20-25 July, Barcelona, Spain}, author = {Kr{\"u}ger, O. and Schr{\"o}dinger, C. and Lengwinat, A. and Paschereit, C. O.} } @Inproceedings { Ostermann2014a, title = {Phase-Averaging Methods for a Naturally Oscillating Flow Field}, year = {2014}, number = {AIAA paper no. 2014-1142}, url = {http://arc.aiaa.org/doi/abs/10.2514/6.2014-1142}, booktitle = {AIAA SciTech, 52nd Aerospace Sciences Meeting, January 13- 17, 2014, National Harbor, MD, USA}, ISBN = {978-1-62410-256-1}, DOI = {10.2514/6.2014-1142}, author = {Ostermann, F. and Woszidlo, R. and G{\"a}rtlein, S. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Kabiraj2014, title = {Recurrence Analysis of Combustion Generated Noise}, year = {2014}, number = {AIAA paper no. 2014-0623}, url = {http://arc.aiaa.org/doi/abs/10.2514/6.2014-0623}, booktitle = {AIAA SciTech, 52nd Aerospace Sciences Meeting, January 13- 17, 2014, National Harbor, MD, USA}, ISBN = {978-1-62410-256-1}, DOI = {10.2514/6.2014-0623}, author = {Kabiraj, L. and Nawroth, H. and Saurabh, A. and Paschereit, C. O.} } @Inproceedings { Wassmer2014, title = {Resonance Frequency of Helmholtz Dampers in the Presence of High-Temperature Grazing Flows}, year = {2014}, publisher = {American Institute of Aeronautics and Astronautics}, booktitle = {AIAA Aviation}, ISSN = {0010-2202}, DOI = {10.2514/6.2014-3179}, author = {Wassmer, D. and \'{C}osi\'{c}, B. and Paschereit, C. O.} } @Inproceedings { Saurabh2014a, title = {Swirl Flame Response to Traveling Acoustic Waves}, year = {2014}, number = {ASME Paper GT2014-26829}, pages = {V04BT04A043 (9 pages)}, url = {http://proceedings.asmedigitalcollection.asme.org/data/Conferences/ASMEP/80916/V04BT04A043-GT2014-26829.pdf}, booktitle = {Proceedings of ASME Turbo Expo 2014, June 16-20, 2014, D{\"u}sseldorf, Germany}, ISBN = {978-0-7918-4569-1}, DOI = {10.1115/GT2014-26829}, author = {Saurabh, A. and Steinert, R. and Moeck, J. P. and Paschereit, C. O.} } @Inproceedings { Ostermann2014a, title = {The Time-Resolved Internal and External Flow Field Properties of a Fluidic Oscillator}, year = {2014}, number = {AIAA paper no. 2014-1143}, url = {http://arc.aiaa.org/doi/abs/10.2514/6.2014-1143}, booktitle = {AIAA SciTech, 52nd Aerospace Sciences Meeting, January 13- 17, 2014, National Harbor, MD, USA}, ISBN = {978-1-62410-256-1}, DOI = {10.2514/6.2014-1143}, author = {G{\"a}rtlein, S. and Woszidlo, R. and Ostermann, F. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Geiser2014a, title = {Thermoacoustics of a turbulent premixed flame}, year = {2014}, number = {AIAA paper no. 2015-2476}, booktitle = {AIAA Aviation, 13th AIAA/CEAS Aeroacoustics Conference, 16-20 June 2014, Atlanta, Georgia, USA}, ISBN = {978-1-62410-285-1}, DOI = {10.2514/6.2014-2476}, author = {Geiser, G. and Nawroth, H. and Hosseinzadeh, A. and Zhang, F. and Bockhorn, H. and Habisreuther, P. and Janicka, J. and Paschereit, C. O. and Schroeder, W.} } @Inproceedings { Vahl2014, title = {Thick Airfoil Deep Dynamic Stall}, year = {2014}, volume = {2}, pages = {35-40}, url = {http://dx.doi.org/10.1007/978-3-642-54696-9_6}, editor = {H{\"o}lling, Michael and Peinke, Joachim and Ivanell, Stefan}, publisher = {Springer Berlin Heidelberg}, series = {Research Topics in Wind Energy}, booktitle = {Wind Energy - Impact of Turbulence}, language = {English}, ISBN = {978-3-642-54695-2}, DOI = {10.1007/978-3-642-54696-9_6}, author = {Mueller-Vahl, H. and Strangfeld, C. and Nayeri, C. N. and Paschereit, C. O. and Greenblatt, D.} } @Inproceedings { Pechlivanoglou2014a, title = {Utilization of Modern Large Scale HAWT Blade Design Techniques for the Development of Small HAWT Blades}, year = {2014}, number = {ASME Paper GT2014-25309}, pages = {V03BT46A005 (9 pages)}, url = {http://proceedings.asmedigitalcollection.asme.org/data/Conferences/ASMEP/80912/V03BT46A005-GT2014-25309.pdf}, booktitle = {Proceedings of ASME Turbo Expo 2014, June 16-20, 2014, D{\"u}sseldorf, Germany}, ISBN = {978-0-7918-4566-0}, DOI = {10.1115/GT2014-25309}, author = {Pechlivanoglou, G. and Weinzierl, G. and Masmanidis, I. and Nayeri, C. N. and Philippidis, T. and Paschereit, C. O.} } @Article { Bobusch2013b, title = {Optical Measurement of Local and Global Transfer Functions for Equivalence Ratio Fluctuations in a Turbulent Swirl Flame}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2013}, month = {11}, day = {1}, volume = {136}, number = {2}, pages = {021506}, ISSN = {0742-4795 (online), 1528-8919 (print)}, DOI = {10.1115/1.4025375}, author = {Bobusch, B. and \'{C}osi\'{c}, B. and Moeck, J. P. and Paschereit, C. O.} } @Article { OberleithnerTRP2013, title = {Why Non-Uniform Density Suppress the Precessing Vortex Core}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2013}, month = {9}, day = {23}, volume = {135}, number = {12}, pages = {121506 (9 Pages)}, ISSN = {0742-4795 (online), 1528-8919 (print)}, DOI = {10.1115/1.4025130}, author = {Oberleithner, K. and Terhaar, S. and Rukes, L. and Paschereit, C. O.} } @Article { Krebs2013, title = {Comparison of Nonlinear to Linear Thermoacoustic Stability Analysis of a Gas Turbine Combustion System}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2013}, month = {6}, day = {24}, volume = {135}, number = {8}, pages = {081503 (8 Pages)}, ISSN = {0742-4795 (online), 1528-8919 (print)}, DOI = {10.1115/1.4023887}, author = {Krebs, W. and Krediet, H. and Hermeth, S. and Poinsot, T. E. P. and Schimek, S. and Paschereit, C. O.} } @Article { Marten2013c, title = {qblade: an open source tool for design and simulation ofhorizontal and vertical axis wind turbines}, journal = {International Journal of Emerging Technology and Advanced Engineering (IJETAE)}, year = {2013}, month = {2}, volume = {3}, number = {special issue 3}, pages = {264-269}, url = {http://www.ijetae.com/files/Conference\%20ICERTSD-2013/IJETAE_ICERTSD_0213_41.pdf}, ISSN = {2250-2459 (Online)}, author = {Marten, D. and Wendler, J. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.} } @Article { Krueger2013, title = {Large Eddy Simulations of Hydrogen Oxidation at Ultra-Wet Conditions in a Model Gas Turbine Combustor Applying Detailed Chemistry}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2013}, month = {1}, day = {3}, volume = {135}, number = {2}, pages = {021501 (10 pages)}, url = {http://link.aip.org/link/?GTP/135/021501/1}, publisher = {ASME}, ISSN = {0742-4795 (online), 1528-8919 (print)}, DOI = {10.1115/1.4007718}, author = {Kr{\"u}ger, O. and Terhaar, S. and Paschereit, C. O. and Duwig, C.} } @Article { LacosteMPL2013, title = {Effect of Plasma Discharges on Nitric Oxide Emissions in a Premixed Flame}, journal = {Journal of Propulsion and Power}, year = {2013}, volume = {29}, number = {3}, pages = {748-751}, publisher = {American Institute of Aeronautics and Astronautics}, ISSN = {0748-4658, EISSN: 1533-3876}, DOI = {10.2514/1.B34819}, author = {Lacoste, D. A. and Moeck, J. P. and Paschereit, C. O. and Laux, C. O.} } @Article { Albin2013b, title = {Experimental investigation of burning velocities of ultra-wet methane-air-steam mixtures}, journal = {Fuel Processing Technology}, year = {2013}, volume = {107}, pages = {27--35}, abstract = {Global burning velocities of methane-air-steam mixtures are measured on prismatic laminar Bunsen flames and lifted turbulent V-flames for various preheating temperatures, equivalence ratios and steam mixture fractions at atmospheric pressure. Experiments are conducted on a new rectangular slot-burner. Experimental burning velocities are compared to computed flame speeds of one dimensional adiabatic premixed flames using detailed mechanisms (Konnov 0.5 and GRI Mech 3.0). Mean profiles of radicals OH* are also extracted from these flames and compared to simulation results.}, url = {http://www.sciencedirect.com/science/article/pii/S0378382012002652}, ISSN = {0378-3820}, DOI = {10.1016/j.fuproc.2012.06.027}, author = {Albin, E. and Nawroth, H. and G{\"o}ke, S. and D'Angelo, Y. and Paschereit, C. O.} } @Article { Bobusch2013d, title = {Experimental study of the internal flow structures inside a fluidic oscillator}, journal = {Experiments in Fluids}, year = {2013}, volume = {54}, number = {6}, pages = {1-12}, abstract = {The internal flow characteristics of a fluidic oscillator were investigated experimentally. Particle image velocimetry and time-resolved pressure measurements were employed in water to visualize and quantify the internal flow patterns. The method of proper orthogonal decomposition was applied to random flow field snap shots for phase reconstruction of one oscillation cycle. The resulting phase-averaged information provides detailed insight into the oscillation mechanism as well as into the interaction between the main chamber of the oscillator and its feedback channels. A growing recirculation bubble between the main jet and the attachment wall is identified as an underlying mechanism that causes the main jet to oscillate. The flow field measurements are complemented by time-resolved pressure measurements at various internal locations which yield additional comprehension of the switching behavior and accompanying timescales. Geometrical features, in particular at the inlet and outlet of the mixing chamber, are found to have a crucial impact on important flow characteristics such as oscillation frequency and jet deflection.}, url = {http://link.springer.com/content/pdf/10.1007\%2Fs00348-013-1559-6.pdf}, publisher = {Springer-Verlag}, ISSN = {0723-4864 (print), 1432-1114 (online)}, DOI = {10.1007/s00348-013-1559-6}, author = {Bobusch, B. and Woszidlo, R. and Bergada, J. M. and Nayeri, C. N. and Paschereit, C. O.} } @Article { Goeke2012b, title = {Influence of steam dilution on the combustion of natural gas and hydrogen in premixed and rich-quench-lean combustors}, journal = {Fuel Processing Technology}, year = {2013}, number = {107}, pages = {14-22}, url = {http://www.sciencedirect.com/science/article/pii/S0378382012002408}, web_url = {Goeke_FuProc2012.pdf}, ISSN = {0378-3820}, DOI = {10.1016/j.fuproc.2012.06.019}, author = {G{\"o}ke, S. and F{\"u}ri, M. and Bourque, G. and Bobusch, B. and G{\"o}ckeler, K. and Kr{\"u}ger, O. and Schimek, S. and Terhaar, S. and Paschereit, C. O.} } @Article { zhang2013, title = {On prediction of combustion generated noise with the turbulent heat release rate}, journal = {Acta Acustica united with Acustica}, year = {2013}, volume = {99}, number = {6}, pages = {940-951}, DOI = {10.3813/AAA.918673}, author = {Zhang, F. and Habisreuther, P. and Bockhorn, H. and Nawroth, H. and Paschereit, C. O.} } @Conference { saurabh2013c, title = {Effects of Swirl Intensity on Flame-response to Transverse Acoustic Forcing}, year = {2013}, booktitle = {Euromech Colloquium 546: Combustion Dynamics and Combustion Noise, May 13-16, 2013, Menaggio, Italy}, author = {Saurabh, A. and Paschereit, C. O.} } @Conference { nawroth2013d, title = {Experimental Investigation of the Noise Emitted from an Unconfined Premixed Flame}, year = {2013}, booktitle = {Euromech Colloquium 546: Combustion Dynamics and Combustion Noise, May 13-16, 2013, Menaggio, Italy}, author = {Nawroth, H. and Moeck, J. P. and Paschereit, C. O.} } @Conference { Gray2013c, title = {Investigations of the Dynamics of a Propagating Flame using High-Speed Imaging and Laser Sheet Tomography}, year = {2013}, number = {\#193}, booktitle = {Proceedings of the 24th International Colloquium on the Dynamics of Explosions and Reactive Systems (ICDERS) 28 July - 2 August 2013, Taipei, Taiwan (Republic of China)}, author = {Gray, J. and Moeck, J. P. and Paschereit, C. O.} } @Conference { nawroth2013e, title = {Large Eddy Simulation of Premixed Flames Using F-Tacles and ATF Approaches}, year = {2013}, booktitle = {Euromech Colloquium 546: Combustion Dynamics and Combustion Noise, May 13-16, 2013, Menaggio, Italy}, author = {Hosseinzadeh, A. and Nawroth, H. and Janicka, J. and Paschereit, C. O.} } @Conference { nawroth2013f, title = {Numerical and Experimental Investigation of the Noise Emitted by a Premixed Flame at Various Operating Conditions}, year = {2013}, booktitle = {Euromech Colloquium 546: Combustion Dynamics and Combustion Noise, May 13-16, 2013, Menaggio, Italy}, author = {Geiser, G. and Hosseinzadeh, A. and Nawroth, H. and Zhang, F. and Schr{\"o}der, J. and Janicka, J. and Paschereit, C. O. and Habisreuther, P. and Bockhorn, H.} } @Conference { Bobusch2013e, title = {Shockless Explosion Combustion --- An Innovative Way of Efficient Constant Volume Combustion in Gas Turbines ---}, year = {2013}, number = {\#181}, booktitle = {Proceedings of the 24th International Colloquium on the Dynamics of Explosions and Reactive Systems (ICDERS) 28 July - 2 August 2013, Taipei, Taiwan (Republic of China)}, author = {Bobusch, B. and Berndt, P. and Paschereit, C. O. and Klein, R.} } @Conference { saurabh2013e, title = {Transverse Acoustic Forcing Effects on an Annular Swirling Jet}, year = {2013}, booktitle = {3rd International Symposium on Bifurcations and Instabilities in Fluid Dynamics (BIFD 2013), July 8-11, 2013, Technion, Haifa, Israel}, author = {Saurabh, A. and Paschereit, C. O.} } @Inproceedings { PaschereitTOo2013, title = {Application of Linear Hydrodynamic Stability Analysis to Reacting Swirling Combustor Flows}, year = {2013}, booktitle = {Proceedings of 4th International Conference on Jets, Wakes and Separated Flows (ICJWSF), Sep 17-21, 2013, Nagoya, Aichi, Japan}, ISBN = {978-4-88898-234-4 (CD)}, author = {Paschereit, C. O. and Terhaar, S. and Oberleithner, K. and \'{C}osi\'{c}, B.} } @Inproceedings { Gockeler2013, title = {Burning Velocities of Hydrogen-Methane-Air Mixtures at Highly Steam-Diluted Conditions}, year = {2013}, pages = {1--6}, publisher = {Japan Society of Mechanical Engineers}, address = {Nagoya}, booktitle = {Proceedings of 4th International Conference on Jets, Wakes and Separated Flows (ICJWSF), Sep 17-21, 2013, Nagoya, Aichi, Japan}, ISBN = {978-4-88898-234-4 (CD)}, author = {G{\"o}ckeler, K. and Albin, E. and Kr{\"u}ger, O. and Paschereit, C. O.} } @Inproceedings { kabiraj2013b, title = {Characteristics of Acoustic Fluctuations Associated with a Premixed Turbulent V-flame}, year = {2013}, number = {P4-60}, pages = {6 pages}, booktitle = {Proceedings of the 6th European Combustion Meeting (ECM), June 25-28, 2013, Lund, Sweden}, ISBN = {978-91-637-2151-9}, author = {Kabiraj, L. and Nawroth, H. and Saurabh, A. and Paschereit, C. O.} } @Inproceedings { saurabh2013a, title = {Combustion Instability in a swirl flow combustor with transverse extensions}, year = {2013}, volume = {Volume 1B: Combustion, Fuels and Emissions}, number = {ASME paper GT2013-95732}, pages = {V01BT04A057}, url = {http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=1775958}, booktitle = {Proc. ASME Turbo Expo 2013, June 3-7, San Antonio, Texas, USA}, ISBN = {978-0-7918-5511-9}, DOI = {10.1115/GT2013-95732}, author = {Saurabh, A. and Paschereit, C. O.} } @Inproceedings { MoeckLLP2013, title = {Control of combustion dynamics in a swirl-stabilized combustor with nanosecond repetitively pulsed discharges}, year = {2013}, number = {AIAA paper no. 2013-0565}, url = {http://arc.aiaa.org/doi/pdfplus/10.2514/6.2013-565}, booktitle = {51st AIAA Aerospace Science Meeting, Grapevine, Texas, USA, Jan. 07-10}, DOI = {10.2514/6.2013-565}, author = {Moeck, J. P. and Lacoste, D. A. and Laux, C. O. and Paschereit, C. O.} } @Inproceedings { Marten2013b, title = {Development and Application of a Simulation Tool for Vertical and Horizontal Axis Wind Turbines}, year = {2013}, number = {ASME paper GT2013-94979}, pages = {V008T44A017 (9 pages)}, booktitle = {Proc. ASME Turbo Expo 2013, June 3-7, San Antonio, Texas, USA}, ISBN = {978-0-7918-5529-4}, DOI = {10.1115/GT2013-94979}, author = {Marten, D. and Wendler, J. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { saurabh2013b, title = {Effects of Transverse Acoustic Forcing on the Vortex Breakdown Zone: Investigation on an Annular Swirling Jet}, year = {2013}, number = {P1-24}, booktitle = {Proceedings of the 6th European Combustion Meeting (ECM), June 25-28, 2013, Lund, Sweden}, ISBN = {978-91-637-2151-9}, author = {Saurabh, A. and Paschereit, C. O.} } @Inproceedings { Schimek2013, title = {Emission formation of liquid fuel combustion under humidified conditions}, year = {2013}, number = {AIAA paper no. 2013-0693}, url = {http://arc.aiaa.org/doi/pdfplus/10.2514/6.2013-693}, booktitle = {51st AIAA Aerospace Science Meeting, Grapevine, Texas, USA, Jan. 07-10}, DOI = {10.2514/6.2013-693}, author = {Schimek, S. and G{\"o}ke, S. and Paschereit, C. O.} } @Inproceedings { Nayeri2013a, title = {Experimental challenges of the prediction of the slipstream effect of high speed trains in a wind tunnel with a stationary floor}, year = {2013}, volume = {44}, pages = {9-27}, publisher = {Interdisziplin{\"a}rer Forschungsverbund (IFV) Bahntechnik e.V., Salzufer 17-19, 10587 Berlin, Germany}, series = {Bahntechnik aktuell, Schriftenreihe des Interdisziplin{\"a}ren Forschungsverbundes Bahntechnik e.V.}, booktitle = {2nd international symposium on Rail Aerodynamics, Aerodynamics of Trains and Infrastructure, Berlin, Germany}, ISBN = {978-3-940727-37-4}, ISSN = {1867-240X}, author = {Nayeri, C. N. and Gencaslan, U. and Tietze, A. and Strangfeld, C. and Sieber, M. and Wieser, D. and Weise, M. and Paschereit, C. O.} } @Inproceedings { nawroth2013b, title = {Experimental Investigation of an Unconfined Swirl-Stabilized Turbulent Premixed Flame}, year = {2013}, number = {AIAA paper 2013-2601}, publisher = {American Institute of Aeronautics and Astronautics}, booktitle = {43rd AIAA Fluid Dynamics Conference, June 24-27, 2013, San Diego, California, USA}, ISBN = {978-1-62410-214-1}, DOI = {10.2514/6.2013-2601}, author = {Nawroth, H. and Moriarty, K. and Beuth, J. and Paschereit, C. O.} } @Inproceedings { Schroedinger2013d, title = {Experimental Investigations of the Impact of Equivalence Ratio Oscillations on a Bluff Body Flame}, year = {2013}, number = {paper no. P3-65}, booktitle = {Proceedings of the 6th European Combustion Meeting (ECM) June 25-28, 2013, Lund, Sweden}, ISBN = {978-91-637-2151-9}, author = {Schr{\"o}dinger, C. and Nolte, D. and Oevermann, M. and Paschereit, C. O.} } @Inproceedings { Strangfeld2013a, title = {Experimental Study of Baseline Flow Characteristics for the Realistic Car Model DrivAer}, year = {2013}, number = {SAE Technical Paper 2013-01-1251}, abstract = {The realistic car model DrivAer is investigated experimentally up to a Reynolds number of 2.8 million in the closed-loop wind tunnel at the ''Technische Universit{\"a}t'' Berlin. This new open-source design-hybrid of an ''Audi A4™'' and a ''BMW 3 series™'' possesses more representative car features as the well-known generic ''Ahmed-Body''. Therefore, the study of realistic flow structures is enabled. The main focus of the experimental investigations is the analysis of unsteady flow phenomena in the near wake of the model with a fastback configuration. An internal six component force balance and 63 pressure sensors measured simultaneously the forces and surface pressures with a sample rate of 5kHz. Furthermore, the velocity field in the plane of symmetry is visualized through Particle Image Velocimetry. In the trailing edge region of the roof and the beginning of the rear window a local low pressure peak likely caused by a vortex is detected. This vortex may sustain the flow attachment downstream and hence, improves the pressure recovery. Although instantaneous flow field snapshots illustrate large-scale structures and the meandering of a free stagnation point in the model's wake, no dominant frequencies are found from spectral analysis of time-resolved pressure and force measurements.}, url = {http://papers.sae.org/2013-01-1251/}, publisher = {Society of Automobile Engineers}, booktitle = {SAE 2013 World Congress \& Exhibition, 16. April 2013, Detroit, Michigan, USA}, DOI = {10.4271/2013-01-1251}, author = {Strangfeld, C. and Wieser, D. and Schmidt, H.-J. and Woszidlo, R. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { kabiraj2013a, title = {Experimental Study of Noise Generation by a Turbulent Premixed Flame}, year = {2013}, number = {AIAA paper 2013-2002}, url = {http://arc.aiaa.org/doi/pdf/10.2514/6.2013-2002}, publisher = {American Institute of Aeronautics and Astronautics}, booktitle = {19th AIAA/CEAS Aero-acoustics Conference, May 27-29, 2013, Berlin, Germany}, DOI = {10.2514/6.2013-2002}, author = {Kabiraj, L. and Nawroth, H. and Saurabh, A. and Paschereit, C. O.} } @Inproceedings { Reichel2013e, title = {Experimentelle Untersuchung des Einflusses eines axialen Freistrahls auf drallstabilisierte, mager vorgemischte Wasserstoffflammen}, year = {2013}, pages = {36.1-36.7}, editor = {K{\"a}hler, C. and Hain, R. and Cierpka, C. and Ruck, B. and Leder, A. and Dopheide, D.}, booktitle = {Proceedings der 21. GALA-Fachtagung ''Lasermethoden in der Str{\"o}mungsmesstechnik'', 3.-5. September 2013, Universit{\"a}t der Bundeswehr, M{\"u}nchen, Germany}, ISBN = {978-3-9805613-9-6}, ISSN = {2194-2447}, author = {Reichel, T. G. and Paschereit, C. O.} } @Inproceedings { Reichel2013d, title = {Flow Field Manipulation by Axial Air Injection to Achieve Flashback Resistance and its Impact on Mixing Quality}, year = {2013}, number = {AIAA paper no. 2013-2603}, url = {http://arc.aiaa.org/doi/pdfplus/10.2514/6.2013-2603}, booktitle = {51st AIAA Aerospace Science Meeting, Grapevine, Texas, USA, Jan. 07-10}, DOI = {10.2514/6.2013-2603}, author = {Reichel, T. G. and Terhaar, S. and Paschereit, C. O.} } @Inproceedings { nawroth2013c, title = {Flow Investigation and Acoustic Measurements of an Unconfined Turbulent Premixed Jet Flame}, year = {2013}, number = {AIAA paper 2013-2459}, publisher = {American Institute of Aeronautics and Astronautics}, booktitle = {43rd AIAA Fluid Dynamics Conference, June 24-27, 2013, San Diego, California, USA}, ISBN = {978-1-62410-214-1}, DOI = {10.2514/6.2013-2459}, author = {Nawroth, H. and Paschereit, C. O. and Zhang, F. and Habisreuther, P. and Bockhorn, H.} } @Inproceedings { Terhaar2013, title = {Impact of Shear Flow Instabilities on the Magnitude and Saturation of the Flame Response}, year = {2013}, number = {ASME paper GT2013-95729}, pages = {V01BT04A056 (13 pages)}, booktitle = {Proc. ASME Turbo Expo 2013, June 3-7, San Antonio, Texas, USA}, ISBN = {978-0-7918-5511-9}, DOI = {10.1115/GT2013-95729}, author = {Terhaar, S. and \'{C}osi\'{c}, B. and Oberleithner, K. and Paschereit, C. O.} } @Inproceedings { Holst2013, title = {Influence of a Finite Width Micro-Tab on the Spanwise Lift Distribution}, year = {2013}, number = {ASME paper GT2013-94381}, pages = {V008T44A011 (10 pages)}, booktitle = {Proc. ASME Turbo Expo 2013, June 3-7, San Antonio, Texas, USA}, ISBN = {978-0-7918-5529-4}, DOI = {10.1115/GT2013-94381}, author = {Holst, D. and Bach, A. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Cosic2012d, title = {Influence of pressure and steam dilution on NOx and CO emissions in a premixed natural gas flame}, year = {2013}, number = {ASME paper GT2013-94782}, pages = {V01AT04A056 (11 pages)}, booktitle = {Proc. ASME Turbo Expo 2013, June 3-7, San Antonio, Texas, USA}, ISBN = {978-0-7918-5510-2}, DOI = {10.1115/GT2013-94782}, author = {G{\"o}ke, S. and Schimek, S. and Terhaar, S. and Reichel, T. G. and G{\"o}ckeler, K. and Kr{\"u}ger, O. and Fleck, J. and Griebel, P. and Paschereit, C. O.} } @Inproceedings { kabiraj2013c, title = {Instabilities in a Confined Flat-flame System}, year = {2013}, number = {P2-30}, pages = {6 pages}, booktitle = {Proceedings of the 6th European Combustion Meeting (ECM), June 25-28, 2013, Lund, Sweden}, ISBN = {978-91-637-2151-9}, author = {Kabiraj, L. and Saurabh, A. and Steinert, R. and Paschereit, C. O.} } @Inproceedings { Kruger2013a, title = {Large Eddy Simulations of Methane Oxidation at Ultra-Wet Conditions in a Model Gas Turbine Combustor Applying Detailed Chemistry}, year = {2013}, pages = {1--6}, publisher = {Japan Society of Mechanical Engineers}, booktitle = {Proceedings of 4th International Conference on Jets, Wakes and Separated Flows (ICJWSF), Sep 17-21, 2013, Nagoya, Aichi, Japan}, ISBN = {978-4-88898-234-4 (CD)}, author = {Kr{\"u}ger, O. and Duwig, C. and Terhaar, S. and Paschereit, C. O.} } @Inproceedings { Kruger2013b, title = {Numerical Investigations and Modal Analysis of the Coherent Structures in a Generic Swirl Burner}, year = {2013}, number = {AIAA paper 2013-2953}, pages = {1--16}, url = {http://arc.aiaa.org/doi/abs/10.2514/6.2013-2953}, publisher = {American Institute of Aeronautics and Astronautics}, booktitle = {21th AIAA Computational Fluid Dynamics Conference, June 24-27, 2013, San Diego, California, USA}, DOI = {10.2514/6.2013-2953}, author = {Kr{\"u}ger, O. and Duwig, C. and Terhaar, S. and Paschereit, C. O.} } @Inproceedings { Schroedinger2013c, title = {Numerical Investigations of the Impact of Temperature Fluctuations on Lean Premixed Flames}, year = {2013}, booktitle = {Proceedings of the 24th International Colloquium on the Dynamics of Explosions and Reactive Systems (ICDERS) 28 July - 2 August 2013, Taipei, Taiwan (Republic of China)}, author = {Schr{\"o}dinger, C. and Oevermann, M. and Paschereit, C. O.} } @Inproceedings { Bobusch2013b, title = {Numerical Investigations on Geometric Parameters Affecting the Oscillation Properties of a Fluidic Oscillator}, year = {2013}, number = {AIAA paper 2013-2953}, pages = {1--15}, keywords = {a parametric study of,active flow control actuator,cfd,flow control actuators,fludic oscillator,fluid dynamics,fluidic oscillators are gaining,interest as novel active,modeling and simulation,numerical model to perform,parameter study,subject,the current,the internal,work utilizes a validated}, url = {http://arc.aiaa.org/doi/abs/10.2514/6.2013-2709}, publisher = {American Institute of Aeronautics and Astronautics}, booktitle = {21th AIAA Computational Fluid Dynamics Conference, June 24-27, 2013, San Diego, California, USA}, DOI = {10.2514/6.2013-2709}, author = {Bobusch, B. and Woszidlo, R. and Kr{\"u}ger, O. and Paschereit, C. O.} } @Inproceedings { Kruger2013, title = {Numerical Modeling and Validation of the Flow in a Fluidic Oscillator}, year = {2013}, number = {AIAA paper 2013-3087}, pages = {1--13}, url = {http://arc.aiaa.org/doi/abs/10.2514/6.2013-3087}, publisher = {American Institute of Aeronautics and Astronautics}, booktitle = {21th AIAA Computational Fluid Dynamics Conference, June 24-27, 2013, San Diego, California, USA}, DOI = {10.2514/6.2013-3087}, author = {Kr{\"u}ger, O. and Bobusch, B. and Woszidlo, R. and Paschereit, C. O.} } @Inproceedings { Bobusch2013c, title = {Optical Measurement of Local and Global Transfer Functions for Equivalence Ratio Fluctuations in a Turbulent Swirl Flame}, year = {2013}, number = {ASME paper GT2013-95649}, pages = {V01BT04A048 (12 pages)}, booktitle = {Proc. ASME Turbo Expo 2013, June 3-7, San Antonio, Texas, USA}, ISBN = {978-0-7918-5511-9}, DOI = {10.1115/GT2013-95649}, author = {Bobusch, B. and \'{C}osi\'{c}, B. and Moeck, J. P. and Paschereit, C. O.} } @Inproceedings { Cosic2013e, title = {Prediction of Pressure Amplitudes of Self-Excited Thermoacoustic Instabilities for a Partially Premixed Swirl-Flame}, year = {2013}, number = {ASME paper GT2013-94160}, pages = {V01AT04A007 (11 pages)}, booktitle = {Proc. ASME Turbo Expo 2013, June 3-7, San Antonio, Texas, USA}, ISBN = {978-0-7918-5510-2}, DOI = {10.1115/GT2013-94160}, author = {\'{C}osi\'{c}, B. and Moeck, J. P. and Paschereit, C. O.} } @Inproceedings { Marten2013, title = {QBlade: An Open Source Tool for Design and Simulation of Horizontal and vertical Axis Wind Turbines}, journal = {International Journal of Emerging Technology and Advanced Engineering, vol. 3, special issue 3}, year = {2013}, url = {http://www.ijetae.com/files/Conference\%20ICERTSD-2013/IJETAE_ICERTSD_0213_41.pdf}, booktitle = {International Conference on Energy Resources and Technologies for Sustainable Development (ICERTSD), Bengal Engineering \& Science University, Shibpur, Howrah, West Bengal, INDIA}, ISSN = {ISSN 2250 - 2459 (Online)}, author = {Marten, D. and Wendler, J. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Goeckeler2013a, title = {Residence Time Distribution in a Swirling Flow at Non-Reacting, Reacting, and Steam-Diluted Conditions}, year = {2013}, volume = {Volume 1B: Combustion, Fuels and Emissions}, number = {ASME paper GT2013-95594}, pages = {V01BT04A047 (12 pages)}, booktitle = {Proc. ASME Turbo Expo 2013, June 3-7, San Antonio, Texas, USA}, ISBN = {978-0-7918-5511-9}, DOI = {10.1115/GT2013-95594}, author = {G{\"o}ckeler, K. and Terhaar, S. and Paschereit, C. O.} } @Inproceedings { saurabh2013d, title = {Swirl Flame Interaction with Transverse and Axial Acoustic Forcing}, year = {2013}, pages = {1--6}, booktitle = {Proceedings of 4th International Conference on Jets, Wakes and Separated Flows (ICJWSF), Sep 17-21, 2013, Nagoya, Aichi, Japan}, ISBN = {978-4-88898-234-4 (CD)}, author = {Saurabh, A. and Paschereit, C. O.} } @Inproceedings { Vahl2013, title = {Thick Airfoil Deep Dynamic Stall and its Control}, year = {2013}, number = {AIAA paper no. 2013-0854}, url = {http://arc.aiaa.org/doi/pdfplus/10.2514/6.2013-693}, booktitle = {51st AIAA Aerospace Science Meeting, Grapevine, Texas, USA, Jan. 07-10}, DOI = {10.2514/6.2013-854}, author = {Mueller-Vahl, H. and Strangfeld, C. and Nayeri, C. N. and Paschereit, C. O. and Greenblatt, D.} } @Inproceedings { Bach2013, title = {Transitional Effects of Active Micro-Tabs for Wind Turbine Load Control}, year = {2013}, number = {ASME paper GT2013-94369}, pages = {V008T44A010 (8 pages)}, booktitle = {Proc. ASME Turbo Expo 2013, June 3-7, San Antonio, Texas, USA}, ISBN = {978-0-7918-5529-4}, DOI = {10.1115/GT2013-94369}, author = {Bach, A. and Holst, D. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { TerhaarBP2013, title = {Untersuchung einer drallstabilisierten Freistrahlflamme mit azimutaler Anregung}, year = {2013}, pages = {37.1-37.8}, editor = {K{\"a}hler, C. and Hain, R. and Cierpka, C. and Ruck, B. and Leder, A. and Dopheide, D.}, booktitle = {Proceedings der 21. GALA-Fachtagung ''Lasermethoden in der Str{\"o}mungsmesstechnik'', 3.-5. September 2013, Universit{\"a}t der Bundeswehr, M{\"u}nchen, Germany}, ISBN = {978-3-9805613-9-6 (print)}, ISSN = {2194-2447}, author = {Terhaar, S. and Beuth, J. and Paschereit, C. O.} } @Inproceedings { Terhaar2013a, title = {Vortex Breakdown and Global Modes in Swirling Combustor Flows with Axial Air Injection}, year = {2013}, pages = {1--16}, url = {http://arc.aiaa.org/doi/pdfplus/10.2514/6.2013-2602}, booktitle = {Proceedings of 43st AIAA Fluid Dynamics Conference and Exhibit, June 24-27 2013, San Diego, CA, USA}, DOI = {10.2514/6.2013-2602}, author = {Terhaar, S. and Reichel, T. G. and Schr{\"o}dinger, C. and Rukes, L. and Oberleithner, K. and Paschereit, C. O.} } @Inproceedings { Oberleithner2013, title = {Why Non-Uniform Density Suppress the Precessing Vortex Core}, year = {2013}, number = {ASME paper GT2013-95509}, pages = {V01BT04A041 (12 pages)}, booktitle = {Proc. ASME Turbo Expo 2013, June 3-7, San Antonio, Texas, USA}, ISBN = {978-0-7918-5511-9}, DOI = {10.1115/GT2013-95509}, author = {Oberleithner, K. and Terhaar, S. and Rukes, L. and Paschereit, C. O.} } @Inproceedings { Nayeri2013c, title = {Wind tunnel experiments on the control of the lee side vortex of high-speed trains}, year = {2013}, pages = {1--6}, web_url = {nayeri_ICJWSF_2013.pdf}, publisher = {Japan Society of Mechanical Engineers}, booktitle = {Proceedings of 4th International Conference on Jets, Wakes and Separated Flows (ICJWSF), Sep 17-21, 2013, Nagoya, Aichi, Japan}, ISBN = {978-4-88898-234-4 (CD)}, author = {Nayeri, C. N. and Neumann, U. and Tschepe, J. and Strangfeld, C. and Wieser, D. and Paschereit, C. O.} } @Article { TerhaarBP2012_2, title = {Effects of Outlet Boundary Conditions on the Reacting Flow Field in a Swirl-Stabilized Burner at Dry and Humid Conditions}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2012}, month = {9}, day = {20}, volume = {134}, number = {11}, pages = {111501}, ISSN = {0742-4795 (online), 1528-8919 (print)}, DOI = {10.1115/1.4007165}, author = {Terhaar, S. and Bobusch, B. and Paschereit, C. O.} } @Article { Cosic2012c, title = {Acoustic Response of a Helmholtz Resonator Exposed to Hot-Gas Penetration and High Amplitude Oscillations}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2012}, month = {8}, day = {22}, volume = {134}, number = {10}, pages = {101503}, url = {http://link.aip.org/link/?GTP/134/101503/1}, publisher = {ASME}, ISSN = {0742-4795 (online), 1528-8919 (print)}, DOI = {10.1115/1.4007024}, author = {\'{C}osi\'{c}, B. and Reichel, T. G. and Paschereit, C. O.} } @Article { Krediet2012a, title = {Identification of the Flame Describing Function of a Premixed Swirl Flame from LES}, journal = {Combustion Science and Technology}, year = {2012}, month = {7}, volume = {184}, number = {7-8}, pages = {888--900}, abstract = {Thermo-acoustic characterization of gas turbine combustion systems is crucial for a successful development of new gas turbine engines to meet emission and efficiency targets. In this context, it becomes more and more necessary to predict the limit cycle amplitudes of thermo-acoustic induced combustion instabilities in order to figure out if they can be tolerated or if they are above the critical design limit and will cause damage to the engine. For the prediction of limit cycle amplitudes, the nonlinear flame response of the combustion system is needed, which is represented in this work by the flame describing function (FDF). In this article, the identification of the FDF from a large eddy simulation (LES) is validated. The test case used was a premixed atmospheric swirl flame, for which experimental data on the FDF were available. First a steady reacting LES solution was obtained and compared to experimental data. The simulation was then excited by superimposing a mono-frequency harmonic wave on the velocity inlet boundary condition. Both the frequency and amplitude of the acoustic wave were varied to obtain the FDF. The calculated FDF was in good agreement with experimental data. At a frequency of 115 Hz, the heat release rate of the flame was found to saturate for larger excitation amplitudes.}, url = {http://www.mendeley.com/research/identification-flame-describing-function-premixed-swirl-flame-les/}, ISSN = {0010-2202}, DOI = {10.1080/00102202.2012.663981}, author = {Krediet, H. J. and Beck, C. H. and Krebs, W. and Schimek, S. and Paschereit, C. O. and Kok, J. B. W.} } @Article { cosic:2012, title = {Open-Loop Control of Combustion Instabilities and the Role of the Flame Response to Two-Frequency Forcing}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2012}, month = {4}, day = {12}, volume = {134}, number = {6}, pages = {061502}, url = {http://link.aip.org/link/?GTP/134/061502/1}, publisher = {ASME}, ISSN = {0742-4795 (online), 1528-8919 (print)}, DOI = {10.1115/1.4005986}, author = {\'{C}osi\'{c}, B. and Bobusch, B. and Moeck, J. P. and Paschereit, C. O.} } @Article { Gelbert2012, title = {Advanced algorithms for gradient estimation in one- and two-parameter extremum seeking controllers}, journal = {Journal of Process Control}, year = {2012}, volume = {22}, number = {4}, pages = {700-709}, abstract = {In extremum seeking control, the gradient estimation is the key enabler for a successful online optimization. For this purpose, the classical algorithm uses a combination of high- and low-pass filters. In this investigation extended Kalman filters (EKF) are used instead. The approach is explained in detail and advantages of Kalman filtering will become apparent. A novel approach for the gradient estimation for dual-input single-output systems is presented. The proposed EKF incorporates the coupling of the output to both inputs, thus, enabling a superior gradient estimate. A simulation study shows that faster convergence of the extremum-seeking controller can be achieved using this estimator. The feasibility of the proposed algorithm in an experimental setup is demonstrated by control of thermoacoustic instabilities in an atmospheric combustor test rig.}, url = {http://www.sciencedirect.com/science/article/pii/S0959152412000340}, ISSN = {0959-1524}, DOI = {10.1016/j.jprocont.2012.01.022}, author = {Gelbert, G. and Moeck, J. P. and Paschereit, C. O. and King, R.} } @Article { Winkler2012, title = {Aeroacoustic Effects of a Cylinder-Plate Configuration}, journal = {AIAA Journal}, year = {2012}, volume = {50}, number = {7}, pages = {1614--1620}, DOI = {10.2514/1.J051578}, author = {Winkler, M. and Becker, K. and Doolan, C. and Kameier, F. and Paschereit, C. O.} } @Article { Gelbert2012a, title = {Feedback control of unstable thermoacoustic modes in an annular Rijke tube}, journal = {Control Engineering Practice}, year = {2012}, volume = {20}, number = {8}, pages = {770-782}, abstract = {Simulation and experimental results from an annular Rijke tube are presented. This system is a thermoacoustic surrogate system of an annular gas turbine combustor which, despite its simplicity, possesses the basic mechanisms to feature unstable azimuthal modes. A thermoacoustic network model is set up and used to derive low-order models for modal control of the system. The derived controllers are successfully applied in simulation and experiment. With the modal controllers, all unstable acoustic modes can be eliminated individually. A simultaneous use of all controllers results in a complete stabilization of the system.}, url = {http://www.sciencedirect.com/science/article/pii/S0967066112000809}, ISSN = {0967-0661}, DOI = {10.1016/j.conengprac.2012.03.016}, author = {Gelbert, G. and Moeck, J. P. and Paschereit, C. O. and King, R.} } @Article { Oberleithner2012a, title = {Formation of Turbulent Vortex Breakdown: Intermittency, Criticality, and Global Instability}, journal = {AIAA Journal}, year = {2012}, volume = {50}, number = {7}, pages = {1437-1452}, DOI = {10.2514/1.J050642}, author = {Oberleithner, K. and Seele, R. and Paschereit, C. O. and Wygnanski, I.} } @Article { lacarelle2012, title = {Increasing the Passive Scalar Mixing Quality of Jets in Crossflow With Fluidics Actuators}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2012}, volume = {134}, number = {2}, pages = {021503 (7 pages)}, abstract = {Jets in crossflow are widely used in the industry for homogenization or cooling tasks.Recently, pulsating jets have been investigated as a mean to increase the scalar mixingefficiency of such configurations, whether for a single jet or for an array of jets. To avoidthe disadvantages of mechanically actuated flows (costs, maintenance), a new injectorbased on a fluidics oscillator has been designed. Four injectors have been implementedin a generical jet in crossflow configuration and the mixing efficiency of the setup wascompared with the one of the same setup equiped with standard non oscillating jets. Withhelp of high-speed concentration measurement technique, the scalar mixing quality ofboth setups was measured at three positions downstream of the injection plane. In all thecases tested, the fluidics injectors present a better temporal homogenization, characterized by the Danckwerts unmixedness criterion, than the standard jets. For a defined mixing quality, a decrease of the mixing length by approximately 50\% can be achieved with the fluidics injectors. Furthermore, the new injectors exhibit a mixing quality which isless sensitive to variations of the jet to crossflow momentum. The flapping motion of thefluidics injectors induces a wider azimuthal spreading of the fluidics jets immediatelydownstream of the injection location. This increases the macro- and micro-mixing phenomea which lead then to the high gains in mixing quality. It is thus demonstrated that fluidics oscillators present a strong potential to improve the passive scalar homogenization of jet in crossflow configurations.}, url = {http://link.aip.org/link/?GTP/134/021503/1}, publisher = {ASME}, ISSN = {0742-4795 (online), 1528-8919 (print)}, DOI = {10.1115/1.4004373}, author = {Lacarelle, A. and Paschereit, C. O.} } @Article { Goeke2012d, title = {Influence of Steam Dilution on NOx Formation in Premixed Methane / Hydrogen Flames}, journal = {Journal of Propulsion and Power}, year = {2012}, publisher = {American Institute of Aeronautics and Astronautics}, ISSN = {0748-4658, EISSN: 1533-3876}, DOI = {10.2514/1.B34577}, author = {G{\"o}ke, S. and Paschereit, C. O.} } @Article { Moeck2012, title = {Nonlinear interactions of multiple linearly unstable thermoacoustic modes}, journal = {International journal of spray and combustion dynamics}, year = {2012}, volume = {4}, number = {1}, pages = {1-28}, abstract = {We investigate the dynamics of thermoacoustic systems with multiple linearly unstable modes. Ifa linear analysis reveals more than one mode with positive growth rate, nonlinear methods haveto be used to determine the existence and stability of steady-state oscillations. One possible wayto engage this problem is a first-order harmonic balance approach based on describing functionrepresentations for the flame response. In contrast to the case of a single unstable mode, thenonlinearity output to multiple sinusoidal components with different frequencies and amplitudeshas to be known. Based on this approach, we present conditions for the existence and stability ofsingle- or multi-mode steady-state oscillations. We apply this method to a thermoacoustic modelsystem having two linearly unstable modes. By varying one of the system parameters, we findstable and unstable single-mode steady-states as well as unstable simultaneous oscillations.Associated with the stability of the single-mode limit cycles, we identify hysteresis in theoscillation type. Some related experimental observations are discussed.}, publisher = {Multi-Science Publishing}, ISSN = {1756-8277}, author = {Moeck, J. P. and Paschereit, C. O.} } @Article { Candel2012, title = {Progress and challenges in swirling flame dynamics}, journal = {Comptes Rendus M{\'e}canique}, year = {2012}, volume = {340}, number = {11--12}, pages = {758--768}, url = {http://www.sciencedirect.com/science/article/pii/S163107211200188X}, ISSN = {1631-0721}, DOI = {10.1016/j.crme.2012.10.024}, author = {Candel, S. and Durox, D. and Schuller, T. S. and Palies, P. and Bourgouin, J.-F. and Moeck, J. P.} } @Article { Schneider:2012, title = {Spannungsoptik-Tomographie zur Messung der Scherung in Str{\"o}mungen}, journal = {tm - Technisches Messen}, year = {2012}, volume = {79}, number = {6}, pages = {304--309}, url = {http://www.oldenbourg-link.com/doi/abs/10.1524/teme.2012.0211}, publisher = {Oldenbourg Wissenschaftsverlag GmbH}, ISSN = {0171-8096}, DOI = {10.1524/teme.2012.0211}, author = {Schneider, T. and Goubergrits, L. and Paschereit, C. O. and Kertzscher, U. and Affeld, K.} } @Conference { Pechlivanoglou2012, title = {Active stall control solutions for power regulation and load alleviation of large wind turbines}, year = {2012}, booktitle = {Conference on Modelling Fluid Flow, The 15th International Conference on Fluid Flow Technologies, Budapest, Hungary, 4-7 Sep.}, author = {Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.} } @Conference { Sieber2012, title = {Experimental investigations of a transient swirling jet}, year = {2012}, url = {http://www.efmc9.eu/absbook/files/0519_SH3_Sieber_Moritz.pdf}, booktitle = {9th European Fluid Mechanics Conference, University of Rome ''Tor Vergata'', Italy, 9-13 September}, author = {Sieber, M. and Rukes, L. and Oberleithner, K. and Nayeri, C. N. and Paschereit, C. O.} } @Conference { Wendler2012, title = {QBlade: OpenSource Horizontal and Vertical Axis Wind turbine Design and Simulation}, year = {2012}, web_url = {QBlade_poster.pdf}, booktitle = {Renewable Energy 2030 - Experts Visions, Carl von Ossietzky University, Oldenburg, Germany, 1-2 Oct.}, author = {Wendler, J. and Marten, D. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.} } @Conference { Rukes2012, title = {Stability characteristics of swirling jet flow transients}, year = {2012}, url = {http://www.efmc9.eu/absbook/files/0242_IN11_Rukes_Lothar.pdf}, booktitle = {9th European Fluid Mechanics Conference, University of Rome ''Tor Vergata'', Italy, 9-13 September}, author = {Rukes, L. and Oberleithner, K. and Sieber, M. and Nayeri, C. N. and Paschereit, C. O.} } @Conference { Vahl2012b, title = {Thick airfoil deep dynamic stall}, year = {2012}, booktitle = {EUROMECH Colloquium 528 - Wind Energy and the impact of turbulence on the conversion process, Oldenburg, Germany, 22-24 Feb.}, author = {Mueller-Vahl, H. and Strangfeld, C. and Nayeri, C. N. and Paschereit, C. O. and Greenblatt, D.} } @Inproceedings { Cosic2012b, title = {Acoustic response of a Helmholtz resonator exposed to hot-gas penetration and high amplitude oscillations}, year = {2012}, number = {ASME paper GT2012-69033}, pages = {767-779 (13 pages)}, booktitle = {Proc. ASME Turbo Expo 2012, June 11-15, Bella Center, Copenhagen, Denmark}, ISBN = {978-0-7918-4468-7}, DOI = {10.1115/GT2012-69033}, author = {\'{C}osi\'{c}, B. and Reichel, T. G. and Paschereit, C. O.} } @Inproceedings { Schimek2012c, title = {Amplitude-dependent flow field and flame response to axial and tangential velocity fluctuations}, year = {2012}, number = {ASME paper GT2012-69785}, pages = {1321-1333 (13 pages)}, booktitle = {Proc. ASME Turbo Expo 2012, June 11-15, Bella Center, Copenhagen, Denmark}, ISBN = {978-0-7918-4468-7}, DOI = {10.1115/GT2012-69785}, author = {Schimek, S. and \'{C}osi\'{c}, B. and Moeck, J. P. and Terhaar, S. and Paschereit, C. O.} } @Inproceedings { schimek2012, title = {Analysis of flame transfer functions for blends of CH4 and H2 at different humidity levels}, year = {2012}, number = {AIAA paper no. 2012-0932}, url = {http://arc.aiaa.org/doi/pdfplus/10.2514/6.2012-932}, booktitle = {50th AIAA Aerospace Science Meeting, Nashville, Tennessee, USA, Jan. 9-12}, DOI = {10.2514/6.2012-932}, author = {Schimek, S. and G{\"o}ke, S. and Schr{\"o}dinger, C. and Paschereit, C. O.} } @Inproceedings { Krebs2012, title = {Comparison of nonlinear to linear thermoacoustic stability analysis of a gas turbine combustion system}, year = {2012}, number = {ASME paper GT2012-69477}, pages = {1113-1124 (12 pages)}, booktitle = {Proc. ASME Turbo Expo 2012, June 11-15, Bella Center, Copenhagen, Denmark}, ISBN = {978-0-7918-4468-7}, DOI = {10.1115/GT2012-69477}, author = {Krebs, W. and Krediet, H. and Hermeth, S. and Poinsot, T. E. P. and Schimek, S. and Paschereit, C. O.} } @Inproceedings { TerhaarBP2012, title = {Effects of Outlet Boundary Conditions on the Reacting Flow Field in a Swirl-Stabilized Burner at Dry and Humid Conditions}, year = {2012}, pages = {1295-1306 (12 pages)}, booktitle = {Proc. ASME Turbo Expo 2012, June 11-15, Bella Center, Copenhagen, Denmark , ASME paper GT2012-69753}, ISBN = {978-0-7918-4468-7}, DOI = {10.1115/GT2012-69753}, author = {Terhaar, S. and Bobusch, B. and Paschereit, C. O.} } @Inproceedings { nawroth2012a, title = {Experimental and Numerical Investigation of a Turbulent Premixed Flame in an Anechoic Environment}, year = {2012}, number = {AIAA paper 2012-3072}, url = {http://arc.aiaa.org/doi/abs/10.2514/6.2012-3072}, publisher = {American Institute of Aeronautics and Astronautics}, booktitle = {42nd AIAA Fluid Dynamics Conference, June 25-28, 2012, New Orleans, Louisiana, USA}, DOI = {10.2514/6.2012-3072}, author = {Nawroth, H. and Saurabh, A. and Paschereit, C. O. and Zhang, F. and Habisreuther, P. and Bockhorn, H.} } @Inproceedings { Schimek2012b, title = {Flame transfer function measurements with CH4 and H2 fuel mixtures at ultra wet conditions in a swirl stabilized premixed combustor}, year = {2012}, number = {ASME paper GT2012-69788}, pages = {1335-1344 (10 pages)}, booktitle = {Proc. ASME Turbo Expo 2012, June 11-15, Bella Center, Copenhagen, Denmark}, ISBN = {978-0-7918-4468-7}, DOI = {10.1115/GT2012-69788}, author = {Schimek, S. and G{\"o}ke, S. and Schr{\"o}dinger, C. and Paschereit, C. O.} } @Inproceedings { TerhaarP2012, title = {High-Speed PIV Investigation of Coherent Structures in a Swirl-Stabilized Combustor Operating at Dry and Steam-Diluted Conditions}, year = {2012}, url = {http://ltces.dem.ist.utl.pt/lxlaser/lxlaser2012/upload/212_paper_bysdxt.pdf}, booktitle = {16th Int Symp on Applications of Laser Techniques to Fluid Mechanics Lisbon, Portugal, 09-12 July, 2012}, author = {Terhaar, S. and Paschereit, C. O.} } @Inproceedings { Goeke2012, title = {Influence of Steam Dilution on NOx Formation in Premixed Natural Gas and Hydrogen Flames}, year = {2012}, number = {AIAA paper no. 2012-1272}, url = {http://arc.aiaa.org/doi/pdfplus/10.2514/6.2012-1272}, booktitle = {50th AIAA Aerospace Science Meeting, Nashville, Tennessee, USA, Jan. 9-12}, DOI = {10.2514/6.2012-1272}, author = {G{\"o}ke, S. and Paschereit, C. O.} } @Inproceedings { Goeke2012a, title = {Influence of Steam Dilution on the Combustion of Natural Gas and Hydrogen in Premixed and Rich-Quench-Lean Combustors}, year = {2012}, booktitle = {The Eleventh International Conference on Combustion and Energy Utilization (11th ICCEU)}, author = {G{\"o}ke, S. and F{\"u}ri, M. and Bourque, G. and G{\"o}ckeler, K. and Kr{\"u}ger, O. and Bobusch, B. and Schimek, S. and Terhaar, S. and Paschereit, C. O.} } @Inproceedings { Kruger2012, title = {Large Eddy Simulations of Hydrogen Oxidation at Ultra-wet Conditions in a Model Gas Turbine Combustor Applying Detailed Chemistry}, year = {2012}, number = {ASME paper GT2012-69446}, pages = {1081-1094 (14 pages)}, booktitle = {Proc. ASME Turbo Expo 2012, June 11-15, Bella Center, Copenhagen, Denmark}, ISBN = {978-0-7918-4468-7}, DOI = {10.1115/GT2012-69446}, author = {Kr{\"u}ger, O. and Duwig, C. and Terhaar, S. and Paschereit, C. O.} } @Inproceedings { Albin2012, title = {Measurement and Simulation of burning velocities of ultra-wet methane-air-steam mixtures}, year = {2012}, booktitle = {The Eleventh International Conference on Combustion and Energy Utilization (11th ICCEU)}, author = {Albin, E. and Nawroth, H. and G{\"o}ke, S. and D'Angelo, Y. and Paschereit, C. O.} } @Inproceedings { Schuller2012, title = {Modeling the response of premixed flame transfer functions -- Key elements and experimental proofs}, year = {2012}, number = {AIAA paper no. 2012-0985}, url = {http://arc.aiaa.org/doi/pdfplus/10.2514/6.2012-985}, booktitle = {50th AIAA Aerospace Science Meeting, Nashville, Tennessee, USA, Jan. 9-12}, DOI = {10.2514/6.2012-985}, author = {Schuller, T. S. and Cuquel, A. and Palies, P. and Moeck, J. P. and Durox, D. and Candel, S.} } @Inproceedings { Schroedinger2012, title = {Numerical studies on the impact of equivalence ratio oscillations on lean premixed flame characteristics and emissions}, year = {2012}, url = {http://www.iccfd.org/iccfd7/assets/pdf/papers/ICCFD7-3401_paper.pdf}, booktitle = {Seventh International Conference on Computational Fluid Dynamics (ICCFD7), Big Island, Hawaii, July 9-13}, author = {Schr{\"o}dinger, C. and Paschereit, C. O. and Oevermann, M.} } @Inproceedings { Schroedinger2012b, title = {Numerical studies on the influence of periodical flow forcing on mixing quality and flow structure of a swirl burner}, year = {2012}, number = {ASME paper GT2012-69843}, pages = {1345--1356 (12 pages)}, booktitle = {Proc. ASME Turbo Expo 2012, June 11-15, Bella Center, Copenhagen, Denmark}, ISBN = {978-0-7918-4468-7}, DOI = {10.1115/GT2012-69843}, author = {Schr{\"o}dinger, C. and Moeck, J. P. and Oevermann, M. and Paschereit, C. O.} } @Inproceedings { Vey2012, title = {On the Frequency Scaling of the Forced Flow Above a Low Aspect Ratio Wing}, year = {2012}, number = {AIAA paper no. 2012-317}, url = {http://arc.aiaa.org/doi/pdfplus/10.2514/6.2012-317}, booktitle = {50th AIAA Aerospace Science Meeting, Nashville, Tennessee, USA, Jan. 9-12}, DOI = {10.2514/6.2012-317}, author = {Vey, S. and Nayeri, C. N. and Paschereit, C. O. and Greenblatt, D.} } @Inproceedings { Oberleithner2012, title = {On the impact of shear flow instabilities on global heat release rate fluctuations: Linear stability analysis of an isothermal and a reacting swirling jet}, year = {2012}, number = {ASME paper GT2012-69774}, pages = {1307-1320 (14 pages)}, booktitle = {Proc. ASME Turbo Expo 2012, June 11-15, Bella Center, Copenhagen, Denmark}, ISBN = {978-0-7918-4468-7}, DOI = {10.1115/GT2012-69774}, author = {Oberleithner, K. and Schimek, S. and Paschereit, C. O.} } @Inproceedings { Weinzierl2012, title = {Performance Optimization of Wind Turbine Rotors With Active Flow Control: Part 2 -- Active Aeroelastic Simulations}, year = {2012}, number = {ASME paper GT2012-69200}, pages = {915-927 (13 pages)}, booktitle = {Proc. ASME Turbo Expo 2012, June 11-15, Bella Center, Copenhagen, Denmark}, ISBN = {978-0-7918-4472-4}, DOI = {10.1115/GT2012-69200}, author = {Weinzierl, G. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Bobusch2012, title = {Thermoacoustic stability analysis of a kerosene-fueled lean direct injection combustor employing acoustically and optically measured transfer matrices}, year = {2012}, number = {ASME paper GT2012-69034}, pages = {781-794 (14 pages)}, booktitle = {Proc. ASME Turbo Expo 2012, June 11-15, Bella Center, Copenhagen, Denmark}, ISBN = {978-0-7918-4468-7}, DOI = {10.1115/GT2012-69034}, author = {Bobusch, B. and Moeck, J. P. and Sadig, S. and Paschereit, C. O.} } @Inproceedings { Goeke2012c, title = {Ultra-wet Combustion For High Efficiency, Low Emission Gas Turbines}, year = {2012}, pages = {Paper ID Number: 17}, web_url = {Goeke2012c.pdf}, booktitle = {European Turbine Network ETN: The Future of Gas Turbine Technology, 6th IGTC, Brussels, Belgium, Oct. 17-18}, author = {G{\"o}ke, S. and Albin, E. and G{\"o}ckeler, K. and Kr{\"u}ger, O. and Schimek, S. and Terhaar, S. and Paschereit, C. O.} } @Inproceedings { Krueger2012, title = {Ultra-Wet Operation of a Hydrogen Fueled GT Combustor: Large Eddy Simulation Employing Detailed Chemistry}, year = {2012}, url = {http://www.iccfd.org/iccfd7/assets/pdf/papers/ICCFD7-3403_paper.pdf}, booktitle = {Seventh International Conference on Computational Fluid Dynamics (ICCFD7), Big Island, Hawaii, July 9-13}, author = {Kr{\"u}ger, O. and Duwig, C. and Terhaar, S. and Paschereit, C. O.} } @Inproceedings { Vahl2012, title = {Vortex generators for wind turbine blades: a combined wind tunnel and wind turbine parametric study}, year = {2012}, number = {ASME paper GT2012-69197}, pages = {899-914 (16 pages)}, booktitle = {Proc. ASME Turbo Expo 2012, June 11-15, Bella Center, Copenhagen, Denmark}, ISBN = {978-0-7918-4472-4}, DOI = {10.1115/GT2012-69197}, author = {Mueller-Vahl, H. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.} } @Article { schimek2011, title = {An Experimental Investigation of the Nonlinear Response of an Atmospheric Swirl-Stabilized Premixed Flame}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2011}, month = {4}, day = {25}, volume = {133}, number = {10}, pages = {101502 (7 pages)}, abstract = {Due to stringent emission restrictions, modern gas turbines mostly rely on lean premixed combustion. Since this combustion mode is susceptible to thermoacoustic instabilities, there is a need for modeling tools with predictive capabilities. Linear network models are able to predict the occurrence of thermoacoustic instabilities but yield no information on the oscillation amplitude. The prediction of the pulsation levels and hence an estimation whether a certain operating condition has to be avoided is only possible if information on the nonlinear flame response is available. Typically, the flame response shows saturation at high forcing amplitudes. A newly constructed atmospheric test rig, specifically designed for the realization of high excitation amplitudes over a broad frequency range, is used to generate extremely high acoustic forcing power with velocity fluctuations of up to 100\% of the mean flow. The test rig consists of a generic combustor with a premixed swirl-stabilized natural gas flame, where the upstream part has a variable length to generate adaptive resonances of the acoustic field. The OH* chemiluminescence response, with respect to velocity fluctuations at the burner, is measured for various excitation frequencies and amplitudes. From these measurements, an amplitude dependent flame transfer function is obtained. Phase-averaged OH* pictures are used to identify changes in the flame shape related to saturation mechanisms. For different frequency regimes, different saturation mechanisms are identified.}, url = {http://link.aip.org/link/?GTP/133/101502/1}, publisher = {ASME}, ISSN = {0742-4795 (online), 1528-8919 (print)}, DOI = {10.1115/1.4002946}, author = {Schimek, S. and Moeck, J. P. and Paschereit, C. O.} } @Article { Goeke2011c, title = {An Innovative Combustion Technology for High-Efficiency Gas Turbines}, journal = {VGB PowerTech}, year = {2011}, volume = {10}, pages = {44--49}, ISSN = {1435-3199 (print)}, author = {G{\"o}ke, S. and Paschereit, C. O.} } @Article { Petz2011, title = {Global modes in a swirling jet undergoing vortex breakdown}, journal = {Physics of Fluids}, year = {2011}, volume = {23}, number = {9}, pages = {091102}, keywords = {bifurcation; confined flow; flow visualisation; fluid oscillations; jets; nozzles; shear turbulence; vortices;}, publisher = {AIP}, ISSN = {1070-6631 (print), 1089-7666 (online)}, DOI = {10.1063/1.3640007}, author = {Petz, C. and Hege, H. C. and Oberleithner, K. and Sieber, M. and Nayeri, C. N. and Paschereit, C. O. and Wygnanski, I. and Noack, B. R.} } @Article { Oberleithner2011c, title = {Salt overload damages the glycocalyx sodium barrier of vascular endothelium}, journal = {Pfl{\"u}gers Archiv European Journal of Physiology}, year = {2011}, volume = {462}, number = {4}, pages = {519-528}, abstract = {Sodium overload stiffens vascular endothelial cells in vitro and promotes arterial hypertension in vivo. The hypothesis was tested that the endothelial glycocalyx (eGC), a mesh of anionic biopolymers covering the surface of the endothelium, participates in the stiffening process. By using a mechanical nanosensor, mounted on an atomic force microscope, height (400 nm) and stiffness (0.25 pN/nm) of the eGC on the luminal endothelial surface of split-open human umbilical arteries were quantified. In presence of aldosterone, the increase of extracellular sodium concentration from 135 to 150 mM over 5 days (sodium overload) led the eGC shrink by 50\% and stiffening by 130\%. Quantitative eGC analyses reveal that sodium overload caused a reduction of heparan sulphate residues by 68\% which lead to destabilization and collapse of the eGC. Sodium overload transformed the endothelial cells from a sodium release into a sodium-absorbing state. Spironolactone, a specific aldosterone antagonist, prevented these changes. We conclude that the endothelial glycocalyx serves as an effective buffer barrier for sodium. Damaged eGC facilitates sodium entry into the endothelial cells. This could explain endothelial dysfunction and arterial hypertension observed in sodium abuse.}, affiliation = {Institute of Physiology II, University of M{\"u}nster, Robert-Koch-Str. 27b, 48149 M{\"u}nster, Germany}, keywords = {Biomedizin \& Life Sciences}, publisher = {Springer Berlin / Heidelberg}, ISSN = {0031-6768}, DOI = {10.1007/s00424-011-0999-1}, author = {Oberleithner, H. and Peters, W. and Kusche-Vihrog, K. and Korte, S. and Schillers, H. and Kliche, K. and Oberleithner, K.} } @Article { Oberleithner2011a, title = {Three-dimensional coherent structures in a swirling jet undergoing vortex breakdown: stability analysis and empirical mode construction.}, journal = {Journal of Fluid Mechanics}, year = {2011}, volume = {679}, pages = {383-414}, abstract = {The spatio-temporal evolution of a turbulent swirling jet undergoing vortex breakdown has been investigated. Experiments suggest the existence of a self-excited global mode having a single dominant frequency. This oscillatory mode is shown to be absolutely unstable and leads to a rotating counter-winding helical structure that is located at the periphery of the recirculation zone. The resulting time-periodic 3D velocity field is predicted theoretically as being the most unstable mode determined by parabolized stability analysis employing the mean flow data from experiments. The 3D oscillatory flow is constructed from uncorrelated 2D snapshots of particle image velocimetry data, using proper orthogonal decomposition, a phase-averaging technique and an azimuthal symmetry associated with helical structures. Stability-derived modes and empirically derived modes correspond remarkably well, yielding prototypical coherent structures that dominate the investigated flow region. The proposed method of constructing 3D time-periodic velocity fields from uncorrelated 2D data is applicable to a large class of turbulent shear flows.}, note = {Available on CJO}, url = {http://journals.cambridge.org/article_S0022112011001418}, DOI = {10.1017/jfm.2011.141}, author = {Oberleithner, K. and Sieber, M. and Nayeri, C. N. and Paschereit, C. O. and Petz, C. and Hege, H. C. and Noack, B. R. and Wygnanski, I.} } @Conference { Rukes2011, title = {Local linear stability analysis of a turbulent, swirling jet undergoing vortex breakdown}, year = {2011}, booktitle = {EUROMECH Colloquium 525 - Instabilities and transition in three-dimensional flows with rotation, 21--23 June 2011, {\'E}cole centrale de Lyon, France}, author = {Rukes, L. and Oberleithner, K. and Paschereit, C. O.} } @Conference { Oberleithner2011d, title = {On global modes in turbulent swirling jet experiments}, year = {2011}, booktitle = {9th ERCOFTAC SIG 33 Workshop, Progress in Transition Modeling and Control}, author = {Oberleithner, K. and Paschereit, C. O.} } @Inproceedings { Schimek2011b, title = {Identification of the flame describing function of a premixed swirl flame from LES}, year = {2011}, month = {9}, url = {http://www.combustion-institute.it/proceedings/MCS-7/papers/PEC/PEC-05.pdf}, booktitle = {Proceedings of 7th Mediterranean Combustion Symposium (MCS), Chia Laguna, Cagliari, Sardinia, Italy, September}, ISBN = {978-88-88104-12-6 (CD-ROM)}, author = {Krediet, H. J. and Beck, C. H. and Krebs, W. and Schimek, S. and Paschereit, C. O.} } @Inproceedings { Strangfeld2011b, title = {3D Visualisation of Measured Coherent Structures in a Swirling Water Flow}, year = {2011}, pages = {36.1--36.9}, booktitle = {Proceedings der 19. GALA-Fachtagung ''Lasermethoden in der Str{\"o}mungsmesstechnik'', 2011, Ilmenau, Germany}, ISBN = {978-3-9805613-7-2 (print)}, author = {Strangfeld, C. and G{\"o}ckeler, K. and Terhaar, S. and Paschereit, C. O.} } @Inproceedings { Goeke2011, title = {Combustion Of Natural Gas, Hydrogen And Bio-fuels At Ultra-wet Conditions}, year = {2011}, number = {ASME paper GT2011-45696}, booktitle = {Proc. ASME Turbo Expo 2011: Advancing Clean and Efficient Turbine Technology (GT2011), June 6-10, Vancouver, BC, Canada}, author = {G{\"o}ke, S. and Terhaar, S. and Schimek, S. and G{\"o}ckeler, K. and Paschereit, C. O.} } @Inproceedings { Eisele2011, title = {Experimental Investigation of Dynamic Load Control Strategies using Active Microflaps on Wind Turbine Blades}, year = {2011}, abstract = {Conventional wind turbine rotor blades are exposed to unsteady aerodynamic loads caused by wind gusts. Typically, the wind gusts have a duration of 1s to 10min, whereby maximum wind gusts with speeds 1.7 times faster than the hourly mean wind speed can occur [1]. These dynamic loads lead to undesired responses of the blade flap and chord-wise oscillations. The lifetime of a blade is significantly reduced by fatigue due to this effect. Furthermore, the tower is adversely affected by the resulting rotor dynamics. A proper way to minimize unsteady aerodynamic loads on rotor blades is to apply active flow control elements. Such solutions however require appropriate sensors and control strategies in order to ensure a stable operation. Designing a conventional controller for active flow control elements on a real wind turbine blade requires a very large amount of physical insights. However, the aerodynamics and aeroelastic effects on wind turbine blades are not yet well understood. Because of this lack, a feasible way of designing a controller is to use the so-called black box method. Thereby the controller is designed by observing inputs and outputs without taking into account the dynamics in between.}, url = {http://www.ewec2010proceedings.info/ewea2011/papers/170.pdf}, booktitle = {EWEA 2011 (European Wind Energy Association), Brussels, Belgium, 14-17 March}, author = {Eisele, O. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Schimek2011c, title = {Experimental investigation of the influence of high amplitude forcing and swirl fluctuations on the flow field and the transfer function of a swirl-stabilized flame}, year = {2011}, number = {AIAA paper no. 2011-5702}, booktitle = {47th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, San Diego, California, Jul 31 -- Aug 3}, author = {Schimek, S. and Moeck, J. P. and Paschereit, C. O.} } @Inproceedings { Kruger2011c, title = {Identification of Coherent Structures in a Turbulent Generic Swirl Burner using Large Eddy Simulations}, year = {2011}, number = {AIAA paper 2011-3549}, pages = {1--14}, abstract = {The isothermal flow dynamics of a generic swirl burner are studied employing large eddy simulation (LES). A sensitivity analysis was conducted, considering different mesh sizes and subgrid-scale models and the results were compared to experimental data. It was found that the overall influence of the computational grid and the subgrid-scale model was neglectable and the simulations were in line with the experiments. A dominant frequency was found in the turbulent kinetic energy spectrum representing a coherent structure. Moreover, by applying the proper orthogonal decomposition (POD) this structure could be identified as a convective helical instability. This helical instability and can be represented by a pair of modes, and is assumed to be triggered by a precessing vortex core (PVC).}, booktitle = {20th AIAA Computational Fluid Dynamics Conference, June 27-30, 2011, Honolulu, Hawaii, USA}, author = {Kr{\"u}ger, O. and Duwig, C. and G{\"o}ckeler, K. and Terhaar, S. and Strangfeld, C. and Paschereit, C. O. and Fuchs, L.} } @Inproceedings { Goeke2011b, title = {Investigation of NOx and CO Formation in a Premixed Swirl-Stabilized Flame at Ultra Wet Conditions}, year = {2011}, number = {AIAA paper no. 2011-5535}, booktitle = {47th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, San Diego, California, Jul 31 -- Aug 3}, author = {G{\"o}ke, S. and Schimek, S. and Fateev, A. and Clausen, S. and Kuhn, P. and Terhaar, S. and Paschereit, C. O.} } @Inproceedings { Kruger2011b, title = {Large Eddy Simulation of Ultra-Wet Premixed Flames for Gas Turbine Applications}, year = {2011}, pages = {1--6}, abstract = {The present study employs large eddy simulations (LES) to investigate a generic swirl-stabilized burner operated with methane at ultra-wet conditions. In order to investigate the reactive flow, a customized solver for handling low Mach number flows based on an implicit LES approach was developed. A reduced 4 steps / 7 species global scheme was used as combustion model . To compare the simulations with experiments, OH chemiluminescence pictures served as a reference.}, web_url = {Kruger2011b.pdf}, booktitle = {Proceedings of the European Combustion Meeting 2011, Jun 29 - Jul 1, Cardiff, UK}, author = {Kr{\"u}ger, O. and Duwig, C. and G{\"o}ke, S. and Paschereit, C. O. and Fuchs, L.} } @Inproceedings { vey2011, title = {Low Aspect Ratio Wing Flow Control at MAV Reynolds Numbers}, year = {2011}, volume = {2}, pages = {614-625}, url = {http://toc.proceedings.com/10945webtoc.pdf}, booktitle = {Proc. 51st Israel Annual Conference on Aerospace Sciences 2011, Feb 23-24, Tel-Aviv and Haifa, Israel}, ISBN = {978-1-61782-401-2}, author = {Vey, S. and Nayeri, C. N. and Greenblatt, D. and Paschereit, C. O.} } @Inproceedings { Sieber2011, title = {Model Design And Calibration For Closed-Loop Control Of Swirling Jet Instabilities}, year = {2011}, url = {http://www.it.cas.cz/files/DT2011/Sieber_A.pdf}, address = {Prague}, booktitle = {Colloquium Fluid Dynamics, Institute of Thermomechanics AS CR, v.v.i., Prague, 19--21 Oct}, author = {Sieber, M. and Oberleithner, K. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Terhaar2011, title = {Non-Reacting and Reacting Flow in a Swirl-Stabilized Burner for Ultra-Wet Combustion}, year = {2011}, number = {AIAA paper no. 2011-3584}, pages = {1--14}, abstract = {The flow field of a swirl-stabilized burner for ultra-wet combustion is experimentally investigated by assessing the isothermal and the reacting flow. The ultra-wet combustion technique promises high cycle efficiency and low NOx emissions. Investigations of the non- reacting flow field are carried out in a water tunnel facility and the reacting flow is assessed in an atmospheric combustion test rig. Experiments were conducted at a theoretical swirl number of 0.7 and Reynolds numbers in the range of 22,000 to 32,000. Particle Image Velocimetry and OH-Chemiluminescence are employed to measure the flow velocities as well as the spatial distribution of heat release. The effect of steam addition up to levels of 30\% of the air mass flow is investigated for natural gas fuel and mixtures of natural gas and hydrogen. The results show a strong impact of steam addition on the flow field and the position of the reaction zone. In particular, three different flow patterns were found. Dry flames and hydrogen flames show a broad inner recirculation zone with very low local turbulent kinetic energy. At high rates of steam dilution, the flow fields show good agreement to the non-reacting flow field in water as well as in isothermal air. At intermediate to high steam dilution rates the flame shows a trumpet like shape. Several sudden changes of the flow field and flame shapes could be observed for various operating conditions.}, booktitle = {Proc. 41st AIAA Fluid Dynamics Conference and Exhibit, 27-30 June, Honolulu, Hawaii}, ISBN = {978-1-61839167-4 (DVD)}, author = {Terhaar, S. and G{\"o}ckeler, K. and Schimek, S. and G{\"o}ke, S. and Paschereit, C. O.} } @Inproceedings { Kruger2011a, title = {Numerical Investigations of a Swirl-stabilized Premixed Flame at Ultra-Wet Conditions}, year = {2011}, number = {ASME paper GT2011-45866}, abstract = {The present study focuses on the numerical investigation of a generic swirl-stabilized burner operated with methane at ultra-wet conditions. The burner is fed with a preheated homogeneous mixture formed by steam and air. As a set of operating conditions atmospheric pressure, inlet temperature of 673 K, equivalence ratio of 0: 85 and a steam content of 30\% is applied. Large eddy simulations have been performed to investigate the flow features. In a first step the non-reacting flow field was in-vestigated with water as working medium. Comparison with Par-ticle Image Velocimetry (PIV) and Laser-Doppler Velocimetry (LDV) measurements conducted in a water tunnel facility showed that an excellent agreement within the experimental uncertainty is obtained for the flow field. A dominant frequency in the tur-bulent energy spectrum was identified, which corresponds to the motion associated with a precessing vortex core (PVC). In order to investigate the reactive flow in a second step, a customized solver for handling low Mach number reacting flows based on an implicit LES approach was developed. As reaction mechanism a reduced 4 steps / 7 species global scheme was used. To compare the simulations qualitatively with a wet flame, OH chemiluminescence pictures serve as a reference. The simula-tions showed a more compact flame compared to the OH pic-tures. Nevertheless, the prolongation and position of the flame were found to be reasonable. The reduced mechanism captures the main effects, such as the reduction of the peak and mean temperatures. Furthermore, the presence of a PVC in the react- ing flow could be determined and was not suppressed by heat- release.}, booktitle = {Proc. ASME Turbo Expo 2011: Advancing Clean and Efficient Turbine Technology (GT2011), June 6-10, Vancouver, BC, Canada}, author = {Kr{\"u}ger, O. and Duwig, C. and G{\"o}ke, S. and G{\"o}ckeler, K. and Paschereit, C. O. and Fuchs, L.} } @Inproceedings { Oberleithner2011b, title = {On the control of global modes in swirling jet experiments}, year = {2011}, volume = {318}, number = {3}, pages = {032050}, abstract = {The aim of this work is to control the self-excited global mode that concomitants vortex breakdown in turbulent swirling jets. This mode is characterized by a co-rotating counter winding single helical instability wave that originates from the jet center. Experiments show that the amplitude of this global mode is effectively reduced by exciting a double-helical mode in the outer shear layer. This mode is shown to be convective unstable at growth rates that are well predicted by spatial linear stability analysis. The dampening of the global mode occurs through an energy transfer between the inner and the outer shear layer. In preparation of closed-loop experiments, a reduced order model of the flow dynamics is developed based on five leading POD modes. The model is calibrated to flow�transients recorded via time-resolved PIV. A state estimator is designed that predicts the flow state from two hotwire probes. The performance of the estimator is validated in open-loop experiments. First results support the design of the model and state estimator.}, url = {http://stacks.iop.org/1742-6596/318/i=3/a=032050}, booktitle = {Journal of Physics: Conference Series}, event_place = {Warsaw}, event_name = {13th European Turbulence Conference (ETC13)}, event_date = {12-15 September 2011}, ISSN = {1742-6588 (Print), 1742-6596 (Online)}, DOI = {10.1088/1742-6596/318/3/032050}, author = {Oberleithner, K. and Sieber, M. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Cosic2011, title = {Open-Loop control of combustion instabilities and the role of the flame response to two-frequency forcing}, year = {2011}, number = {ASME paper GT2011-46503}, booktitle = {Proc. ASME Turbo Expo 2011: Advancing Clean and Efficient Turbine Technology (GT2011), June 6-10, Vancouver, BC, Canada}, author = {\'{C}osi\'{c}, B. and Bobusch, B. and Moeck, J. P. and Paschereit, C. O.} } @Inproceedings { Strangfeld2011a, title = {Parametric Investigations of the Leading Edge Vortex on a Delta Wing}, year = {2011}, number = {AIAA-2011-3895}, pages = {1--12}, booktitle = {20th AIAA Computational Fluid Dynamics Conference, June 27-30, 2011, Honolulu, Hawaii, USA}, author = {Strangfeld, C. and Nayeri, C. N. and Taubert, L. and Paschereit, C. O.} } @Inproceedings { Pechlivanoglou2011b, title = {Performance optimization of Wind Turbine Rotors with Active Flow Control}, year = {2011}, number = {ASME paper GT2011-45493}, abstract = {A control system consisting of a force sensor, a controller and the microflap as an actuator was designed and tested in the wind tunnel. For this purpose a test wing with constant cross section, based on the dedicated wind turbine airfoil AH 93-W-174 was equipped with a trailing edge microflap with a flap-chord of 1.6\%c. Measurements were accomplished at the large wind tunnel of the Herman F{\"o}ttinger Institute (HFI) of the TU-Berlin. Wind gusts were simulated by varying the angle of attack of the airfoil model with a maximum angular velocity of 2.2\(^{\circ}\)/s. The microflap could be deflected simultaneously with a deflection speed of approximately 300\(^{\circ}\)/s.}, booktitle = {Proc. ASME Turbo Expo 2011: Advancing Clean and Efficient Turbine Technology (GT2011), June 6-10, Vancouver, BC, Canada}, author = {Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Goeckeler2011, title = {Residence Time Distribution in a Swirl-Stabilized Combustor at Cold Conditions}, year = {2011}, number = {AIAA-2011-3585}, pages = {13}, abstract = {Reactor network models are widely used in studies of combustion kinetics. The mean residence time in the reactors is a crucial input for these models, however few attempts have been conceived so far to determine it accurately. In this study, the temporal and spatial distribution of a fluorescent tracer, injected as a short pulse, was measured using Highspeed planar laser-induced fluorescence (HS-PLIF), and Particle Image Velocimetry (PIV) was utilized for measuring the flow field. In a pulse experiment the tracer response in the combustor exit stream almost readily yields the residence time density function, which directly gives the mean residence time in the combustor. For a volume element within the combustor, the respective tracer response yields the time delay from the injection until the elements exit, but not its residence time, due to dispersion of the tracer input. The density function describes the deviation from the ideal transport in a plug flow and a perfectly mixed flow by considering two characteristic times: (1) a convective time delay \(\tau\)c, representing the time until the first detection of the tracer, and (2) a dispersive time delay \(\tau\)d, which characterizes the degree of dispersion upstream,and mixing within the respective volume element. A plug flow is solely described by \(\tau\)c, whereas a perfectly mixed flow is characterized only by \(\tau\)d. Time density functions were obtained at the injection holes, the combustion chamber inlet and outlet, as well as in an axicentric cross-section of the combustion chamber. The shape of density functions in the combustion chamber varies between that of an approx- imate plug flow and perfectly mixed flow, but mostly is represented by a superposition of the two. The distribution of \(\tau\)c indicates the path of the tracer through the combus- tor. By means of the \(\tau\)d distribution, zones of similar mixing characteristics are identified. The external recirculation zone (ERZ) is among these; however, only part of the internal recirculation zone (IRZ), that is less effected by entrainment from the jet, exhibits these similar mixing characteristics. Based on the experimental findings, a semi-empirical re- actor network model was developed applying an extended tanks-in-series approach. The model agrees very well with the measured time density functions. The transfer functions of the recirculation zones are used to determine the actual mean residence time in these zones. The mean residence time in the IRZ yields 21\% of the total combustor residence time and 25\% in the ERZ.}, booktitle = {Proc. 41st AIAA Fluid Dynamics Conference and Exhibit, 27-30 June, Honolulu, Hawaii}, ISBN = {978-1-61839167-4 (DVD)}, author = {G{\"o}ckeler, K. and Terhaar, S. and Lacarelle, A. and Paschereit, C. O.} } @Inproceedings { schroedinger2011, title = {The impact of periodical flow forcing on the mixing quality and flow structure in a swirl burner: numerial and experimental studies}, year = {2011}, number = {AIAA paper no. 2011-5747}, booktitle = {47th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, San Diego, California, Jul 31 -- Aug 3}, author = {Schr{\"o}dinger, C. and Lacarelle, A. and Oevermann, M. and Paschereit, C. O.} } @Inproceedings { moeck2011, title = {Unstable azimuthal modes in an annular Rijke tube: Dynamics and Control}, year = {2011}, booktitle = {Proc. of the 18th International Congress on Sound and Vibration (ICSV), July 10-14, Rio de Janeiro, Brazil}, ISBN = {978-85-63243-01-0 (CDROM}, author = {Moeck, J. P. and Paschereit, C. O.} } @Article { konle2011, title = {Application of Fiber-Optical Microphone for Thermo-Acoustic Measurements}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2010}, month = {9}, day = {14}, volume = {133}, number = {1}, pages = {011602 (8 Pages)}, keywords = {acoustic measurement; acoustic wave interferometry; fibre optic sensors; microphones}, url = {http://link.aip.org/link/?GTP/133/011602/1}, publisher = {ASME}, ISSN = {0742-4795 (online), 1528-8919 (print)}, DOI = {10.1115/1.4001983}, author = {Konle, H. J. and Paschereit, C. O. and R{\"o}hle, I.} } @Article { Bothien2010, title = {Comparison of Linear Stability Analysis with Experiments by Actively Tuning the Acoustic Boundary Conditions of a Premixed Combustor}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2010}, month = {8}, day = {20}, volume = {32}, number = {12}, pages = {121502 (10 pages)}, abstract = {Linear stability analysis by means of low-order network models is widely spread in industry and academia to predict the thermoacoustic characteristics of combustion systems. Even though a vast amount of publications on this topic exist, much less is reported on the predictive capabilities of such stability analyses with respect to real system behavior. In this sense, little effort has been made on investigating if predicted critical parameter values, for which the combustion system switches from stability to instability, agree with experimental observations. Here, this lack of a comprehensive experimental validation is addressed by using a model-based control scheme. This scheme is able to actively manipulate the acoustic field of a combustion test rig by imposing quasi-arbitrary reflection coefficients. It is employed to continuously vary the downstream reflection coefficient of an atmospheric swirl-stabilized combustion test rig from fully reflecting to anechoic. By doing so, the transient behavior of the system can be studied. In addition to that, an extension of the common procedure, where the stability of an operating point is classified solely based on the presence of high amplitude pressure pulsations and their frequency, is given. Generally, the predicted growth rates are only compared with measurements with respect to their sign, which obviously lacks a quantitative component. In contrast to that, in this paper, validation of linear stability analysis is conducted by comparing calculated and experimentally determined linear growth rates of unstable modes. Besides this, experimental results and model predictions are also compared in terms of frequency of the least stable mode. Excellent agreement between computations from the model and experiments is found. The concept is also used for active control of combustion instabilities. By tuning the downstream reflectivity of the combustion test rig, thermoacoustic instabilities can be suppressed. The underlying mechanism is an increase in the acoustic energy losses across the system boundary.}, url = {http://link.aip.org/link/?GTP/132/121502/1}, publisher = {ASME}, ISSN = {0742-4795 (online), 1528-8919 (print)}, DOI = {10.1115/1.4000806}, author = {Bothien, M. R. and Moeck, J. P. and Paschereit, C. O.} } @Article { SchuermansGPGP2010, title = {Thermoacoustic Modeling of a Gas Turbine Using Transfer Functions Measured Under Full Engine Pressure}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2010}, month = {8}, day = {10}, volume = {132}, number = {11}, pages = {111503 (9 pages)}, abstract = {Thermoacoustic transfer functions of a full-scale gas turbine burner operating under full engine pressure have been measured. The excitation of the high-pressure test facility was done using a siren that modulated a part of the combustion airflow. Pulsation probes have been used to record the acoustic response of the system to this excitation. In addition, the flame's luminescence response was measured by multiple photomultiplier probes and a light spectrometer. Three techniques to obtain the thermoacoustic transfer function are proposed and employed: two acoustic-optical techniques and a purely acoustic technique. The first acoustical-optical technique uses one single optical signal capturing the chemiluminescence intensity of the flame as a measure for the heat release in the flame. This technique only works if heat release fluctuations in the flame have only one generic source, e.g., equivalence ratio or mass flow fluctuations. The second acoustic-optical technique makes use of the different response of the flame's luminescence at different optical wavelengths bands to acoustic excitation. It also works, if the heat release fluctuations have two contributions, e.g., equivalence ratio and mass flow fluctuation. For the purely acoustic technique, a new method was developed in order to obtain the flame transfer function, burner transfer function, and flame source term from only three pressure transducer signals. The purely acoustic method could be validated by the results obtained from the acoustic-optical techniques. The acoustic and acoustic-optical methods have been compared and a discussion on the benefits and limitations of each is given. The measured transfer functions have been implemented into a nonlinear, three-dimensional, time domain network model of a gas turbine with an annular combustion chamber. The predicted pulsation behavior shows a good agreement with pulsation measurements on a field gas turbine.}, url = {http://link.aip.org/link/?GTP/132/111503/1}, publisher = {ASME}, ISSN = {0742-4795 (online), 1528-8919 (print)}, DOI = {10.1115/1.4000854}, author = {Schuermans, B. and Guethe, F. and Pennell, D. and Guyot, D. and Paschereit, C. O.} } @Article { Bothien2010a, title = {Tuning of the acoustic boundary conditions of combustion test rigs with active control: Extension to actuators with nonlinear response}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2010}, month = {6}, day = {17}, volume = {132}, number = {9}, pages = {091503 (10 pages)}, abstract = {In the design process, new burners are generally tested in combustion test rigs. With these experiments, as well as with computational fluid dynamics, finite element calculations, and low-order network models, the burner's performance in the full-scale engine is sought to be predicted. Especially, information about the thermoacoustic behavior and the emissions is very important. As the thermoacoustics strongly depend on the acoustic boundary conditions of the system, it is obvious that test rig conditions should match or be close to those of the full-scale engine. This is, however, generally not the case. Hence, if the combustion process in the test rig is stable at certain operating conditions, it may show unfavorable dynamics at the same conditions in the engine. In previous works, the authors introduced an active control scheme, which is able to mimic almost arbitrary acoustic boundary conditions. Thus, the test rig properties can be tuned to correspond to those of the full-scale engine. The acoustic boundary conditions were manipulated using woofers. In the present study, an actuator with higher control authority is investigated, which could be used to apply the control scheme in industrial test rigs. The actuator modulates an air mass flow to generate an acoustic excitation. However, in contrast to the woofers, it exhibits a strong nonlinear response regarding amplitude and frequency. Thus, the control scheme is further developed to account for these nonlinear transfer characteristics. This modified control scheme is then applied to change the acoustic boundary conditions of an atmospheric swirl-stabilized combustion test rig. Excellent results were obtained in terms of changing the reflection coefficient to different levels. By manipulating its phase, different resonance frequencies could be imposed without any hardware changes. The nonlinear control approach is not restricted to the actuator used in this study and might therefore be of use for other actuators as well.}, url = {http://link.aip.org/link/?GTP/132/091503/1}, publisher = {ASME}, ISSN = {0742-4795 (online), 1528-8919 (print)}, DOI = {10.1115/1.4000599}, author = {Bothien, M. R. and Paschereit, C. O.} } @Article { Albrecht2010, title = {Instability control by premixed pilot flames}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2010}, month = {1}, day = {12}, volume = {132}, number = {4}, pages = {041501 (8 pages)}, abstract = {Premixed flames of swirl-stabilized combustors (displaced half-cone) are susceptible to thermo-acoustic instabilities, which should be avoided under all operating conditions in order to guarantee a long service life for both stationary and aircraft gas turbines. The source of this unstable flame behavior can be found in a transition of the premix flame structure between two stationary conditions that can be easily excited by fuel fluctuations, coherent structures within the flow, and other mechanisms. Pilot flames can alleviate this issue either by improving the dynamic stability directly or by sustaining the main combustion process at operating points where instabilities are unlikely. In the present study, the impact of two different premixed pilot injections on the combustion stability is investigated. One of the pilot injector (pilot flame injector) was located upstream of the recirculation zone at the apex of the burner. The second one was a pilot ring placed at the burner outlet on the dump plane. A noticeable feature of the pilot injector was that an ignition device allowed for creating pilot premixed flames. The present investigation showed that these premixed pilot flames were able to suppress instabilities over a wider fuel/air ratio range than the conventional premixed pilot injection alone. Furthermore, it was possible to prevent instabilities and maintain the flame burning near the lean blowout when a percentage of the fuel was premixed with air and injected through the pilot ring. NOx emissions were significantly reduced.}, url = {Ehttp://link.aip.org/link/?GTP/132/041501/1}, publisher = {ASME}, ISSN = {0742-4795 (online), 1528-8919 (print)}, DOI = {10.1115/1.3019293}, author = {Albrecht, P. and Bade, S. and Lacarelle, A. and Paschereit, C. O. and Gutmark, E. J.} } @Article { Konle2010, title = {A fiber optical microphone based on a Fabry-Perot interferometer applied for thermo-acoustic measurements.}, journal = {Measurement Science and Technology}, year = {2010}, volume = {21}, number = {1}, pages = {015302}, abstract = {A high-temperature resistant fiber-optical microphone (FOM) was developed and successfully applied in a combustion chamber (~1.2 \(\times\) 105 Pa, ~1400 K gas temperature) with thermo-acoustic oscillations resulting in a sound pressure level of 154 dB at the dominant frequency. The core of the optical set-up used for the FOM is a Fabry-Perot interferometer. To create an acoustical sensor based on this type of interferometer, a new method of generation and postprocessing of the interference signal was developed. The simple replaceability of the used membrane material allows the adaptation of the sensor sensitivity to the projected field of application.}, url = {http://iopscience.iop.org/0957-0233/21/1/015302/pdf/0957-0233_21_1_015302.pdf}, ISSN = {0957-0233 (Print), 1361-6501 (Online)}, DOI = {10.1088/0957-0233/21/1/015302}, author = {Konle, H. J. and R{\"o}hle, I. and Paschereit, C. O.} } @Article { Lacarelle2010, title = {Combination of image postprocessing tools to identify coherent structures of premixed flames}, journal = {AIAA Journal}, year = {2010}, volume = {48}, number = {8}, pages = {1708-1720}, ISSN = {00011452}, DOI = {10.2514/1.J050188}, author = {Lacarelle, A. and Luchtenburg, D. M. and Bothien, M. R. and Noack, B. R. and Paschereit, C. O.} } @Article { Paschereit2010, title = {Neues Verfahren bei der Verbrennung von Gasen}, journal = {''Energien f{\"u}r die Zukunft'', Zeitschrift f{\"u}r Internationale Absolventen der Technischen Universit{\"a}t Berlin}, year = {2010}, volume = {65}, pages = {6-7}, url = {http://www.alumni.tu-berlin.de/fileadmin/Redaktion/ABZ/PDF/TUI/65/paschereit_TUI65.pdf}, author = {Paschereit, C. O.} } @Article { Paschereit2010a, title = {Verbrennung von Gasen}, journal = {\(\eta\)[energie] Energieeffizienz \& kohlenstoffarme Energietechnik}, year = {2010}, number = {2}, pages = {8-11}, abstract = {Mit einem v{\"o}llig neuen Ansatz entwickelt der Lehrstuhl f{\"u}r Str{\"o}mungsmechanik an der TU Berlin ein Verfahren, das die Verbrennung in Gasturbinen den Anforderungen einer modernen Energiepolitik anpasst: Bei geringerem Ressourcenverbrauch soll eine h{\"o}here Effizienz erreicht werden. Gleichzeitig werden Gasturbinen f{\"u}r die Verbrennung alternativer Rohstoffe fit gemacht. Prof. Dr. Christian Oliver Paschereit und Sebastian G{\"o}ke berichten {\"u}ber dieses Vorhaben, das von der EU mit gro{\ss}z{\"u}gigen F{\"o}rdermitteln ausgezeichnet wurde.}, url = {http://www.etaenergie.com/news/9,237376/\%CE\%B7\%5Benergie\%5D-2-2010/Verbrennung-von-Gasen.html}, publisher = {succidia AG}, author = {Paschereit, C. O. and G{\"o}ke, S.} } @Conference { Oberleithner2010c, title = {Self excited oscillations in swirling jets: Stability analysis and empirical mode construction}, year = {2010}, series = {63rd Annual DFD Meeting}, organization = {American Physical Society}, author = {Oberleithner, K. and Nayeri, C. N. and Paschereit, C. O. and Wygnanski, I.} } @Conference { Oberleithner2010d, title = {Self-excited global modes in swirling jets undergoing vortex breakdown}, year = {2010}, event_place = {Altes Koenigliches Kurhaus, Bad Reichenhall, Germany}, event_name = {8th Euromech Fluid Mechanics Conference}, author = {Oberleithner, K. and Nayeri, C. N. and Paschereit, C. O. and Wygnanski, I.} } @Inproceedings { Moeck2010, title = {A Zero-Mach Solver and Reduced Order Acoustic Representations for Modeling and Control of Combustion Instabilities}, year = {2010}, month = {4}, volume = {108}, pages = {291--306}, abstract = {Thermoacoustic instabilities are a serious problem for lean premixed combustion systems. Due to different time and length scales associated with the flow field, combustion, and acoustics, numerical computations of thermoacoustic phenomena are conceptually challenging. Using these methods to successfully design active control strategies is therefore difficult. This work presents a coupled method for the simulation of thermoacoustic instabilities in low Mach number reacting flows. The acoustics are represented by an experimentally identified reduced order model. A zero-Mach solver is used for the flame dynamics on the hydrodynamic scale. Two control schemes are employed to suppress thermoacoustic oscillations, equivalence ratio modulation and control of the acoustic boundary conditions. Both methods are shown to be capable of effectively diminishing the instability.}, editor = {King, R.}, publisher = {Springer-Verlag Berlin}, series = {Notes on Numerical Fluid Mechanics and Multidisciplinary Design}, booktitle = {Active Flow Control II, Papers Contributed to the Conference ''Active Flow Control II 2010'', Berlin, Germany, May 26 to 28, 2010}, ISBN = {978-3-642-11734-3 (print), 978-3-642-11735-0 (online)}, DOI = {10.1007/978-3-642-11735-0_19}, author = {Moeck, J. P. and Scharfenberg, C. and Paschereit, C. O. and Klein, R.} } @Inproceedings { Lacarelle2010a, title = {Modeling the fuel/air mixing to control the pressure pulsations and NOx emissions in a lean premixed combustor}, year = {2010}, month = {4}, volume = {108}, pages = {307--321}, abstract = {This paper presents an overviewof the methodology developed to predict, control and optimize the NOx emissions and stability of lean premixed combustors. Investigations are performed firstly in cold flow and are validated with reacting flow measurements. A new cold flow mixing model describes the relevant characteristics of the fuel/airmixing, i.e. themixing quality and convective time delays, for different operating points of the system.Measurements in the combustor are performed to correct the flame position effect or calibrate the cold flowresults.The model is for the first time implemented in an extremum seeking controller to optimize the emissions and pressure pulsations of the combustor by adjusting the fuel mixing profile. A further increase of the fuel/air mixing, necessary for further NOx reductions, with pulsating fuel injection, is demonstrated. At the end, the developed adaptive control strategies demonstrate opportunities for future efficiency increases in industrial combustors.}, editor = {King, Rudibert}, publisher = {Springer-Verlag Berlin}, series = {Notes on Numerical Fluid Mechanics and Multidisciplinary Design}, booktitle = {Active Flow Control II, Papers Contributed to the Conference ''Active Flow Control II 2010'', Berlin, Germany, May 26 to 28, 2010}, ISBN = {978-3-642-11734-3 (print), 978-3-642-11735-0 (online)}, DOI = {10.1007/978-3-642-11735-0_20}, author = {Lacarelle, A. and Moeck, J. P. and Paschereit, C. O. and Gelbert, G. and King, R. and Luchtenburg, D. M. and Noack, B. R. and Kasten, J. and Hege, H. C.} } @Inproceedings { Lacarelle2010c, title = {A Quantitative Link Between Cold-flow Scalar Unmixedness And NOx Emissions In A Conical Premixed Burner}, year = {2010}, number = {ASME paper GT2010-23132}, pages = {919-931}, abstract = {The feasibility of using cold flow measurements in a conical swirl-inducing burner to predict the fuel/air mixture probability density function (PDF) at the flame location in a staged premixed swirl-inducing burner is discussed in the present work. Particle Image Velocity (PIV) measurements are used to investigate the impact of the flame on the mean and coherent velocity field upstream of the premixed flame of a conical swirl-inducing burner. When the flame does not anchor inside the burner, a good agreement between the reacting and the cold-flow fields is ensured. The scalar mixing field, dominated by coherent concentration fluctuations, is thus marginally affected by the flame. In this case, a correction of the mixture PDF, recorded in a water test rig at the burner outlet with planar laser-induced fluorescence (PLIF), can be used to estimate the mixture PDF at the flame location. This correction is based on the exponential decay of the mixture variance associated with the flame-position information of the reacting flow. An experimental curve fitting and a chemical-reactor network model confirm that the resulting PDF approximates the real unmixedness at the flame better than the measured mixture PDF at the burner outlet. When the flame is anchored inside the burner, the correction approach does not apply anymore, due to the strong flow field changes. The methodology presented allows to quantitatively predict the mixture PDF at the flame location for different total powers, preheating temperatures, and equivalence ratios. The simple mixing model and reactor network model are able to satisfyingly capture the NOx emissions when the flame stabilizes completely downstream of the burner.}, url = {http://link.aip.org/link/abstract/ASMECP/v2010/i43970/p919/s1}, publisher = {ASME}, booktitle = {Proc. ASME Turbo Expo 2010: Power for Land, Sea, and Air (GT2010), June 14-18, Glasgow, Scotland}, ISBN = {978-0-7918-4397-0}, DOI = {10.1115/GT2010-23132}, author = {Lacarelle, A. and G{\"o}ke, S. and Paschereit, C. O.} } @Inproceedings { Pechlivanoglou2010, title = {Active aerodynamic control of wind turbine blades with high deflection flexible flaps}, year = {2010}, number = {AIAA paper no. 2010-644}, url = {http://pdf.aiaa.org/preview/2010/CDReadyMASM10_1812/PV2010_644.pdf}, booktitle = {48th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition, January 4 - 7, 2010, Orlando, Florida, USA}, author = {Pechlivanoglou, G. and Wagner, J. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Singh2010, title = {Active Control of an Incompressible Axisymmetric Jet using Flaps and Zero Mass-Flux Excitation}, year = {2010}, number = {AIAA paper no. 2010-4417}, url = {http://pdf.aiaa.org/preview/2010/CDReadyMFD10_2119/PV2010_4417.pdf}, booktitle = {5th Flow Control Conference, 28 June - 1 July, 2010, Chicago, Illinois, USA}, author = {Singh, Y. and Mueller-Vahl, H. and Greenblatt, D. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Moeck2010a, title = {Aktive Kontrolle thermoakustischer Instabilit{\"a}ten in einem annularen Rijke Rohr}, year = {2010}, booktitle = {Proc. DAGA 2010, Berlin, Germany}, author = {Moeck, J. P. and Gelbert, G. and Paul, M. and Paschereit, C. O. and King, R.} } @Inproceedings { Schimek2010, title = {An Experimental Investigation of the Nonlinear Flame Response of an Atmospheric Swirl-Stabilized Premixed Flame}, year = {2010}, number = {ASME paper GT2010-22827}, pages = {665-675}, url = {http://link.aip.org/link/abstract/ASMECP/v2010/i43970/p665/s1}, publisher = {ASME}, booktitle = {Proc. ASME Turbo Expo 2010: Power for Land, Sea, and Air (GT2010), June 14-18, Glasgow, Scotland}, ISBN = {978-0-7918-4397-0}, DOI = {10.1115/GT2010-22827}, author = {Schimek, S. and Moeck, J. P. and Paschereit, C. O.} } @Inproceedings { Konle2010a, title = {Application of fiber-optical microphone for thermo-acoustic measurements}, year = {2010}, number = {ASME paper no. GT2010-22022}, pages = {1--10}, abstract = {A high temperature resistant fiber optical microphone (FOM) was developed and successfully applied in a combustion chamber at a thermal power of 8.4kW to measure thermo-acoustic oscillations at a frequency of 85Hz and a sound pressure level of 154dB. The sensor head temperature was estimated to ~ 1000K. The core of the optical setup used for the FOM is a Fabry-Perot interferometer. To create an acoustical sensor based on this type of interferometer, a new method of generation and postprocessing of the interference signal was developed. The simple replaceability of the sensor membrane reduces the requirements concerning the sensor handling compared to conventional condenser microphones and allows the adaption of the sensor sensitivity to its application case changing the membrane stiffness.}, url = {http://link.aip.org/link/abstract/ASMECP/v2010/i43987/p1/s1}, publisher = {ASME}, booktitle = {Proc. ASME Turbo Expo 2010: Power for Land, Sea, and Air (GT2010), June 14-18, Glasgow, Scotland}, ISBN = {978-0-7918-4398-7}, DOI = {10.1115/GT2010-22022}, author = {Konle, H. J. and R{\"o}hle, I. and Paschereit, C. O.} } @Inproceedings { Schroedinger2010, title = {CFD modeling of the influence of fuel staging on the mixing quality and flame characteristics in lean premixed combustor}, year = {2010}, number = {GT2010-22910}, pages = {777-789}, abstract = {In this paper, we investigate the feasibility and limitation of modeling non reacting and reacting flows of a premixed burner with steady RANS. The burner investigated here is a standard industrial swirl-inducing burner equipped with a staging of fuel injection. The simulation results on mixing quality, flame shape and position and convective time delays are compared to measurements which are performed in a water test rig and in a combustion chamber. The RANS simulations can qualitatively capture the trends observed from experimental data. The simulated mixing quality evolves in a similar way as the experimental data when the fuel distribution is changed. Using a turbulent Schmidt number of 0.2, the absolute values are in good agreement with the measured ones. Variations of the fuel injection distribution lead to changes in the flame shape and its stabilization location. The simulated reacting flow optimized with respect to the turbulent Schmidt/Prandtl number (Sct /Prt = 0.55) is able to predict the changes in flame shape and flame position. However, the shifting of the flame is not as distinct as observed in the experiments. This explains that variations in simulated convective time delays are also smaller than in reality. Nevertheless, the qualitative characteristics of the time delays depending on the fuel distribution parameter can be reproduced and absolute values are generally similar to those of the measurements.}, url = {http://link.aip.org/link/abstract/ASMECP/v2010/i43970/p777/s1}, publisher = {ASME}, booktitle = {Proc. ASME Turbo Expo 2010: Power for Land, Sea, and Air (GT2010), June 14-18, Glasgow, Scotland}, ISBN = {978-0-7918-4397-0}, DOI = {10.1115/GT2010-22910}, author = {Schr{\"o}dinger, C. and Kr{\"u}ger, O. and Lacarelle, A. and Oevermann, M. and Paschereit, C. O.} } @Inproceedings { guyot2010b, title = {CH*/OH* Chemiluminescence Response of an Atmospheric Premixed Flame Under Varying Operating Conditions}, year = {2010}, volume = {2010}, number = {GT2010-23135}, pages = {933-944}, abstract = {In this work the relationship between the ratio of the global CH* and OH* flame chemiluminescece and the global equivalence ratio of a technically premixed swirl-stabilized flame is investigated. The burner allows for a modification of the premix fuel injection pattern. The global flame chemiluminescence is monitored by a high-sensitivity light spectrometer and multiple photo-multipliers. The photo-multipliers were equipped with narrow optical band-pass filters and recorded the flame's OH*, CH* and CO2* chemiluminescence intensity. To ensure an approximately uniform equivalence ratio distribution in the combustion zone, the spatial OH* and CH* flame chemiluminescence was recorded simultaneously with one ICCD camera using a special optical setup, which incorporated among other things one fully reflective and one semi-reflective mirror and appropriate optical filters. The flame chemiluminescence intensity was mapped for a range of equivalence ratios and air mass flows. The mapping shows that (as stated for perfectly premixed flames in the literature) the OH*, CH* and CO2* intensity of the investigated flame depends linearly on the air mass flow and exponentially on the equivalence ratio. Hence for the investigated operating conditions (i.e., quasi premix conditions) the global CH*/OH* intensity can be employed as a measure of the global equivalence ratio for the operating conditions investigated in this work. However, the contribution of broadband CO2* chemiluminescence in the wave length range of CH* chemiluminescence has to be accounted for.}, url = {http://link.aip.org/link/abstract/ASMECP/v2010/i43970/p933/s1}, publisher = {ASME}, booktitle = {Proc. ASME Turbo Expo 2010: Power for Land, Sea, and Air (GT2010), June 14-18, Glasgow, Scotland}, ISBN = {978-0-7918-4397-0}, DOI = {10.1115/GT2010-23135}, author = {Guyot, D. and Guethe, F. and Schuermans, B. and Lacarelle, A. and Paschereit, C. O.} } @Inproceedings { Goeke2010, title = {Computational and experimental study of premixed combustion at ultra wet conditions}, year = {2010}, number = {ASME paper no. GT2010-23417}, pages = {1125--1135}, abstract = {Humidified gas turbines (HGT), operating with humidified air, promise a higher efficiency compared to dry gas turbines, as well as reduced NOx emissions. In this study, premixed, near-stoichiometric combustion was investigated for gas turbine applications at ultra wet conditions with steam levels up to 35w\%. Based on a generic burner, an experimental study was conducted for the combustion of natural gas at atmospheric pressure. The influence of humidity on emissions and flammability limits was investigated for different inlet temperatures, swirl numbers, and fuel injection strategies. At near-stoichiometric conditions, a degree of humidity of 35w\% was achieved with a stable flame and single-digit NOx and CO emissions. In experiments conducted in a water tunnel, the flow field of the combustor was investigated using Laser Doppler Anemometry and Laser-induced Fluorescence. In addition to the experiments, a kinetic assessment of the emission formation was conducted with a reactor network, using a combination of several perfectly stirred reactors. The results of these simulations confirm the experimental findings.}, url = {http://link.aip.org/link/abstract/ASMECP/v2010/i43970/p1125/s1}, booktitle = {Proc. ASME Turbo Expo 2010: Power for Land, Sea, and Air (GT2010), June 14-18, Glasgow, Scotland}, ISBN = {978-0-7918-4397-0}, DOI = {10.1115/GT2010-23417}, author = {G{\"o}ke, S. and G{\"o}ckeler, K. and Kr{\"u}ger, O. and Paschereit, C. O.} } @Inproceedings { Goeckeler2010, title = {Enhanced Recirculation in the Cold Flow Field of a Swirl-stabilized Burner for Ultra Wet Combustion}, year = {2010}, booktitle = {Proceedings of 3rd International Conference on Jets, Wakes and Separated Flows (ICJWSF), Cincinnati, Ohio}, author = {G{\"o}ckeler, K. and G{\"o}ke, S. and Schimek, S. and Paschereit, C. O.} } @Inproceedings { Pfeifer2010, title = {Experimentelle Validierung der Rekonstruktion von Schallquellen in einem St{\"o}mungskanal}, year = {2010}, booktitle = {36. Deutsche Jahrestagung f{\"u}r Akustik, Dresden, 15.03. - 18.03.2010}, author = {Pfeifer, C. and Pardowitz, B. and Paschereit, C. O. and Enghardt, L.} } @Inproceedings { Pechlivanoglou2010a, title = {Fixed Leading Edge Auxiliary Wing as a Performance Increasing Device for HAWT Blades}, year = {2010}, url = {http://10.dewek.de/fileadmin/pdf/abstracts/S15_3.pdf}, booktitle = {Proceedings of DEWEK 2010, 17-18 November 2010, Bremen, Germany}, author = {Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Eisele2010, title = {Flow Control Using Plasma Actuators at the Root Region of Wind Turbine Blades}, year = {2010}, url = {http://smart-blade.com/fileadmin/downloads/abstract_plasma.pdf}, booktitle = {Proceedings of DEWEK 2010, 17-18 November 2010, Bremen, Germany}, author = {Eisele, O. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Oberleithner2010b, title = {Growth of disturbances in an axisymmetric swirling jet: Linear stability analysis and empirical validation}, year = {2010}, booktitle = {Proceedings of 3rd International Conference on Jets, Wakes and Separated Flows (ICJWSF), Cincinnati, Ohio}, author = {Oberleithner, K. and Kuhn, P. and Nayeri, C. N. and Paschereit, C. O. and Wygnanski, I.} } @Inproceedings { Marten2010a, title = {Integration of a WT Blade Design tool in XFOIL/XFLR5}, year = {2010}, url = {http://10.dewek.de/fileadmin/pdf/abstracts/S15_4.pdf}, booktitle = {Proceedings of DEWEK 2010, 17-18 November 2010, Bremen, Germany}, author = {Marten, D. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Konle2010b, title = {Laseroptische Messung des akustischen D{\"a}mpfungsverhaltens von Linern}, year = {2010}, booktitle = {36. Deutsche Jahrestagung f{\"u}r Akustik, Fortschritte der Akustik - DAGA 2010, 15.-18. M{\"a}rz 2010 Berlin, Germany}, author = {Konle, H. J. and R{\"o}hle, I. and Paschereit, C. O.} } @Inproceedings { Vey2010, title = {Leading edge and wing tip flow control on low aspect ratio wings}, year = {2010}, number = {AIAA paper no. 2010-4865}, url = {http://pdf.aiaa.org/preview/2010/CDReadyMFD10_2120/PV2010_4865.pdf}, booktitle = {40th Fluid Dynamics Conference and Exhibit, June 28 - July 1, 2010, Chicago, Illinois}, author = {Vey, S. and Greenblatt, D. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Moeck2010b, title = {Nonlinear Interactions of Multiple Linearly Unstable Thermoacoustic Modes}, year = {2010}, publisher = {Technische Universit{\"a}t M{\"u}nchen}, booktitle = {Proceedings of the Int'l Summer School and Workshop on Non-Normal and Nonlinear Effects in Aero- and Thermoacoustics}, author = {Moeck, J. P. and Paschereit, C. O.} } @Inproceedings { Vey2010a, title = {Plasma flow control on low aspect ratio wings at low Reynolds numbers}, year = {2010}, number = {AIAA paper no. 2010-1222}, url = {http://pdf.aiaa.org/preview/2010/CDReadyMASM10_1812/PV2010_1222.pdf}, booktitle = {48th AIAA Aerospace Science Meeting, January 4 - 7, 2010, Orlando, Florida, USA}, author = {Vey, S. and Nayeri, C. N. and Paschereit, C. O. and Greenblatt, D.} } @Inproceedings { Lacarelle2010b, title = {Scalar Mixing Enhancement In A Swirl Stabilized Combustor Trough Passive And Active Injection Control}, year = {2010}, number = {AIAA paper no. 2010-1332}, web_url2 = {http://pdf.aiaa.org/preview/2010/CDReadyMASM10_1812/PV2010_1332.pdf}, booktitle = {48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition, Jan. 4-7, 2010, Orlando, Florida, USA}, author = {Lacarelle, A. and Matho, L. and Paschereit, C. O.} } @Inproceedings { Kastantin2010, title = {Sharp Leading Edge Delta wing Control at Low Reynolds Number}, year = {2010}, number = {AIAA paper no. 2010-4864}, web_url2 = {http://pdf.aiaa.org/preview/2010/CDReadyMFD10_2120/PV2010_4864.pdf}, booktitle = {40th Fluid Dynamics Conference and Exhibit, 28 June - 1 July 2010, Chicago, Illinois}, author = {Kastantin, Y. and Vey, S. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Pechlivanoglou2010b, title = {The Effect Of Distributed Roughness On The Power Performance Of Wind Turbines}, year = {2010}, number = {ASME paper no. GT2010-23258}, pages = {845-855}, abstract = {The effects of distributed roughness on wind turbines are extensively investigated in this paper. The sources of roughness are identified and analyzed and their effects on airfoil are estimated from simulations and measured with wind tunnel measurements. In addition to the environmental and manufacturing induced roughness, several forms of roughness-related shape deviations are investigated and their effects on the aerodynamic performance of airfoils is qualitatively predicted through numerical simulations. The actual effects of roughness on wind turbine performance are also presented through power production measurements of wind turbines installed in sandy environments. These measurements are correlated with simulated power predictions, utilizing a steady state BEM code.}, url = {http://link.aip.org/link/abstract/ASMECP/v2010/i44007/p845/s1}, publisher = {ASME}, booktitle = {Proc. ASME Turbo Expo 2010: Power for Land, Sea, and Air (GT2010), June 14-18, Glasgow, Scotland}, ISBN = {978-0-7918-4400-7}, DOI = {10.1115/GT2010-23258}, author = {Pechlivanoglou, G. and F{\"u}hr, S. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Moeck2010c, title = {Thermoacoustic Instabilities in an Annular Rijke tube}, year = {2010}, number = {ASME paper no. GT2010-23577}, pages = {1219-1232}, abstract = {Thermoacoustic instabilities are a major concern in the design of gas turbine combustors. Most modern combustion chambers have an annular shape with multiple circumferentially arranged burners and, accordingly, suffer often from azimuthal instability modes. However, due to the complexity of a full annular system with a large number of burners, most experimental and numerical studies focus on single burner systems with essentially purely longitudinal acoustics. In the present work, we therefore introduce a thermoacoustic surrogate system -- an annular Rijke tube -- which, albeit its simplicity, possesses the basic mechanisms to feature unstable azimuthal modes. As in a conventional Rijke tube, the sources of mean and unsteady heat release in our set-up are electrically driven heating grids. Different azimuthal instability modes are observed in the experiment, and the effect of two types of circumferential variations of the power input is investigated. A full suppression of the unstable modes is achieved by the application of an elementary feedback controller. The experimental investigations are accompanied by corresponding calculations with a low-order system model. Theoretical and experimental results are found to agree well.}, url = {http://link.aip.org/link/abstract/ASMECP/v2010/i43970/p1219/s1}, publisher = {ASME}, booktitle = {Proc. ASME Turbo Expo 2010: Power for Land, Sea, and Air (GT2010), June 14-18, Glasgow, Scotland}, ISBN = {978-0-7918-4397-0}, DOI = {10.1115/GT2010-23577}, author = {Moeck, J. P. and Paul, M. and Paschereit, C. O.} } @Miscellaneous { Paschereit2010b, title = {Flow control and ist applications}, year = {2010}, booktitle = {Invited Talk, 3rd International Conference on Jets, Wakes and Separated Flows (ICJWSF), Cincinnati, Ohio}, author = {Paschereit, C. O.} } @Article { Moeck2009, title = {A two-way coupling for modeling thermoacoustic instabilities in a flat flame Rijke tube}, journal = {Proceedings of the Combustion Institute}, year = {2009}, volume = {32}, number = {1}, pages = {1199-1207}, abstract = {Thermoacoustic instabilities are a serious problem for lean premixed combustion systems. Due to different time and length scales associated with the flow field, combustion, and acoustics, numerical computations of thermoacoustic phenomena are conceptually challenging. This work presents a coupled method for the simulation of thermoacoustic instabilities in low Mach number reacting flows. The acoustics are represented by a reduced order model that can be obtained from network techniques or finite element computations. A detailed chemistry finite-difference zero Mach number solver is used for the small scale flame dynamics. Under the assumption that the pressure is continuous across the flame, the acoustic model can be reduced to a time-domain relation mapping the velocity perturbation downstream of the flame to that upstream. Closure is obtained by the flame code, which delivers the jump in velocity across the combustion zone. The method is applied to an experimental laminar premixed burner-stabilized flat flame Rijke tube, that exhibits strong thermoacoustic oscillations associated with the 5\(\lambda\)/4 mode of the geometrical set-up. In addition to the fundamental oscillation, a significant subharmonic response of the flame is observed. Results from the coupled simulation are compared to the experimental data. Good qualitative and quantitative agreement is found.}, ISSN = {1540-7489}, DOI = {10.1016/j.proci.2008.05.062}, author = {Moeck, J. P. and Oevermann, M. and Klein, R. and Paschereit, C. O. and Schmidt, H.-J.} } @Article { Guyot2009, title = {Active Combustion Control Using a Fluidic Oscillator for Asymmetric Fuel Flow Modulation}, journal = {International Journal of Flow Control}, year = {2009}, volume = {1}, number = {2}, pages = {155-166}, web_url2 = {http://multi-science.metapress.com/content/y114p22636211h45/fulltext.pdf}, ISSN = {1756-8250 (Print)}, DOI = {10.1260/175682509788913335}, author = {Guyot, D. and Paschereit, C. O. and Raghu, S.} } @Article { Bothien2009a, title = {Assessment of different actuator concepts for acoustic boundary control of a premixed combustor}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2009}, volume = {131}, number = {2}, pages = {021502 (10 pages)}, url = {http://link.aip.org/link/?GTP/131/021502/1}, publisher = {ASME}, ISSN = {0742-4795 (online), 1528-8919 (print)}, DOI = {10.1115/1.2969088}, author = {Bothien, M. R. and Moeck, J. P. and Paschereit, C. O.} } @Article { Konle2009, title = {Development of optical measurement techniques for thermo-acoustic diagnostics: Fibre-optic microphone, Rayleigh-scattering, and acoustic PIV}, journal = {International Journal of Spray and Combustion}, year = {2009}, volume = {1}, number = {2}, pages = {251-281}, abstract = {Thermo-acoustic investigations require reliable measurement techniques in hot environments for pressure, density fluctuations with a high dynamic range and acoustic particle velocity. This paper presents recent developments of optical measurement techniques in combustion diagnostics. A fibre-optic microphone based on the interferometric detection of membrane deflections was designed to measure acoustic pressure oscillations. Due to the heat resistant design, the sensor has an upper temperature limitation of approximately 970 K. Rayleigh-Scattering measurements, using the density dependent intensity of scattered light were performed in an unconfined flame with approximately 1600 K to study amplitude and phase distribution of the flame pulsation. Acoustic particle velocity can be determined applying acoustic PIV (particle image velocimetry) technique. This paper shows a way to measure simultaneously the acoustic particle velocity and the locally resolved mean flow velocity of a turbulent flow. Together these non-invasive techniques are applicable to study thermo-acoustic processes and sound generation in combustion chambers or turbines.}, web_url2 = {http://lambda.qsensei.com/content/164v7m}, author = {Konle, H. J. and Rausch, A. and Fischer, A. and Doll, U. and Willert, C. and Paschereit, C. O. and R{\"o}hle, I.} } @Article { Greenblatt2009, title = {Flap vortex management using active Gurney flaps}, journal = {AIAA Journal}, year = {2009}, volume = {47}, number = {12}, pages = {2845-2856}, DOI = {10.2514/1.41767}, author = {Greenblatt, D. and Vey, S. and Paschereit, C. O. and Meyer, R.} } @Article { Lacarelle2009b, title = {Spatiotemporal Characterization of a Conical Swirler Flow Field Under Strong Forcing}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2009}, volume = {131}, number = {3}, pages = {031504-1 (12 pages)}, url = {http://link.aip.org/link/?GTP/131/031504/1}, publisher = {ASME}, ISBN = {0742-4795}, ISSN = {0742-4795 (online), 1528-8919 (print)}, DOI = {10.1115/1.2982139}, author = {Lacarelle, A. and Faustmann, T. and Greenblatt, D. and Paschereit, C. O. and Lehmann, O. and Luchtenburg, D. M. and Noack, B. R.} } @Conference { KrugerSP2009, title = {Simulation of lean premix combustion in a swirl burner with ANSYS CFX}, year = {2009}, month = {11}, day = {18}, booktitle = {ANSYS Conference \& 27th CADFEM Users Meeting}, event_place = {Leipzig, Germany}, event_name = {ANSYS Conference \& 27th CADFEM Users Meeting}, event_date = {November 18-20, 2009}, ISBN = {3-937523-06-5}, author = {Kr{\"u}ger, O. and Spille-Kohoff, A. and Paschereit, C. O.} } @Inproceedings { Singh2009, title = {Active Control of an Incompressible Axisymmetric Jet using Flaps}, year = {2009}, booktitle = {Proceedings of the 6th International Symposium on Turbulence and Shear Flow Phenomena (TSFP6), June 22-24, Seoul, South Korea}, author = {Singh, Y. and Greenblatt, D. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Bothien2009, title = {Active control of the acoustic boundary conditions of combustion test rigs: Extension to actuators with non-linear response}, year = {2009}, number = {ASME paper GT2009-60016}, pages = {773-786}, abstract = {In the design process, new burners are generally tested in combustion test rigs. With these experiments, as well as with CFD, finite element calculations, and low-order network models, the burner's performance in the full-scale engine is sought to be predicted. Especially, information about the thermoacoustic behaviour and the emissions is very important. As the thermoacoustics strongly depend on the acoustic boundary conditions of the system, it is obvious that test rig conditions should match or be close to those of the full-scale engine. This is, however, generally not the case. Hence, if the combustion process in the test rig is stable at certain operating conditions, it may show unfavourable dynamics at the same conditions in the engine. In previous works, the authors introduced an active control scheme which is able to mimic almost arbitrary acoustic boundary conditions. Thus, the test rig properties can be tuned to correspond to those of the full-scale engine. The acoustic boundary conditions were manipulated using woofers. In the present study, an actuator with higher control authority is investigated, which could be used to apply the control scheme in industrial test rigs. The actuator modulates an air mass flow to generate an acoustic excitation. However, in contrast to the woofers, it exhibits a strong non-linear response regarding amplitude and frequency. Thus, the control scheme is further developed to account for these non-linear transfer characteristics. This modified control scheme is then applied to change the acoustic boundary conditions of an atmospheric swirl-stabilized combustion test rig. Excellent results were obtained in terms of changing the reflection coefficient to different levels. By manipulating its phase, different resonance frequencies could be imposed without any hardware changes. The non-linear control approach is not restricted to the actuator used in this study and might therefore be of use for other actuators as well.}, url = {http://link.aip.org/link/abstract/ASMECP/v2009/i48838/p773/s1}, booktitle = {Proc. ASME Turbo Expo 2009: Power for Land, Sea, and Air (GT2009), June 8-12, Orlando, Florida, USA}, ISBN = {9780791838495 (DVD), 978-0-7918-4883-8 (online)}, DOI = {10.1115/GT2009-60016}, author = {Bothien, M. R. and Paschereit, C. O.} } @Inproceedings { Oberleithner2009, title = {Control of Vortex Breakdown in Critical Swirl Regime using Azimuthal Forcing}, year = {2009}, booktitle = {MinnowbrookVI Workshop Syracuse University}, author = {Oberleithner, K. and Paschereit, C. O. and Wygnanski, I.} } @Inproceedings { Schimek2009, title = {Design of a combustion test rig with high amplitude forcing capabilities for nonlinear flame transfer function measurements}, year = {2009}, booktitle = {M. Pawelczyk and D. Bismor (Hrsg.), 16th International Congress of Sound and Vibration, Krakov, Poland}, ISBN = {978-83-60716-71-7 (CD-Rom)}, author = {Schimek, S. and Moeck, J. P. and Paschereit, C. O.} } @Inproceedings { Nayeri2009, title = {Drag Reduction on a Generic Tractor-Trailor Using Active Flow Control in Combination with solid flaps}, year = {2009}, pages = {179-191}, editor = {Browand, McCallen, Ross}, booktitle = {Lecture Notes in Applied and Computational Mechanics 41 ''The Aerodynamics of Heavy Vehicles II: Trucks, Buses and Trains''}, ISBN = {1613-7763}, author = {Nayeri, C. N. and Greenblatt, D. and Haff, J. and Paschereit, C. O. and L{\"o}fdahl, L.} } @Inproceedings { Lacarelle2009, title = {Dynamic Mixing Model of a Premixed Combustor and Validation with Flame Transfer Function Measurements}, year = {2009}, number = {AIAA paper no. AIAA-2009-986}, booktitle = {47th AIAA Aerospace Sciences Meeting including The New Horizons Forum and Aerospace Exposition, Jan. 5-8, 2009, Orlando, Florida, USA}, ISBN = {1-56347-969-9 (DVD)}, author = {Lacarelle, A. and Moeck, J. P. and Tenham, A. and Paschereit, C. O.} } @Inproceedings { Bothien2009c, title = {Experimental Validation of Linear Stability Analysis in a Premixed Combustor by Actively Tuning Its Acoustic Boundary Conditions}, year = {2009}, volume = {Volume 2: Combustion, Fuels and Emissions}, number = {ASME paper GT2009-60019}, pages = {787-798}, abstract = {Linear stability analysis by means of low-order network models is widely spread in industry and academia to predict the thermoacoustic characteristics of combustion systems. Even though a vast amount of publications on this topic exists, much less is reported on the predictive capabilities of such stability analyses with respect to real system behaviour. In this sense, little effort has been made on investigating if predicted critical parameter values, for which the combustion system switches from stability to instability, agree with experimental observations. Here, this lack of a comprehensive experimental validation is addressed by using a model-based control scheme. This scheme is able to actively manipulate the acoustic field of a combustion test rig by imposing quasi arbitrary reflection coefficients. It is employed to continuously vary the downstream reflection coefficient of an atmospheric swirl-stabilized combustion test rig from fully reflecting to anechoic. By doing so, the transient behaviour of the system can be studied. In addition to that, an extension of the common procedure, where the stability of an operating point is classified solely based on the presence of high amplitude pressure pulsations and their frequency, is given. Generally, the predicted growth rates are only compared to measurements with respect to their sign, which obviously lacks a quantitative component. In contrast to that, in this paper, validation of linear stability analysis is conducted by comparing calculated and experimentally determined linear growth rates of unstable modes. Besides this, experimental results and model predictions are also compared in terms of frequency of the least stable mode. Excellent agreement between computations from the model and experiments is found. The concept is also used for active control of combustion instabilities. By tuning the downstream reflectivity of the combustion test rig, thermoacoustic instabilities can be suppressed. the underlying mechanism is an increase of the acoustic energy losses across the system boundary.}, url = {http://link.aip.org/link/abstract/ASMECP/v2009/i48838/p787/s1}, booktitle = {Proc. ASME Turbo Expo 2009: Power for Land, Sea, and Air (GT2009), June 8-12, Orlando, Florida, USA}, ISBN = {978-0-7918-3849-5 (CD-ROM), 978-0-7918-4883-8}, DOI = {10.1115/gt2009-60019}, author = {Bothien, M. R. and Moeck, J. P. and Paschereit, C. O.} } @Inproceedings { Harr2009, title = {Feasibility study of a recuperated turboshaft-engine based on a micro-gasturbine}, year = {2009}, number = {ASME paper GT2009-59204}, pages = {55-62}, abstract = {The present paper shows the current state of a feasibility study of the University of Applied Sciences Esslingen. The intention of this study is the conversion of a model-turbine into a turboshaft-engine for variable applications, with as few as possible modifications. The shaft power of the engine is estimated on 20 kW at least. It is intended to use a recuperator to augment its efficiency. After a general introduction possible applications are discussed and the previous design-process is explained: Subsequent to the concept-phase cycle parameters were calculated and the power turbine was designed and manufactured. At present turbine tests are running. The recuperator is of counter flow type. To shorten the flow path it is mounted directly around the combustor. Currently different variations are being designed which will be optimised. The pressure loss within the exhaust manifold between power turbine and recuperator has already been reduced by simulations and tests. This will be minimised through application of a genetic optimisation software.}, url = {http://link.aip.org/link/abstract/ASMECP/v2009/i48869/p55/s1}, publisher = {ASME}, booktitle = {Proc. ASME Turbo Expo 2009: Power for Land, Sea, and Air (GT2009), June 8-12, Orlando, Florida, USA}, ISBN = {9780791838495 (DVD), 978-0-7918-4886-9 (online)}, DOI = {10.1115/GT2009-59204}, author = {Harr, C. and Paschereit, C. O. and G{\"a}rtner, U.} } @Inproceedings { Pfeifer2009, title = {Localization of Sound Sources in Combustion Chamber}, year = {2009}, volume = {XVIII}, pages = {269-291}, editor = {Schwarz, A. and Janicka, J.}, publisher = {Springer-Verlag Berlin}, booktitle = {Combustion Noise}, ISBN = {978-3-642-02037-7}, author = {Pfeifer, C. and Paschereit, C. O. and Moeck, J. P. and Enghardt, L.} } @Inproceedings { Oberleithner2009a, title = {Low Amplitude Excitation of Moderately Swirling Jets at High Reynolds Numbers}, year = {2009}, booktitle = {Proc. 47th AIAA Aerospace Sciences Meeting including The New Horizons Forum and Aerospace Exposition}, ISBN = {1-56347-969-9 (DVD)}, author = {Oberleithner, K. and Paschereit, C. O.} } @Inproceedings { Lacarelle2009a, title = {Model Based Control of Emissions and Pulsations in a Premixed Combustor Using Fuel Staging}, year = {2009}, volume = {Volume 2: Combustion, Fuels and Emissions}, number = {ASME paper GT2009-59300}, pages = {217-229}, url = {http://link.aip.org/link/abstract/ASMECP/v2009/i48838/p217/s1}, booktitle = {Proc. ASME Turbo Expo 2009: Power for Land, Sea, and Air (GT2009), June 8-12, Orlando, Florida, USA}, ISBN = {978-0-7918-4883-8}, DOI = {10.1115/gt2009-59300}, author = {Lacarelle, A. and Moeck, J. P. and Paschereit, C. O. and Gelbert, G. and King, R.} } @Inproceedings { Moeck2009a, title = {Modeling thermoacoustic instabilities in an annular Rijke tube: Asymmetric and standing and spinning modes}, year = {2009}, booktitle = {Proceedings of the 16th International Congress on Sound and Vibration, Krakow, Poland}, ISBN = {978-83-60716-71-7 (CD-Rom)}, author = {Moeck, J. P. and Paschereit, C. O.} } @Inproceedings { Guyot2009a, title = {Optical Transfer Function Measurement for a Premixed Swirl-Stabilized Flame at Atmospheric Conditions}, year = {2009}, number = {AIAA paper no. 2009-1236}, booktitle = {47th AIAA Aerospace Sciences Meeting including The New Horizons Forum and Aerospace Exposition, Jan. 5-8, 2009 , Orlando, Florida, USA}, author = {Guyot, D. and Moeck, J. P. and Paschereit, C. O. and Schuermans, B.} } @Inproceedings { Guyot2009b, title = {Optical transfer function measurements for a swirl burner at atmospheric conditions}, year = {2009}, number = {AIAA Paper 2009-5413}, web_url2 = {http://pdf.aiaa.org/preview/CDReadyMJPC09_1980/PV2009_5413.pdf}, booktitle = {Proc. 45th AIAA/ ASME/ SAE/ ASEE Joint Propulsion Conference, Denver, USA}, ISBN = {1-56347-976-1 (DVD)}, author = {Guyot, D. and Paschereit, C. O.} } @Inproceedings { Emara2009, title = {Pilot flame impact on flow fields and combustion performances in a swirl inducing burner}, year = {2009}, booktitle = {Proc. 45th AIAA/ ASME/ SAE/ ASEE Joint Propulsion Conference, Denver, USA}, ISBN = {1-56347-976-1 (DVD)}, author = {Emara, A. and Lacarelle, A. and Paschereit, C. O.} } @Inproceedings { Albrecht2009, title = {Pilot-premix flames: Higher operational flexibility in gas turbines without NOx increase}, year = {2009}, number = {ASME paper GT2009-59181}, pages = {125-135}, abstract = {A premixed pilot injection with reduced NOx formation is proposed as a fail-safe and simple control method to extend the operating range of gas turbines. Different pilot locations within the combustion chamber were chosen to see the impact of pilot injection flames on the local extinction behavior and on the NOx formation. The pilot flame injector (PFI) represents a device for premixed pilot injection and was located in the center of the swirl burner cone. Moreover, the premixed pilot could be ignited by an embedded spark plug inside the PFI so that the main flame, especially near the lean limit, can be provided with additional radicals at the lower stagnation point of the central recirculation zone. A second pilot injection was located at the combustor dump to inject the pilot fuel/air mixture axially into the shear layer between the central and side recirculation zone. It could be shown for different main air preheat temperatures and with activated PFI flame (at 110 Hz spark frequency), that the premixed pilot is the most efficient control method for local extinction prevention without CO emission increase. Also the NOx emissions keep on similar level as the baseline case. The spark plug might also be replaced by a laser ignition device. The efficiency of laser spark plugs could be already demonstrated under atmospheric conditions in Moesl2008 [1] where different ignition devices are proposed to ignite a swirl-stabilized kerosine mixture. Moreover, former tests with the PFI flame indicate also a method to control instabilities so that high amplitude of p[prime] oscillations could be suppressed.}, url = {http://link.aip.org/link/abstract/ASMECP/v2009/i48838/p125/s1}, publisher = {ASME}, booktitle = {Proc. ASME Turbo Expo 2009: Power for Land, Sea, and Air (GT2009), June 8-12, Orlando, Florida, USA}, ISBN = {978-0-7918-4883-8 (online)}, DOI = {10.1115/GT2009-59181}, author = {Albrecht, P. and Paschereit, C. O. and Bade, S. and Dinkelacker, F. and Gutmark, E. J.} } @Inproceedings { Emara2009a, title = {Planar investigation of outlet boundary conditions effect on isothermal flow fields of a swirl-stabilized burner}, year = {2009}, number = {ASME paper GT2009-59948}, pages = {707-716}, abstract = {The swirling flow velocity profiles can be strongly influenced by the outlet conditions of the combustion chamber especially at subcritical flow conditions. The effect of such changes on the mean flow or coherent structures is still unclear. It is investigated in the present work in an industrial swirl inducing burner in cold flow conditions with help of PIV. Proper orthogonal decomposition (POD) as well as acoustic measurements were used to characterize the coherent structures shed from the burner mouth. The combustor length (670, and 2020mm) and the outlet area contraction ratio (1, 0.56, 0.27, and 0.09) are varied. Major changes in the flow field are achieved when using a short combustor and the smallest contraction ratio. For this case, a central jet with streamwise velocity is added to the typical central recirculation zone. The POD analysis of the contraction ratios 1 and 0.09 for the long combustor shows that the first helical mode as well as Kelvin Helmholtz vortices are present with minor changes for both cases. At a contraction ratio of 0.09, some new structures at the jet location and near the combustor wall appear.}, url = {http://link.aip.org/link/abstract/ASMECP/v2009/i48838/p707/s1}, booktitle = {Proc. ASME Turbo Expo 2009: Power for Land, Sea, and Air (GT2009), June 8-12, Orlando, Florida, USA}, ISBN = {9780791838495 (DVD), 978-0-7918-4883-8 (online)}, DOI = {10.1115/GT2009-59948}, author = {Emara, A. and Lacarelle, A. and Paschereit, C. O.} } @Inproceedings { Bachmann2009, title = {Plasma-based active control on low Reynolds number airfoils}, year = {2009}, pages = {1-20}, booktitle = {Proc. 49th Israel Annual Conference on Aerospace Sciences, Tel Aviv, Israel}, ISBN = {9781605609836}, author = {Bachmann, M. and Paschereit, C. O. and Utehs, S. and Vey, S. and Greenblatt, D.} } @Inproceedings { Konle2009a, title = {The design and application of fiber-optic microphones for thermo-acoustic measurements}, year = {2009}, booktitle = {Proc. 15th AIAA/CEAS Aeroacoustics Conference, May 2009, Orlando, Florida, USA}, ISBN = {978-1-56347-937-0 (CD-ROM)}, author = {Konle, H. J. and R{\"o}hle, I. and Paschereit, C. O.} } @Inproceedings { Konle2009b, title = {The design and the application of fiber-optic microphones for acoustic measurements in hot environments}, year = {2009}, editor = {DEGA}, booktitle = {Proc. International Conference on Acoustics, German Acoustical Society}, ISBN = {978-3-9808659-6-8 (CD-ROM)}, author = {Konle, H. J. and R{\"o}hle, I. and Paschereit, C. O.} } @Inproceedings { Schuermans2009, title = {Thermoacoustic Modeling of a Gas Turbine Using Transfer Functions Measured at Full Engine Pressure}, year = {2009}, number = {ASME paper GT2009-59605}, pages = {503-514}, abstract = {Thermoacoustic transfer functions have been measured of a full-scale gas turbine burner operating at full engine pressure. Excitation of the high-pressure test facility was done using a siren that modulated part of the combustion airflow. Pulsation probes have been used to record the acoustic response of the system to this excitation. In addition, the flame's luminescence response was measured by multiple photomultiplier tubes and a light spectrometer. Three techniques to obtain the thermoacoustic transfer function are proposed and employed: two combined acoustical-optical technique and a purely acoustic technique. The first acoustical-optical technique uses one single optical signal capturing the chemiluminescence intensity of the flame as a measure for the heat release in the flame. It only works, if heat release fluctuations in the flame have only one contribution, e.g. equivalence ratio or mass flow fluctuations. The second acoustic-optical acoustic-optical technique makes use of the different response of the flame's luminescence at different optical wavelengths bands to acoustic excitation. It also works, if the heat release fluctuations have two contributions, e.g. equivalence ratio and mass flow fluctuation. For the purely acoustic technique, a new method was developed in order to obtain the flame transfer function, burner transfer function and flame source term from only three pressure transducer signals. The purely acoustic method could be validated by the results obtained from the acoustic-optical techniques. The acoustic and acoustic-optical methods have been compared and a discussion on the benefits and limitations of the methods is given. The measured transfer functions have been implemented into a non-linear, three-dimensional, time domain network model of a gas turbine with an annular combustion chamber. The predicted pulsation behavior shows a good agreement with pulsation measurements on a field gas turbine.}, url = {http://link.aip.org/link/abstract/ASMECP/v2009/i48838/p503/s1}, publisher = {ASME}, booktitle = {Proc. ASME Turbo Expo 2009: Power for Land, Sea, and Air (GT2009), June 8-12, Orlando, Florida, USA}, ISBN = {9780791838495 (DVD), 978-0-7918-4883-8 (online)}, DOI = {10.1115/GT2009-59605}, author = {Schuermans, B. and G{\"u}the, F. and Pennell, D. and Guyot, D. and Paschereit, C. O.} } @Inproceedings { Hoefener2009, title = {Wind tunnel experiments of a high speed train exposed to cross wind on ground and bridge configurations}, year = {2009}, booktitle = {EUROMECH COLLOQUIUM 509 ''Vehicle Aerodynamics External Aerodynamics of Railway Vehicles, Trucks, Buses and Cars'', 24-26 M{\"a}rz 2009, Berlin, Germany}, author = {Hoefener, L. and Romann, D. and Nayeri, C. N. and Tielkes, Th. and Paschereit, C. O.} } @Article { Bothien2008, title = {Active Control of the Acoustic Boundary Conditions of Combustion Test Rigs}, journal = {Journal of Sound and Vibration}, year = {2008}, volume = {318}, pages = {678-701}, ISBN = {0022-460X}, DOI = {10.1016/j.jsv.2008.04.046}, author = {Bothien, M. R. and Moeck, J. P. and Paschereit, C. O.} } @Article { Gutmark2008, title = {Combustion instability and emission control by pulsating fuel injection}, journal = {Journal of Turbomachinery}, year = {2008}, volume = {130}, number = {1}, pages = {011012 (8 pages)}, abstract = {Open-loop control methodologies were used to suppress symmetric and helical thermoacoustic instabilities in an experimental low-emission swirl-stabilized gas-turbine combustor. The controllers were based on fuel (or equivalence ratio) modulations in the main premixed combustion (premixed fuel injection (PMI)) or, alternatively, in the secondary pilot fuel. PMI included symmetric and asymmetric fuel injection. The symmetric instability mode responded to symmetric excitation only when the two frequencies matched. The helical fuel injection affected the symmetric mode only at frequencies that were much higher than that of the instability mode. The asymmetric excitation required more power to obtain the same amount of reduction as that required by symmetric excitation. Unlike the symmetric excitation, which destabilized the combustion when the modulation amplitude was excessive, the asymmetric excitation yielded additional suppression as the modulation level increased. The NOx emissions were reduced to a greater extent by the asymmetric modulation. The second part of the investigation dealt with the control of low frequency symmetric instability and high frequency helical instability by the secondary fuel injection in a pilot flame. Adding a continuous flow of fuel into the pilot flame controlled both instabilities. However, modulating the fuel injection significantly decreased the amount of necessary fuel. The reduced secondary fuel resulted in a reduced heat generation by the pilot diffusion flame and therefore yielded lower NOx emissions. The secondary fuel pulsation frequency was chosen to match the time scales typical to the central flow recirculation zone, which stabilizes the flame in the burner. Suppression of the symmetric mode pressure oscillations by up to 20 dB was recorded. High frequency instabilities were suppressed by 38 dB, and CO emissions reduced by using low frequency modulations with 10\% duty cycle.}, url = {http://link.aip.org/link/?JTM/130/011012/1}, ISBN = {0889-504X, 1528-8900}, DOI = {10.1115/1.2749292}, author = {Paschereit, C. O. and Gutmark, E. J.} } @Article { Greenblatt2008a, title = {Delta Wing Flow Control Using Dielectric Barrier Discharge Actuators}, journal = {AIAA Journal}, year = {2008}, volume = {46}, number = {6}, pages = {1554-1560}, ISBN = {0001-1452}, DOI = {10.2514/1.33808}, author = {Greenblatt, D. and Kastantin, Y. and Nayeri, C. N. and Paschereit, C. O.} } @Article { Greenblatt2008b, title = {Dielectric barrier discharge flow control at very low flight Reynolds numbers}, journal = {AIAA Journal}, year = {2008}, volume = {46}, number = {6}, pages = {1528-1541}, ISBN = {0001-1452}, DOI = {10.2514/1.33388}, author = {Greenblatt, D. and G{\"o}ksel, B. and Rechenberg, I. and Sch{\"u}le, C. Y. and Romann, D. and Paschereit, C. O.} } @Article { Pfeifer2008b, title = {Localization of Sound Sources in Combustion Chambers}, journal = {Acoustical Society of America Journal}, year = {2008}, volume = {123}, pages = {3405-+}, DOI = {10.1121/1.2934112}, author = {Pfeifer, C. and Moeck, J. P. and Enghardt, L. and Paschereit, C. O.} } @Inproceedings { Konle2008, title = {A fiber optic microphone for pressure pulsation measurements in harsh environments: first hot measurements}, year = {2008}, url = {http://in3.dem.ist.utl.pt./lxlaser2008}, booktitle = {Proc. 14th International Symposium on Applications of Laser Techniques to Fluid Mechanics, Lissabon, Portugal, Juli 2008}, author = {Konle, H. J. and R{\"o}hle, I. and Paschereit, C. O.} } @Inproceedings { Guyot2008, title = {A fluidic actuator for active combustion control}, year = {2008}, number = {paper no. GT2008-50797}, pages = {583-595}, abstract = {In this work the performance of a fluidic actuator in an active combustion control scheme is demonstrated. The actuator was tested in two different burner configurations, a bluff body burner and a generic swirl-stabilized burner, where it modulated parts of the fuel flow. The oscillation frequency was controlled by varying the inlet mass flow of the actuator. Fluidic actuators are of special interest for fuel-based active control schemes featuring high frequency fuel flow modulation, as they are much more durable then conventional valves due to the absence of fast moving parts. Hot wire measurements were performed to investigate the fluidic actuator's oscillation characteristics without combustion. The actuator was then incorporated into a bluff body burner and a swirl-stabilized burner, respectively, where it modulated parts of the fuel flow blended with nitrogen. Pressure and heat release fluctuations in the combustor were recorded and images of the flame were taken. For both burners the heat release response of the flame to fuel flow modulation was first studied during stable combustion. The spectra of the heat release signals showed a clear peak corresponding to the fluidics' oscillation frequency, thus validating the ability of the actuator to influence the combustion process. As the next step, each of the two combustors was operated at conditions that featured a strong low-frequency combustion instability when no fuel was modulated. In case of the bluff body burner applying fuel modulation resulted in attenuation of the combustion instability for some oscillation frequencies. The attenuation was highest when modulating the fuel flow in between the fundamental instability frequency and its subharmonic. Modulating the fuel flow at the subharmonic, however, resulted in an amplification of the instable mode. Also when applied to the swirl burner, the fludics' fuel flow modulation caused a significant reduction of the pressure oscillations, although the actuator could only be operated at oscillation frequencies much lower than the instability frequency due to the attached tubes. The results obtained in this work show that the fluidic actuator in use allows for fuel modulation and hence combustion control without the need for complex and fast moving parts, thus ensuring a long actuator lifetime. This makes the fluidic actuator highly appropriate for application in industrial gas turbines.}, booktitle = {Proc. of GT2008, ASME Turbo Expo 2008: Power for Land, Sea and Air, 9-13 June 2008, Berlin, Germany}, ISBN = {07918-3842-2, 978-0-7918-4313-0 (online)}, DOI = {10.1115/GT2008-50797}, author = {Guyot, D. and Paschereit, C. O. and Raghu, S.} } @Inproceedings { DepuruMohan2008, title = {Active and passive flow control of an incompressible axisymmetric jet}, year = {2008}, volume = {Volume 6: Turbomachinery, Parts A, B, and C}, number = {ASME paper GT2008-50484}, pages = {815-827}, booktitle = {ASME Turbo Expo 2008: Power for Land, Sea and Air, June 9-13, 2008, Berlin, Germany}, ISBN = {978-0-7918-4316-1}, DOI = {10.1115/gt2008-50484}, author = {Mohan, N. K. D. and Greenblatt, D. and Nayeri, C. N. and Paschereit, C. O. and Ramamurthi, P. N.} } @Inproceedings { Guyot2008a, title = {Active Combustion Control Using a Fluidic Oscillator for Asymmetric Fuel Flow Modulation}, year = {2008}, number = {AIAA paper no. 2008-4956}, booktitle = {Proc. 44th AIAA/ ASME/ SAE/ ASEE Joint Propulsion Conference \& Exhibit, Hartford, CT, USA, July 21-23, 2008}, ISBN = {978-1-56437-943-4}, author = {Guyot, D. and Bobusch, B. and Paschereit, C. O. and Raghu, S.} } @Inproceedings { Singh2008, title = {Active Control of an Incompressible Axisymmetric Jet}, year = {2008}, volume = {4}, number = {ASME paper ESDA2008-59509}, booktitle = {ASME 2008: 9th Biennial Conference on Engineering Systems Design and Analysis (ESDA2008), July 7-9, 2008 , Haifa, Israel}, ISBN = {978-0-7918-4838-8}, DOI = {10.1115/esda2008-59509}, author = {Singh, Y. and Greenblatt, D. and Depuru Mohan, N. K. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Guyot2008b, title = {Active control of combustion instability using a fluidic actuator}, year = {2008}, number = {paper no. AIAA 2008-1058}, booktitle = {Proc. 46th AIAA Aerospace Sciences Meeting and Exhibit, 7-10 January 2008, Reno, Nevada, USA}, ISBN = {978-1-56347-937-0}, author = {Guyot, D. and Taticchi Mandolini Borgia, P. and Paschereit, C. O. and Raghu, S.} } @Inproceedings { Greenblatt2008, title = {Active management of flap-edge trailing vortices}, year = {2008}, number = {paper No. AIAA 2008-4186}, note = {Online-Ver\textbackslash''ffentlichung}, booktitle = {Proc. 4th Flow Control Conference, Invited Paper, 23-26 June 2008, Seattle, Washington, USA}, ISBN = {978-1-56347-942-7}, author = {Greenblatt, D. and Yao, C. S. and Vey, S. and Paschereit, C. O. and Meyer, R.} } @Inproceedings { Bothien2008a, title = {Assessment of different actuator concepts for acoustic boundary control of a premixed combustor}, year = {2008}, number = {paper no. GT2008-50171}, pages = {57-69}, abstract = {In the design process, new burners are generally tested in combustion test rigs. With these experiments, computational fluid dynamics, and finite element calculations, the burners' performance in the full-scale engine is sought to be predicted. Especially, information about the thermoacoustic behavior and the emissions is very important. As the thermoacoustics strongly depend on the acoustic boundary conditions of the system, it is obvious that test rig conditions should match or be close to those of the full-scale engine. This is, however, generally not the case. Hence, if the combustion process in the test rig is stable at certain operating conditions, it may show unfavorable dynamics at the same conditions in the engine. In a previous paper (GT2007-27796), the authors introduced an active control scheme which is able to mimic almost arbitrary acoustic boundary conditions. Thus, the test rig properties can be tuned to correspond to those of the full-scale engine. The acoustic boundary conditions were manipulated using woofers. In the present study, proportional valves are investigated regarding their capabilities of being used in the control scheme. It is found that the test rig impedance can be tuned equally well. In contrast to the woofers, however, the valves could be used in industrial applications, as they are more robust and exhibit more control authority. Additionally, the control scheme is further developed and used to tune the test rig at discrete frequencies. This exhibits certain advantages compared to the case of control over a broad frequency band.}, booktitle = {Proc. of GT2008, ASME Turbo Expo 2008: Power for Land, Sea and Air, 9-13 June 2008, Berlin, Germany}, ISBN = {978-0-7918-4313-0 (online)}, DOI = {10.1115/GT2008-50171}, author = {Bothien, M. R. and Moeck, J. P. and Paschereit, C. O.} } @Inproceedings { Konle2008a, title = {Aufbau und Untersuchung eines erweiterten Fabryp{\'e}rot-Interferometers f{\"u}r akustische Messungen in hei{\ss}en Umgebungen}, year = {2008}, editor = {Ruck, B. and Leder, A. and Dopheide, D.}, booktitle = {Proceedings der 16. GALA-Fachtagung ''Lasermethoden in der Str{\"o}mungsmesstechnik'', 9. - 11. September 2008, Universit{\"a}t Karlsruhe, Germany}, ISBN = {978-3-9805613-4-1}, author = {Konle, H. J. and R{\"o}hle, I. and Paschereit, C. O.} } @Inproceedings { Albrecht2008, title = {Avoidance strategy for Nox emissions and flame instabilites in a swirl-stabilized combustor}, year = {2008}, number = {AIAA paper no. 2008-1058}, note = {Online-Ver{\"o}ffentlichung}, booktitle = {Proc. 46th AIAA Aerospace Sciences Meeting and Exhibit, 7-10 January 2008, Reno, Nevada, USA}, ISBN = {1-56347-937-0}, author = {Albrecht, P. and Bade, S. and Paschereit, C. O. and Gutmark, E. J.} } @Inproceedings { Lacarelle2008, title = {Control of emissions and pulsations in a premix combustor using fuel staging}, year = {2008}, number = {AIAA paper no. 2008-1058}, note = {Online-Ver{\"o}ffentlichung}, booktitle = {Proc. 46th AIAA Aerospace Sciences Meeting and Exhibit, 7-10 January 2008, Reno, Nevada, USA}, ISBN = {978-1-56347-937-9}, author = {Lacarelle, A. and Gelbert, G. and King, R. and Paschereit, C. O.} } @Inproceedings { Kaempf2008, title = {Drag reduction with AFC on a generic car model}, year = {2008}, booktitle = {Proceedings of 2nd International Conference on Jets, Wakes and Separated Flows (ICJWSF), Berlin, Germany}, author = {K{\"a}mpf, T. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Schneider2008, title = {Experimental and computational investigation of active flow control with DBD plasma actuators at low Reynolds numbers}, year = {2008}, booktitle = {Proceedings of 2nd International Conference on Jets, Wakes and Separated Flows (ICJWSF), Berlin, Germany}, author = {Schneider, T. and Sch{\"u}le, C. Y. and Greenblatt, D. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Vey2008, title = {Flap vortex management by active Gurney flaps}, year = {2008}, number = {AIAA paper no. 2008-1058}, note = {Online-Ver{\"o}ffentlichung}, booktitle = {Proc. 46th AIAA Aerospace Sciences Meeting and Exhibit, 7-10 January 2008, Reno, Nevada, USA}, ISBN = {1-56347-937-0}, author = {Vey, S. and Greenblatt, D. and Paschereit, C. O. and Meyer, R.} } @Inproceedings { Albrecht2008a, title = {Instability control by premixed pilot flames}, year = {2008}, number = {ASME paper GT2008-50255}, abstract = {Premixed flames of swirl-stabilized combustors (displaced-half-cone) are susceptible to thermo-acoustic instabilities which should be avoided under all operating conditions in order to guarantee a long service life for both stationary and aircraft gas turbines. The source of this unstable flame behavior can e.g. be found in a transition of the premix flame structure between two stationary conditions that can be easily excited by fuel fluctuations, coherent structures within the flow and other methods. Pilot flames can alleviate this issue by either improving the dynamic stability directly or by sustaining the main combustion process at operating points where instabilities are unlikely. In the present study, the impact of two different premixed pilot injection on the combustion stability is investigated. One of the pilot injector (pilot flame injector, PFI) was located upstream of the recirculation zone at the apex of the burner. The second one was a pilot ring (PR) placed at the burner outlet on the dump plane. A noticeable feature of the pilot injector was that an ignition device allowed for creating pilot premixed flames. The present investigation evidenced that these premixed pilot flames were able to suppress instabilities over a wider fuel/air ratio range than when the conventional premixed pilot injection alone. Furthermore, it was possible to prevent instabilities and maintain the flame burning near the lean blow out when a percentage of the fuel was premixed with air and injected through the pilot ring. In the mean time, NOx emissions were significantly reduced.}, booktitle = {Proc. of GT2008, ASME Turbo Expo 2008: Power for Land, Sea and Air, 9-13 June 2008, Berlin, Germany}, ISBN = {0-7018-3842-2, 978-0-7918-4313-0 (online)}, DOI = {10.1115/GT2008-50255}, author = {Albrecht, P. and Bade, S. and Lacarelle, A. and Paschereit, C. O. and Gutmark, E. J.} } @Inproceedings { Pfeifer2008, title = {Localization of combustion noise sources in enclosed flames}, year = {2008}, booktitle = {2nd International Conference on Jets, Wakes and Separated Flows, Berlin, Sep 16--19, 2008}, author = {Pfeifer, C. and Moeck, J. P. and Enghardt, L. and Paschereit, C. O.} } @Inproceedings { Pfeifer2008a, title = {Localization of sound sources in combustion chambers}, year = {2008}, note = {Online-Ver{\"o}ffentlichung}, booktitle = {34. Deutsche Jahrestagung f{\"u}r Akustik (DAGA 2008 - Deutsche Arbeitsgemeinschaft f{\"u}r Akustik, Dresden, M{\"a}rz 2008)}, ISBN = {978-2-9521105-4-9}, author = {Pfeifer, C. and Moeck, J. P. and Enghardt, L. and Paschereit, C. O.} } @Inproceedings { Pfeifer2008c, title = {Lokalisierung von Schallquellen in geschlossenen Brennkammern}, year = {2008}, booktitle = {34. Deutsche Jahrestagung f{\"u}r Akustik, Dresden, 10--13 M{\"a}rz, 2008}, author = {Pfeifer, C. and Moeck, J. P. and Enghardt, L. and Paschereit, C. O.} } @Inproceedings { Gelbert2008, title = {Model Predictive Control of Thermoacoustic Instabilities in a Swirl-Stabilized Combustor}, year = {2008}, number = {AIAA paper no. 2008-1055}, booktitle = {46th AIAA Aerospace Sciences Meeting, 7 - 10 January 2008, Reno, Nevada}, author = {Gelbert, G. and Moeck, J. P. and Bothien, M. R. and King, R. and Paschereit, C. O.} } @Inproceedings { King2008, title = {Model predictive flow control}, year = {2008}, number = {AIAA paper no. 2008-3975}, booktitle = {38th Fluid Dynamics Conference and Exhibit, June 23-26, 2008, Seattle, Washington, USA}, ISBN = {1-56347-942-7}, author = {King, R. and Aleksic, K. and Gelbert, G. and Losse, N. and Muminovic, R. and Brunn, A. and Nitsche, W. and Bothien, M. R. and Moeck, J. P. and Paschereit, C. O. and Noack, B. R. and Rist, U. and Zengl, M.} } @Inproceedings { Lacarelle2008a, title = {Spatio-temporal characterization of a conical swirler flow field under strong forcing}, year = {2008}, volume = {Volume 3: Combustion, Fuels and Emissions, Parts A and B}, number = {Paper no. GT2008-50970}, pages = {735-748}, booktitle = {Proc. of GT2008, ASME Turbo Expo 2008: Power for Land, Sea and Air, 9-13 June 2008, Berlin, Germany}, ISBN = {978-0-7918-4313-0}, DOI = {10.1115/gt2008-50970}, author = {Lacarelle, A. and Faustmann, T. and Greenblatt, D. and Paschereit, C. O. and Lehmann, O. and Luchtenburg, D. M. and Noack, B. R.} } @Inproceedings { Moeck2008, title = {Subcritical thermoacoustic instabilities in a premixed combustor}, year = {2008}, number = {paper no. 2008-2946}, booktitle = {Proc. 14th AIAA/CEAS Aeroacoustics Conference, 5-7 May 2008, Vancouver, Canada}, ISBN = {1-56347-939-7}, author = {Moeck, J. P. and Bothien, M. R. and Schimek, S. and Lacarelle, A. and Paschereit, C. O.} } @Inproceedings { Seele2008, title = {Vortex breakdown in swirling free jets. Part 1. Mean Properties of the swirled flow}, year = {2008}, booktitle = {Proceedings of 2nd International Conference on Jets, Wakes and Separated Flows (ICJWSF), Berlin, Germany}, author = {Seele, R. and Oberleithner, K. and Paschereit, C. O. and Wygnanski, I.} } @Inproceedings { Oberleithner2008, title = {Vortex breakdown in swirling free jets. Part 2. On the natural and forced instabilities}, year = {2008}, booktitle = {Proceedings of 2nd International Conference on Jets, Wakes and Separated Flows (ICJWSF), Berlin, Germany}, author = {Oberleithner, K. and Paschereit, C. O. and Wygnanski, I.} } @Article { Guyot2007, title = {Active control of combustion instability using fuel flow modulation}, journal = {Proceedings in Applied Mathematics and Mechanics (PAMM)}, year = {2007}, volume = {7}, number = {1}, pages = {4090015-4090016}, DOI = {10.1002/pamm.200700715}, author = {Guyot, D. and Bothien, M. R. and Moeck, J. P. and Paschereit, C. O.} } @Article { Greenblatt2007, title = {Active management of entrainment and streamwise vortices in an incompressible jet}, journal = {Notes on Numerical Fluid Mechanics and Multidisciplinary Design}, year = {2007}, volume = {95}, pages = {281-292}, ISBN = {978-3-540-71438-5}, author = {Greenblatt, D. and Kastantin, Y. and Singh, Y. and Nayeri, C. N. and Paschereit, C. O.} } @Article { Bothien2007b, title = {Time domain modelling and stability analysis of complex thermoacoustic systems}, journal = {Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy}, year = {2007}, volume = {221}, number = {5}, pages = {657-668}, publisher = {Professional Engineering}, ISBN = {0957-6509 (Print) 2041-2967 (Onl}, DOI = {10.1243/09576509jpe384}, author = {Bothien, M. R. and Moeck, J. P. and Lacarelle, A. and Paschereit, C. O.} } @Inproceedings { Guyot2007a, title = {Active control of combustion instability using pilot and premix fuel modulation}, year = {2007}, note = {CD-ROM/DVD}, booktitle = {14th International Congress on Sound and Vibration, Cairns, Australia, 2007}, ISBN = {978-0-733-42516-5}, author = {Guyot, D. and Roessler, M. and Bothien, M. R. and Paschereit, C. O.} } @Inproceedings { Moeck2007, title = {An Active Control Scheme for Tuning Acoustic Impedances}, year = {2007}, number = {AIAA paper no. 2007-3540}, booktitle = {13th AIAA/CEAS Aeroacoustics Conference (28th AIAA Aeroacoustics Conference), May 21-23, 2007, Rome, Italy}, author = {Moeck, J. P. and Bothien, M. R. and Paschereit, C. O.} } @Inproceedings { Moeck2007a, title = {An assessment of alternative sensor technology for transfer matrix measurements in combustors}, year = {2007}, booktitle = {Proceedings of the 14th International Congress on Sound and Vibration, 9-12 July 2007, Cairns, Australia}, ISBN = {978-0-733-42516-5}, author = {Moeck, J. P. and Konle, H. J. and Paschereit, C. O.} } @Inproceedings { Moeck2007b, title = {An asymptotically motivated two-way hydrodynamic--acoustic coupling for modeling thermoacoustic instabilities in a laminar flame Rijke tube}, year = {2007}, booktitle = {Proceedings of the 14th International Congress on Sound and Vibration, 9-12 July 2007, Cairns, Australia}, ISBN = {978-0-733-42516-5}, author = {Moeck, J. P. and Schmidt, H.-J. and Oevermann, M. and Paschereit, C. O. and Klein, R.} } @Inproceedings { Gutmark2007, title = {Combustion Noise in a Flameless Trapped Vortex Reheat Burner (FTVRB)}, year = {2007}, number = {AIAA paper no. 2007-3697}, booktitle = {13th AIAA/CEAS Aeroacoustics Conference (28th AIAA Aeroacoustics Conference), May 21-23, 2007, Rome, Italy}, author = {Gutmark, E. J. and Paschereit, C. O. and Guyot, D. and Lacarelle, A. and Moeck, J. P. and Schimek, S. and Faustmann, T. and Bothien, M. R.} } @Inproceedings { Greenblatt2007a, title = {Delta Wing Flow Control Using Dielectric Barrier Discharge Actuators}, year = {2007}, number = {AIAA paper no. 2007-4277}, publisher = {AIAA}, booktitle = {25th AIAA Applied Aerodynamics Conference, 25-28 June, Miami, FL}, author = {Greenblatt, D. and Kastantin, Y. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Lacarelle2007, title = {Effect of Fuel/Air Mixing on NOx Emissions and Stability in a Gas Premixed Combustion System}, year = {2007}, number = {AIAA paper no. 2007-1417}, booktitle = {45th AIAA Aerospace Sciences Meeting and Exhibit, Jan. 8-11, 2007, Reno, Nevada, USA}, author = {Lacarelle, A. and Moeck, J. P. and Konle, H. J. and Vey, S. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Bothien2007, title = {Experimental Validation of Linear Stability Analysis in Premixed Combustors Supported by Active Control}, year = {2007}, booktitle = {Proceedings of the 14th International Congress on Sound and Vibration, Cairns, Australia}, ISBN = {978-0-733-42516-5}, author = {Bothien, M. R. and Moeck, J. P. and Paschereit, C. O.} } @Inproceedings { Pfeifer2007, title = {Identification of Combustion Noise Sources in Enclosed Flames}, year = {2007}, booktitle = {11th CEAS/ASC Workshop of X3-Noise, 27/28 September, 2007, Istituto Superior Tecnico, Lisbon}, author = {Pfeifer, C. and Moeck, J. P. and Paschereit, C. O. and Enghardt, L.} } @Inproceedings { Bothien2007a, title = {Impedance Tuning of a Premixed Combustor Using Active Control}, year = {2007}, volume = {Volume 2: Turbo Expo 2007}, number = {ASME paper GT2007-27796}, pages = {607-617}, booktitle = {ASME Turbo Expo 2007: Power for Land, Sea, and Air (GT2007), May 14-17, 2007 , Montreal, Canada}, ISBN = {0-7918-4791-8}, DOI = {10.1115/gt2007-27796}, author = {Bothien, M. R. and Moeck, J. P. and Paschereit, C. O.} } @Inproceedings { Albrecht2007, title = {Lean blowout control using an auxiliary premixed flame in a swirl-stabilized combustor}, year = {2007}, number = {AIAA paper no. 2007-5632}, booktitle = {43rd AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, July 8-11, 2007, Cincinnati, OH, USA}, ISBN = {1492-955909}, author = {Albrecht, P. and Speck, S. and Schimek, S. and Bauermeister, F. and Paschereit, C. O. and Gutmark, E. J.} } @Inproceedings { Paschereit2007, title = {Leisere Busse}, year = {2007}, volume = {20}, number = {638}, editor = {Bundesministerium f{\"u}r Verkehr, Bau und Stadtentwicklung}, publisher = {Verkehrsblatt-Verlag, Bonn}, booktitle = {Verkehrsblatt}, ISBN = {0042-4013}, author = {Paschereit, C. O. and Moeck, J. P. and Engel, R.} } @Inproceedings { Moeck2007c, title = {Passive Control of Combustion Induced Noise in an Auxiliary Bus Heating System}, year = {2007}, booktitle = {Proceedings of the 14th International Congress on Sound and Vibration, Cairns, Australia}, ISBN = {978-0-733-42516-5}, author = {Moeck, J. P. and Engel, R. and Paschereit, C. O.} } @Inproceedings { Moeck2007d, title = {Phase-Shift Control of Combustion Instability Using (Combined) Secondary Fuel Injection and Acoustic Forcing}, journal = {Notes on Numerical Fluid Mechanics and Multidisciplinary Design (NNFM)}, year = {2007}, volume = {95}, number = {Papers contributed to the 1st Conference on ''Active Flow Control'', Sep. 27-29, 2006, Berlin, Germany}, pages = {408--421}, editor = {King, R.}, publisher = {Springer-Verlag Berlin}, booktitle = {Notes on Numerical Fluid Mechanics and Multidisciplinary Design (NNFM)}, ISBN = {978-3-540-71438-5 und 3-540-7143}, DOI = {10.1007/978-3-540-71439-2}, author = {Moeck, J. P. and Bothien, M. R. and Guyot, D. and Paschereit, C. O.} } @Inproceedings { Guyot2007b, title = {Pollutant and Noise Emissions in a Flameless Trapped-Vortex Reheat Burner (FTVRB)}, year = {2007}, number = {AIAA paper no. 2007-5630}, booktitle = {43rd AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, July 8-11, 2007, Cincinnati, OH, USA}, author = {Guyot, D. and Bothien, M. R. and Moeck, J. P. and Lacarelle, A. and Schimek, S. and Faustmann, T. and Paschereit, C. O. and Gutmark, E. J.} } @Inproceedings { Goeksel2007, title = {Pulsed Plasma Actuators for Active Flow Control at MAV Reynolds Numbers}, year = {2007}, volume = {95}, number = {Papers contributed to the 1st Conference on ''Active Flow Control'', Sep. 27-29, 2006, Berlin, Germany}, pages = {42-55}, editor = {King, R.}, publisher = {Springer Verlag, Berlin}, booktitle = {Notes on Numerical Fluid Mechanics and Multidisciplinary Design (NNFM)}, ISBN = {978-3-540-71438-5 und 3-540-7143}, DOI = {10.1007/978-3-540-71439-2}, author = {G{\"o}ksel, B. and Greenblatt, D. and Rechenberg, I. and Kastantin, Y. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Moeck2007e, title = {Two-Parameter Extremum Seeking for Control of Thermoacoustic Instabilities and Characterization of Linear Growth}, year = {2007}, number = {AIAA paper no. 2007-1416}, booktitle = {Proc. 45th AIAA Aerospace Sciences Meeting and Exhibit, January 8-11, 2007, Reno, Nevada, USA}, author = {Moeck, J. P. and Bothien, M. R. and Paschereit, C. O. and Gelbert, G. and King, R.} } @Inproceedings { Oberleithner2007a, title = {Vortex Breakdown in a Swirling Jet with Axial Forcing}, year = {2007}, number = {5010}, url = {http://hdl.handle.net/2042/15578}, publisher = {AFM, Maison de la M{\'e}canique, 39/41 rue Louis Blanc - 92400 Courbevoie}, booktitle = {18eme Congres Francais de M{\'e}canique, 27-31 Ao{\^u}t 2007, Grenoble, Colloquium C3: Stratified and Rotating Flows}, author = {Oberleithner, K. and Paschereit, C. O. and Wygnanski, I.} } @Article { Paschereit2006, title = {Combustion control by vortex breakdown stabilization}, journal = {Journal of Turbomachinery}, year = {2006}, volume = {128}, number = {4}, pages = {679-688}, author = {Paschereit, C. O. and Flohr, P. and Gutmark, E. J.} } @Article { Paschereit2006a, title = {Control of high frequency thermoacoustic pulsations by distributed vortex generators}, journal = {AIAA Journal}, year = {2006}, volume = {44}, number = {3}, pages = {550-557}, author = {Paschereit, C. O. and Gutmark, E. J.} } @Inproceedings { Bothien2006, title = {A Modular Approach for Time Domain Modelling of Complex (Thermo-)Acoustic Systems}, year = {2006}, booktitle = {Proceedings of the 13th International Conference on Modelling Fluid Flow, Budapest, Hungary}, author = {Bothien, M. R. and Moeck, J. P. and Paschereit, C. O.} } @Inproceedings { Greenblatt2006, title = {Active Management of Entrainment and Streamwise Vortices in an Incompressible Jet}, year = {2006}, booktitle = {First Berlin Conference on Active Flow Control, Berlin, Germany}, author = {Greenblatt, D. and Singh, Y. and Kastantin, Y. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Albrecht2006, title = {Characterization and Control of Lean Blowout Using Periodically Generated Flame Balls}, year = {2006}, volume = {Volume 1: Combustion and Fuels, Education}, number = {ASME paper GT2006-90340}, pages = {293-302}, booktitle = {ASME Turbo Expo 2006: Power for Land, Sea, and Air (GT2006), May 8-11, 2006 , Barcelona, Spain}, ISBN = {0-7918-4236-3}, DOI = {10.1115/gt2006-90340}, author = {Albrecht, P. and Bauermeister, F. and Bothien, M. R. and Lacarelle, A. and Moeck, J. P. and Paschereit, C. O. and Gutmark, E. J.} } @Inproceedings { Paschereit2006b, title = {Model based control of unstable reacting flows}, year = {2006}, booktitle = {Proc. Symposium in honor of Prof. I. Wygnanski, June 14-17, 2006, Eilat, Israel}, author = {Paschereit, C. O.} } @Inproceedings { Schuermans2006, title = {Non-linear combustion instabilities in annular gas-turbine combustors}, year = {2006}, booktitle = {44th AIAA Aerospace Sciences Meeting and Exhibit, January 9-12, 2006, Reno, NV, USA}, author = {Schuermans, B. and Paschereit, C. O. and Monkewitz, P.} } @Inproceedings { Goeksel2006, title = {Pulsed plasma actuation at low flight Reynolds number}, year = {2006}, booktitle = {Proc. Symposium in honor of Professor I. Wygnanski, June 14-17, 2006, Eilat, Israel}, author = {G{\"o}ksel, B. and Greenblatt, D. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Goeksel2006a, title = {Pulsed plasma for separation flow control}, year = {2006}, booktitle = {Proc. Turbulence and Interactions TI2006, May 29 - June 2, 2006, Porquerolles, France}, author = {G{\"o}ksel, B. and Greenblatt, D. and Rechenberg, I. and Singh, Y. and Nayeri, C. N. and Paschereit, C. O.} } @Inproceedings { Paschereit2006c, title = {State-space modeling of thermoacoustic systems for stability analysis and time domain simulation}, year = {2006}, series = {Vienna, Austria}, booktitle = {Proceedings of the 13th International Congress on Sound and Vibration, July 2-6, 2006, Vienna, Austria}, author = {Paschereit, C. O. and Moeck, J. P. and Bothien, M. R.} } @Inproceedings { Goeksel2006b, title = {Steady and unsteady plasma wall jets for separation and circulation control}, year = {2006}, number = {AIAA paper no. 2006-3686}, booktitle = {3rd AIAA Flow Control Conference, June 5-8, 2006, San Francisco, CA, USA}, author = {G{\"o}ksel, B. and Greenblatt, D. and Rechenberg, I. and Nayeri, C. N. and Paschereit, C. O.} } @Techreport { Nayeri2006, title = {Widerstandreduktion von Sattelz{\"u}gen durch passive Ma{\ss}nahmen}, year = {2006}, institution = {STAB Jahresbericht}, author = {Nayeri, C. N. and Z{\"u}hlke, O. and L{\"o}fdahl, L. and Paschereit, C. O.} } @Unpublished { Greenblatt2006a, title = {Pulsed Plasma Actuators for Active Flow Control at MAV Reynolds Numbers}, year = {2006}, note = {1st Conference on ''Active Flow Control'', Sep. 27-29, 2006, Berlin, Germany}, author = {Greenblatt, D. and Kastantin, Y. and Singh, Y. and Nayeri, C. N. and Paschereit, C. O.} } @Article { Bellucci2005, title = {Thermoacoustic modeling of a gas-turbine combustor equipped with acoustic dampers}, journal = {Journal of Turbomachinery}, year = {2005}, volume = {127}, number = {2}, pages = {372-379}, author = {Bellucci, V. and Schuermans, B. and Nowak, D. and Flohr, P. and Paschereit, C. O.} } @Inbook { Paschereit2005, title = {Combustion Instabilities in Gas Turbine Engines: Operational Experience, Fundamental Mechanisms, and Modeling}, year = {2005}, volume = {210}, pages = {445-479}, editor = {Lieuwen, T. C. and Yang, V.}, publisher = {Published by AIAA}, series = {Progress in Astronautics and Aeronautics}, chapter = {Implementation of instability prediction in design: ALSTOM approaches}, author = {Paschereit, C. O. and Schuermans, B. and Bellucci, V. and Flohr, P.} } @Inproceedings { Sonnenberger2005, title = {Active control of a separated flow behind a fence}, year = {2005}, booktitle = {Proc. of the International Conference on Jets, Wakes and Separated Flows, Oct. 5-8, 2005, Mie, Japan}, author = {Sonnenberger, R. and Nayeri, C. N. and Fernholz, H. H. and Paschereit, C. O.} } @Inproceedings { Paschereit2005a, title = {Combustion instability control by time delay management}, year = {2005}, booktitle = {Proc. of the Twelth International Congress on Sound and Vibration, July 11-14, 2005, Instituto Superior T{\'e}cnico, Lisbon, Portugal.}, author = {Paschereit, C. O. and Gutmark, E. J.} } @Inproceedings { Paschereit2005b, title = {Combustion instability suppression by active control of the burner mixing profile}, year = {2005}, booktitle = {Proc. of the International Conference on Jets, Wakes and Separated Flows, Oct. 5-8, 2005, Mie, Japan}, author = {Paschereit, C. O. and Schuermans, B.} } @Inproceedings { Paschereit2005c, title = {Modeling and control of combustion instabilities}, year = {2005}, booktitle = {Proc. of the Twelth International Congress on Sound and Vibration, July 11-14, 2005, Instituto Superior T{\'e}cnico, Lisbon, Portugal.}, author = {Paschereit, C. O. and Schuermans, B. and Bellucci, V.} } @Article { Bellucci2004, title = {Numerical and experimental study of a acoustic damping generated by perforated screeens with bias flow}, journal = {AIAA Journal}, year = {2004}, volume = {42}, number = {8}, pages = {1543-1549}, author = {Bellucci, V. and Paschereit, C. O. and Flohr, P.} } @Inproceedings { Schuermans2004, title = {A detailed analysis of thermoacoustic interaction mechanisms in premixed flames}, year = {2004}, number = {2004-GT-53831}, booktitle = {ASME Turbo Expo, June 14-17, 2004, Vienna, Austria}, author = {Schuermans, B. and Bellucci, V. and G{\"u}the, F. and Flohr, P. and Paschereit, C. O.} } @Inproceedings { Sonnenberger2004, title = {Closed-loop control of a reverse-flow region}, year = {2004}, volume = {X}, pages = {713-716}, editor = {Andersson, H. I. and Krogstad, P. A.}, booktitle = {Advances in Turbulence}, author = {Sonnenberger, R. and Fernholz, H. H. and Paschereit, C. O.} } @Inproceedings { Paschereit2004, title = {Control of combustion instability and emissions by burner's exit geometry modifications}, year = {2004}, booktitle = {42nd AIAA Aerospace Sciences Meeting and Exhibit, January 5-8, 2004, Reno, Nevada, USA}, author = {Paschereit, C. O. and Gutmark, E. J.} } @Inproceedings { Sonnenberger2004a, title = {Feedback control of a reverse-flow region}, year = {2004}, booktitle = {10th European Turbulence Conference (ETC10), June 29-July 2, 2004, Norwegian University of Science and Technology, Trondheim, Norway}, author = {Sonnenberger, R. and Fernholz, H. H. and Paschereit, C. O.} } @Inproceedings { Flohr2004, title = {On the use of CFD in modeling combustion dynamics}, year = {2004}, booktitle = {Proc. of CHT-04, International Symposium on Advances in Computational Heat Transfer, CHT-04-233, April 19-24, 2004, Norway}, author = {Flohr, P. and Paschereit, C. O.} } @Inproceedings { Paschereit2004a, title = {The effectiveness of passive combustion control methods}, year = {2004}, number = {2004-GT-53587}, booktitle = {ASME Turbo Expo, June 14-17, 2004, Vienna, Austria}, author = {Paschereit, C. O. and Gutmark, E. J.} } @Inproceedings { Schuermans2004a, title = {Thermoacoustic flame transfer function of a gas turbine burner in premix and pre-premix combustion}, year = {2004}, number = {AIAA paper no. 2004-456}, booktitle = {42nd AIAA Aerospace Sciences Meeting and Exhibit, January 5-8, 2004, Reno, Nevada, USA}, author = {Schuermans, B. and Bellucci, V. and Paschereit, C. O. and Flohr, P.} } @Article { Campos-Delgado2003, title = {Thermoacoustic instabilities: Modeling and control}, journal = {Transactions on Control Systems Technology}, year = {2003}, volume = {11}, number = {4}, pages = {429-447}, author = {Campos-Delgado, D. U. and Schuermans, B. and Zhou, K. and Paschereit, C. O. and Gallestey, E. and Poncet, A.} } @Inproceedings { Paschereit2003, title = {A hybrid approach to model combustion instabilities}, year = {2003}, booktitle = {Conference on Modelling Fluid Flow (CMFF'03) The 12th International Conference on Fluid Flow Technologies, September 3-6, 2003, Budapest, Hungary}, author = {Paschereit, C. O. and Schuermans, B. and Bellucci, V.} } @Inproceedings { Paschereit2003a, title = {Combustion process optimization using evolutionary algorithm}, year = {2003}, number = {2003-GT-38393}, booktitle = {ASME Turbo Expo, June 16-19, 2003, Atlanta, USA}, author = {Paschereit, C. O. and Schuermans, B. and B{\"u}che, D.} } @Inproceedings { Paschereit2003b, title = {Passive combustion control for enhanced stability and reduced emissions in a swirl-stabilized burner}, year = {2003}, booktitle = {41st AIAA Aerospace Sciences Meeting and Exhibit, January 6-9, 2003, Reno, Nevada, USA}, author = {Paschereit, C. O. and Gutmark, E. J.} } @Inproceedings { Flohr2003, title = {Steady CFD analysis for gas-turbine burner transfer functions}, year = {2003}, booktitle = {41st AIAA Aerospace Sciences Meeting and Exhibit, January 6-9, 2003, Reno, Nevada, USA}, author = {Flohr, P. and Paschereit, C. O. and Bellucci, V.} } @Inproceedings { Schuermans2003, title = {Thermoacoustic modeling and control of multi burner combustion systems}, year = {2003}, number = {2003-GT-38688}, booktitle = {ASME Turbo Expo, June 16-19, 2003, Atlanta, Georgia, USA}, author = {Schuermans, B. and Bellucci, V. and Paschereit, C. O.} } @Article { Paschereit2002b, title = {Measurement of transfer matrices and source terms of premixed flames}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2002}, month = {3}, day = {26}, volume = {124}, number = {2}, pages = {239-247}, ISSN = {0742-4795 (online), 1528-8919 (print)}, DOI = {10.1115/1.1383255}, author = {Paschereit, C. O. and Schuermans, B. and Polifke, W. and Mattson, O.} } @Article { Paschereit2002f, title = {Proportional control of combustion instabilities in a simulated gas-turbine combustor}, journal = {Journal of Propulsion and Power}, year = {2002}, volume = {18}, number = {6}, pages = {1298-1304}, author = {Paschereit, C. O. and Gutmark, E. J.} } @Inproceedings { Paschereit2002, title = {Combustion control by extended EV burner fuel lance}, year = {2002}, number = {2002-GT-30462}, booktitle = {ASME Turbo Expo, June 3-6, 2002, Amsterdam, Netherlands}, author = {Paschereit, C. O. and Flohr, P. and Kn{\"o}pfel, H. and Geng, W. and Steinbach, C. and Stuber, P. and Bengtsson, K. and Gutmark, E. J.} } @Inproceedings { Paschereit2002a, title = {Enhanced performance of a gas-turbine combustor using miniature vortex generators}, year = {2002}, volume = {29}, number = {1}, pages = {123-129}, booktitle = {Proc. of the Combustions Institute}, author = {Paschereit, C. O. and Gutmark, E. J.} } @Inproceedings { Flohr2002, title = {Mixing field analysis of a gas turbine burner}, year = {2002}, booktitle = {Proc. of IMECE, New Orleans, LA, USA}, author = {Flohr, P. and Schmitt, P. and Paschereit, C. O.} } @Inproceedings { Flohr2002a, title = {Mixing prediction in premix burners using industrial LES tools}, year = {2002}, booktitle = {ASME International Mechanical Engineering Congress and Exposition, Symposium on Computational Modeling of Industrial Combustion Systems, November 17-22, 2002, New Orleans, LO}, author = {Flohr, P. and Paschereit, C. O.} } @Inproceedings { Bellucci2002, title = {Numerical and experimental study of acoustic damping generated by acoustic screens with bias flow}, year = {2002}, booktitle = {ASME Turbo Expo, June 3-6, 2002, Amsterdam, Netherlands.}, author = {Bellucci, V. and Paschereit, C. O. and Tabacco, D. and Flohr, P.} } @Inproceedings { Nowak2002, title = {Numerical investigation of Helmholtz resonators for attanuating high frequency pulsations in industrial gas turbines}, year = {2002}, booktitle = {The 2002 International Congress and Exposition on Noise Control Engineering, August 19-21, 2002, Dearborn, MI, USA}, author = {Nowak, D. and Paschereit, C. O.} } @Inproceedings { Paschereit2002c, title = {Passive combustion control applied to premix burners}, year = {2002}, booktitle = {40th AIAA Aerospace Sciences Meeting and Exhibit, January 14-17, 2002, Reno, Nevada, USA}, author = {Paschereit, C. O. and Gutmark, E. J.} } @Inproceedings { Paschereit2002d, title = {Passive control of flow instabilities in a reacting swirling jet using vortex generators}, year = {2002}, booktitle = {9th European Turbulence Conference (ETC9), July 2-5, 2002, University of Southampton, Southampton, UK.}, author = {Paschereit, C. O. and Gutmark, E. J.} } @Inproceedings { Paschereit2002e, title = {Prediction and control of unstable gas-turbine combustion}, year = {2002}, booktitle = {9th International Congress on Sound and Vibration (ICSV9), July 8-11, 2002, Orlando, FL, USA}, author = {Paschereit, C. O.} } @Inproceedings { Paschereit2002g, title = {Suppression of thermoacoustic instabilities using passive flow control}, year = {2002}, booktitle = {The International Council of the Aeronautical Sciences (ICAS), 23rd Congress of ICAS, September 8-13, 2002, Toronto, Canada.}, author = {Paschereit, C. O. and Gutmark, E. J.} } @Inproceedings { Paschereit2002h, title = {Thermo-acoustic combustor design tools - Invited paper for panel session ''Future Trends of Combustor Technology''}, year = {2002}, booktitle = {ASME Turbo Expo, June 3-6, 2002, Amsterdam, Netherlands}, author = {Paschereit, C. O.} } @Article { Polifke2001, title = {Construktive and destructive interference of acoustic and entropy waves in a premixed combustor with a choked exit}, journal = {International Journal of Acoustics and Vibration}, year = {2001}, volume = {6}, number = {3}, pages = {135-146}, author = {Polifke, W. and Paschereit, C. O. and D{\"o}bbeling, K.} } @Article { Polifke2001a, title = {Reconstruction of acoustic transfer matrices by instationary computational fluid dynamics}, journal = {Journal of Sound and Vibration}, year = {2001}, volume = {245}, number = {3}, pages = {483-510}, author = {Polifke, W. and Poncet, A. and Paschereit, C. O. and D{\"o}bbeling, K.} } @Inproceedings { Paschereit2001, title = {Active combustion control using an evolution algorithm}, year = {2001}, booktitle = {39th AIAA Aerospace Science Meeting and Exhibit, January 8-11, 2001, Reno, Nevada, USA}, author = {Paschereit, C. O. and Schuermans, B. and Campos-Delgado, D. U.} } @Inproceedings { Paschereit2001a, title = {Messtechnische Erfassung von Brennkammerschwingungen, Koh{\"a}rente Strukturen}, year = {2001}, booktitle = {invited paper, Verbrennungsschwingungen - Thermoakustik, November 13, 2001, Universit{\"a}t der Bundeswehr, Hamburg, Haus der Technik E.V.}, author = {Paschereit, C. O.} } @Inproceedings { Paschereit2001b, title = {Model-based active instability control}, year = {2001}, booktitle = {39th AIAA Aerospace Science Meeting and Exhibit, January 8-11, 2001, Reno, Nevada, USA}, author = {Paschereit, C. O. and Schuermans, B. and Campos-Delgado, D. U.} } @Inproceedings { Paschereit2001c, title = {Modeling combustion instabilities in gas turbine combustion chambers - Invited Paper}, year = {2001}, booktitle = {39th AIAA Aerospace Science Meeting and Exhibit, January 8-11, 2001, Reno, Nevada, USA}, author = {Paschereit, C. O. and Flohr, P. and Schuermans, B.} } @Inproceedings { Bellucci2001, title = {On the use of Helmholtz resonators for damping acoustic pulsations in industrial gas turbines}, year = {2001}, booktitle = {ASME Turbo Expo, June 4-6, 2001, New Orleans, Louisiana, USA}, author = {Bellucci, V. and Paschereit, C. O. and Flohr, P. and Magni, F.} } @Inproceedings { Paschereit2001d, title = {Prediction of combustion oscillations in gas turbine combustors}, year = {2001}, number = {AIAA paper no. 2001-484}, booktitle = {39th AIAA Aerospace Science Meeting and Exhibit, January 8-11, 2001, Reno, Nevada, USA}, author = {Paschereit, C. O. and Flohr, P. and Schuermans, B.} } @Inproceedings { Bellucci2001a, title = {Thermoacoustic simulation of lean premixed flames using an enhanced time-lag model}, year = {2001}, number = {AIAA paper no. 2001-2794}, booktitle = {31st AIAA Fluid Dynamics Conference (Aeroacoustics Section), June 11-14, 2001, Anaheim, California, USA}, author = {Bellucci, V. and Paschereit, C. O. and Flohr, P. and Schuermans, B.} } @Inproceedings { Flohr2001, title = {Using CFD for time-delay modeling of premix flames}, year = {2001}, booktitle = {ASME Turbo Expo, June 4-6, 2001, New Orleans, Louisiana}, author = {Flohr, P. and Paschereit, C. O. and van Roon, B.} } @Article { Paschereit2000a, title = {Excitation of thermoacoustic instabilities by the interaction of acoustics and unstable swirling flow}, journal = {AIAA Journal}, year = {2000}, volume = {38}, pages = {1025-1034}, author = {Paschereit, C. O. and Gutmark, E. J. and Weisenstein, W.} } @Inproceedings { Paschereit2000, title = {Active combustion control in land-based gas-turbine engines}, year = {2000}, booktitle = {Topic Oriented Meeting ''Intelligent Combustion Control'' of the International Flame Research Foundation, September 25-27, 2000, Paris, France}, author = {Paschereit, C. O. and Gutmark, E. J.} } @Inproceedings { Paschereit2000b, title = {Fluid dynamic instabilities in a swirl stabilized burner and their effect on heat release fluctuations}, year = {2000}, booktitle = {Ziada, Staubli, Flow Induced Vibrations, Balkema}, author = {Paschereit, C. O. and Flohr, P. and Polifke, W. and Bockholts, M.} } @Inproceedings { Paschereit2000c, title = {Identification and control of unstable modes in an isothermal and reacting swirling jet}, year = {2000}, volume = {VIII}, pages = {101-104}, editor = {Dopazo, C.}, series = {Proceedings of the 8th European Turbulence Conference, Barcelona, Spain 27-30 June 2000}, booktitle = {Advances in Turbulence}, author = {Paschereit, C. O. and Gutmark, E. J. and Haber, L.} } @Inproceedings { Schuermans2000, title = {Investigation of thermoacoustic oscillations in combustion systems using an acoustic network model}, year = {2000}, series = {Acoustics of combustion}, booktitle = {EUROTHERM Seminar No. 67, July 5-7, 2000, Univ of Twente, Enschede, The Netherlands}, author = {Schuermans, B. and Paschereit, C. O.} } @Inproceedings { Gutmark2000, title = {Mode analysis and control in a nonreacting and reacting swirling jet}, year = {2000}, booktitle = {Bulletin of the American Physical Society / Division of Fluid Dynamics, Annual Meeting, November 19-21, 2000, Washington, DC, USA}, author = {Gutmark, E. J. and Paschereit, C. O.} } @Inproceedings { Paschereit2000d, title = {Numerical and experimental analysis of acoustically excited combustion instabilities in gas turbines}, year = {2000}, booktitle = {6th AIAA/CEAS Aeroacoustics Conference, June 12-14, 2000, Maui, Hawaii}, author = {Paschereit, C. O. and Flohr, P. and Gutmark, E. J. and Haber, L.} } @Inproceedings { Paschereit2000e, title = {Performance enhancement of gas-turbine combustor by active control of fuel injection and mixing process - theory and practice}, year = {2000}, booktitle = {Applied vehicle technology panel symposium on active control technology for enhanced performance operation capabilities of military aircraft, land vehicles and sea vehicles, North Atlantic Treaty, May 8-11, 2000, Braunschweig, Germany}, author = {Paschereit, C. O. and Gutmark, E. J. and Schuermans, B.} } @Inproceedings { Schuermans2000a, title = {Prediction of acoustic pressure spectra in combustion systems using swirl stabilized gas turbine burners}, year = {2000}, booktitle = {ASME Turbo Expo, May 13-16, 2000, Munich, Germany}, author = {Schuermans, B. and Polifke, W. and Paschereit, C. O. and van der Linden, J.} } @Inproceedings { Schuermans2000b, title = {Prediction of acoustic pressure spectra in gas turbines based on measured transfer matrices}, year = {2000}, booktitle = {ASME Turbo Expo, May 13-16, 2000, Munich, Germany}, author = {Schuermans, B. and Polifke, W. and Paschereit, C. O.} } @Inproceedings { Paschereit2000f, title = {Reduction of pressure oscillations by direct excitation of gas-turbine burner's shear layer}, year = {2000}, booktitle = {38th AIAA Aerospace Science Meeting and Exhibit, January 11-14, 2000, Reno, Nevada}, author = {Paschereit, C. O. and Gutmark, E. J. and Weisenstein, W.} } @Inproceedings { Paschereit2000g, title = {Thermoacoustic stability analysis of industrial gas turbine combustion systems}, year = {2000}, booktitle = {Proc. of the Workshop on Combustion Instabilities, December 2000, Moscow, Russia}, author = {Paschereit, C. O.} } @Article { Paschereit1999a, title = {Coherent structures in swirling flows and their role in acoustic combustion control}, journal = {Physics of Fluids}, year = {1999}, volume = {9}, pages = {2667-2678}, author = {Paschereit, C. O. and Gutmark, E. J. and Weisenstein, W.} } @Inproceedings { Paschereit1999, title = {Acoustic and fuel modulation control for reduction of thermoacoustic instabilities}, year = {1999}, booktitle = {14th International Symposium on Airbreathing EnginesSeptember 5-10, 1999, Florence, Italy}, author = {Paschereit, C. O. and Gutmark, E. J. and Weisenstein, W.} } @Inproceedings { Paschereit1999b, title = {Control of axisymmetric combustion instability modes by antisymmetric fuel injection}, year = {1999}, booktitle = {17th International Colloquium on the Dynamics of Explosions and Reactive Systems, July 25-30, 1999, Heidelberg, Germany}, author = {Paschereit, C. O. and Gutmark, E. J. and Weisenstein, W.} } @Inproceedings { Paschereit1999c, title = {Control of combustion driven oscillations by equivalence ratio modulations}, year = {1999}, booktitle = {ASME Turbo Expo, June 7-10, 1999, Indianapolis, Indiana, USA,}, author = {Paschereit, C. O. and Gutmark, E. J. and Weisenstein, W.} } @Inproceedings { Paschereit1999d, title = {Control of thermoacoustic instabilities in a premixed combustor by fuel modulation}, year = {1999}, number = {AIAA paper no. 99-0711}, booktitle = {37th AIAA Aerospace Science Meeting and Exhibit, January 11-14, 1999, Reno, Nevada}, author = {Paschereit, C. O. and Gutmark, E. J. and Weisenstein, W.} } @Inproceedings { Paschereit1999e, title = {Measurement of transfer matrices and source terms of premixed flames}, year = {1999}, booktitle = {ASME Turbo Expo, June 7-10, 1999, Indianapolis, Indiana, USA}, author = {Paschereit, C. O. and Schuermans, B. and Polifke, W. and Mattson, O.} } @Inproceedings { Schuermans1999, title = {Modeling transfer matrices of premixed flames}, year = {1999}, booktitle = {ASME Turbo Expo, June 7-10, 1999, Indianapolis, Indiana, USA}, author = {Schuermans, B. and Paschereit, C. O. and Polifke, W.} } @Inproceedings { Paschereit1999f, title = {Passive flow control applied to a gas-turbine burner: Effect on combustion and flow structure}, year = {1999}, booktitle = {Bulletin of the American Physical Society / Division of Fluid Dynamics, Annual Meeting, New Orleans, Louisiana, USA}, author = {Paschereit, C. O. and Gutmark, E. J. and Weisenstein, W.} } @Inproceedings { Gutmark1999, title = {Passive flow control applied to a gas-turbine burner: Reduction of emissions and pulsations}, year = {1999}, booktitle = {Bulletin of the American Physical Society / Division of Fluid Dynamics, Annual Meeting, New Orleans, Louisiana, USA}, author = {Gutmark, E. J. and Paschereit, C. O. and Weisenstein, W.} } @Inproceedings { Gutmark1999a, title = {Sources and control of thermoacoustic instabilities in gas-turbines}, year = {1999}, booktitle = {Sixth International Congress on Sound and Vibration, July 5-8, Lyngby, Denmark}, author = {Gutmark, E. J. and Paschereit, C. O. and Weisenstein, W.} } @Inproceedings { Paschereit1999g, title = {Suppression of Acoustically Excited Combustion Instability in Gas-Turbines}, year = {1999}, booktitle = {5th AIAA/CEAS Aeroacoustics Conference, May 10-12, Seattle, WA, USA}, author = {Paschereit, C. O. and Gutmark, E. J. and Weisenstein, W.} } @Inproceedings { Polifke1999, title = {Suppression of combustion instabilities through destructive interference of acoustic and entropy waves}, year = {1999}, booktitle = {Sixth International Congress on Sound and Vibration, July 5-8, 1999, Lyngby, Denmark}, author = {Polifke, W. and Paschereit, C. O. and D{\"o}bbeling, K.} } @Article { Paschereit1998a, title = {Control of thermoacoustic instabilities and emissions in an industrial type gas-turbine combustor}, journal = {Proceedings of the Combustion Institute}, year = {1998}, volume = {27}, pages = {1817-1824}, author = {Paschereit, C. O. and Gutmark, E. J. and Weisenstein, W.} } @Article { Polifke1998, title = {Determination of thermo-acoustic transfer matrices by experiment and computational fluid dynamics}, journal = {ERCOFTAC Bulletin}, year = {1998}, volume = {38}, author = {Polifke, W. and Paschereit, C. O.} } @Article { Paschereit1998f, title = {Structure and Control of Thermoacoustic Instabilities in a Gas-turbine Combustor}, journal = {Combustion Science and Technology}, year = {1998}, volume = {138}, pages = {213-232}, url = {http://www.informaworld.com/smpp/ftinterface~content=a777336112~fulltext=713240930~frm=content}, DOI = {10.1080/00102209808952069}, author = {Paschereit, C. O. and Gutmark, E. J. and Weisenstein, W.} } @Article { Fiedler1998, title = {Three-dimensional mixing layers and their relatives}, journal = {Experimental Thermal and Fluid Science}, year = {1998}, volume = {16}, pages = {3-21}, DOI = {10.1016/s0894-1777(97)10003-6}, author = {Fiedler, H. E. and Nayeri, C. N. and Spieweg, R. and Paschereit, C. O.} } @Inproceedings { Paschereit1998, title = {Acoustic control of combustion instabilities and emissions in a gas-turbine combustor}, year = {1998}, booktitle = {Proc. of the IEEE International Conference on Control Applications, September 1-4, 1998}, author = {Paschereit, C. O. and Gutmark, E. J. and Weisenstein, W.} } @Inproceedings { Paschereit1998b, title = {Flow-acoustic interactions as a driving mechanism for thermoacoustic instabilities}, year = {1998}, number = {AIAA paper no. 98-2274}, booktitle = {4th AIAA/ CEAS Aeroacoustics Conference, June 2-4, 1998, Toulouse, France}, author = {Paschereit, C. O. and Gutmark, E. J. and Weisenstein, W.} } @Inproceedings { Paschereit1998c, title = {Investigation of the thermoacoustic characteristics of a lean premixed gas turbine burner}, year = {1998}, number = {ASME Paper 98-GT-582}, booktitle = {ASME Turbo Expo, June 2-5, 1998, Stockholm, Sweden}, author = {Paschereit, C. O. and Polifke, W.} } @Inproceedings { Paschereit1998d, title = {Role of coherent structures in acoustic combustion control}, year = {1998}, number = {AIAA paper no. 98-2433}, booktitle = {29th AIAA Fluid Dynamics Conference, June 15-18, 1998, Albuquerque, New-Mexico}, author = {Paschereit, C. O. and Gutmark, E. J. and Weisenstein, W.} } @Inproceedings { Paschereit1998e, title = {Structure and Control of Thermoacoustic Instabilities in a Gas-turbine Combustor}, year = {1998}, number = {AIAA paper no. 98-1067}, booktitle = {36th AIAA Aerospace Science Meeting and Exhibit, January 12-15, 1998, Reno, Nevada}, author = {Paschereit, C. O. and Gutmark, E. J. and Weisenstein, W.} } @Inproceedings { Paschereit1998g, title = {Suppression of combustion instabilities by acoustic control of shear layer properties}, year = {1998}, volume = {VII}, pages = {293-296}, editor = {Frisch, U.}, publisher = {Kluwer Academics, Dordrecht/ Boston/ London}, booktitle = {Advances in Turbulence}, author = {Paschereit, C. O. and Gutmark, E. J. and Weisenstein, W.} } @Inproceedings { Gutmark1997, title = {Active Control of a Low Emission Swirl-Stabilised Combustor}, year = {1997}, booktitle = {Bulletin of the American Physical Society/ Division of Fluid Dynamics, Annual Meeting, San Francisco, California, USA}, author = {Gutmark, E. J. and Paschereit, C. O. and Weisenstein, W. and Paikert, B.} } @Inproceedings { Paschereit1997, title = {Characterization of lean premixed gas-turbine burners as acoustic multi-ports}, year = {1997}, booktitle = {Bulletin of the American Physical Society/ Division of Fluid Dynamics, Annual Meeting, San Francisco, California, USA}, author = {Paschereit, C. O. and Polifke, W.} } @Techreport { Polifke1997, title = {A universally applicable stability criterion for complex thermo-acoustic systems}, year = {1997}, number = {1313}, pages = {455-460}, institution = {VDI-Bericht}, author = {Polifke, W. and Paschereit, C. O. and Sattelmayer, T.} } @Article { Paschereit1995a, title = {Experimental investigation of subharmonic resonance in an axisymmetric jet}, journal = {Journal of Fluid Mechanics}, year = {1995}, volume = {283}, pages = {365-407}, author = {Paschereit, C. O. and Wygnanski, I. and Fiedler, H. E.} } @Techreport { Paschereit1995, title = {Dreidimensionale Strukturen in ebenen Scherschichten}, year = {1995}, institution = {DFG-Bericht}, author = {Paschereit, C. O.} } @Inproceedings { Paschereit1994a, title = {The micorophone array: a tool to reduce railway noise}, year = {1994}, booktitle = {Proc. of the International Conference on Railway Research}, author = {Paschereit, C. O. and Barsikow, B.} } @Techreport { Paschereit1994, title = {Betrachtungen zu Momenten auf umstr{\"o}mte Drosselklappen}, year = {1994}, institution = {Technical Report, akustik data, October 1994, Paris, France}, author = {Paschereit, C. O.} } @Inbook { Paschereit1993, title = {Advances in Turbulence Studies}, year = {1993}, volume = {149}, pages = {53-64}, editor = {Branover, H. and Mond, M. and Unger, Y.}, publisher = {Published by AIAA}, series = {Progress in Astronautics and Aeronautics}, chapter = {On instabilities in the axisymmmetric jet: Subharmonic resonance}, author = {Paschereit, C. O. and Wygnanski, I.} } @Inbook { Paschereit1993a, title = {Eddy Structure Identification in Free Turbulent Shear Flows}, year = {1993}, volume = {21}, pages = {115-123}, editor = {Bonnet, J. P. and Glauser, M. N.}, publisher = {Kluwer Academics, Dordrecht/ Boston/ London}, series = {Fluid Mechanics and its Applications}, chapter = {On the influence of initial parameters on subharmonic resonance in an axisymmetric jet}, author = {Paschereit, C. O. and Fiedler, H. E. and Wygnanski, I.} } @Inproceedings { Paschereit1993b, title = {Experimental investigation of the three-dimensional structure in a plane shear layer}, year = {1993}, booktitle = {Bulletin of the American Physical Society/ Division of Fluid Dynamics, 46th Annual Meeting, Albuquerque, New Mexico, USA}, author = {Paschereit, C. O. and Fiedler, H. E.} } @Article { Paschereit1992, title = {Flow visualization of interactions among large coherent structures in an axisymmetric jet}, journal = {Experiments in Fluids}, year = {1992}, volume = {12}, number = {3}, pages = {189-199}, publisher = {Springer-Verlag}, ISSN = {0723-4864 (print), 1432-1114 (online)}, DOI = {10.1007/BF00188258}, author = {Paschereit, C. O. and Oster, D. and Long, T. A. and Fiedler, H. E. and Wygnanski, I.} } @Inproceedings { Paschereit1989, title = {A detailed study of a subharmonic resonance occuring near the nozzle of an axisymmetric jet}, year = {1989}, booktitle = {Bulletin of the American Physical Society/ Division of Fluid Dynamics, 42nd Annual Meeting, Palo Alto, California, USA}, author = {Paschereit, C. O. and Wygnanski, I.} } @Inproceedings { Paschereit1989a, title = {The mixing layer between non-parallel walls}, year = {1989}, volume = {2}, pages = {467-471}, editor = {Fernholz, H. H. and Fiedler, H. E.}, publisher = {Springer Verlag, Berlin}, booktitle = {Advances in Turbulence}, author = {Paschereit, C. O. and Sch{\"u}ttpelz, M. and Fiedler, H. E.} }