% % This file was created by the Typo3 extension % sevenpack version 0.7.16 % % --- Timezone: CEST % Creation date: 2021-10-23 % Creation time: 02-51-31 % --- Number of references % 174 % @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 { VonSaldern2020a, title = {Analysis of thermoacoustic modes in can-annular combustors using effective bloch-type boundary conditions}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2020}, month = {11}, day = {19}, abstract = {Heavy-duty gas turbines are commonly designed with can-annular combustors, in which all flames are physically separated. Acoustically, however, the cans communicate via the upstream located compressor plenum, or at the downstream gaps found at the transition to the turbine inlet. In the present study, a coupling condition that is based on a Rayleigh conductivity and acoustic flux conservation is derived. It enables acoustic communication between adjacent cans, in which one-dimensional acoustic waves propagate. In addition, because can-annular systems commonly feature a discrete rotational symmetry, the acoustic field can be expressed as a Bloch-periodic wave in the azimuthal direction. We demonstrate how the coupling conditions resulting in a combustion system with $N$ cans can be expressed as an effective impedance for a single can. By means of this Bloch-type boundary condition, the thermoacoustics of a can-annular system can be analyzed considering only one can, thus reducing the size of the problem by a factor of N. Using this method, we investigate in frequency domain the effect of the coupling strength of a generic can-annular combustor consisting of 12 identical cans, which are connected at the downstream end. We describe generic features of can-annular systems and derive results on the frequency response of the cans at various Bloch numbers in the low-frequency and high-frequency limits. Furthermore, the formation of eigenvalue clusters with eigenvalues of close frequency and growth rate, but very different mode shapes is discussed.}, keywords = {Boundary-value problems, combustion chambers, acoustics, eigenvalues, waves, combustion systems, compressors, electrical conductivity, flames, frequency response, gas turbines, ode shapes, hermal conductivity,tThermoacoustics, turbines}, url = {https://asmedigitalcollection.asme.org/gasturbinespower/article/doi/10.1115/1.4049162/1091623/Analysis-of-Thermoacoustic-Modes-in-CanAnnular}, ISSN = {0742-4795}, DOI = {10.1115/1.4049162}, author = {von Saldern, J. and Orchini, A. and Moeck, J.} } @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 { 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_14092020, title = {Cluster-based network model}, journal = {Journal of Fluid Mechanics}, year = {2020}, volume = {906}, number = {21}, pages = {1-41}, abstract = {We propose an automatable data-driven methodology for robust nonlinear reduced-ordermodelling from time-resolved snapshot data. In the kinematical coarse-graining, thesnapshots are clustered into a few centroids representing the whole ensemble. Thedynamics is conceptualized as a directed network, where the centroids represent nodesand the directed edges denote possible finite-time transitions. The transition probabilitiesand times are inferred from the snapshot data. The resulting cluster-based network modelconstitutes a deterministic-stochastic grey-box model resolving the coherent-structureevolution. This model is motivated by limit-cycle dynamics, illustrated for the chaoticLorenz attractor and successfully demonstrated for the laminar two-dimensional mixinglayer featuring Kelvin-Helmholtz vortices and vortex pairing, and for an actuatedturbulent boundary layer with complex dynamics. Cluster-based network modelling opensa promising new avenue with unique advantages over other model-order reductions basedon clustering or proper orthogonal decomposition.}, keywords = {low-dimensional models, shear layers, turbulent boundary layers}, url = {https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/clusterbased-network-model/8252D04A5438ED01E624A7C41CCF81BB}, DOI = {https://doi.org/10.1017/jfm.2020.785}, author = {Li, H. and Fernex, D. and Tan, J. and M., Morzynski and Noack, B. R.} } @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 { Noack07022020, title = {Drag reduction and energy savings by spanwise travelling surface waves for flat plate flow}, journal = {Flow Turbulence Combustion}, year = {2020}, volume = {105}, pages = {125 - 157}, abstract = {Wall-resolved large-eddy simulations are performed to study the impact of spanwisetraveling transversal surface waves in zero-pressure gradient turbulent boundary layer flow.Eighty variations of wavelength, period, and amplitude of the space- and time-dependentsinusoidal wall motion are considered for a boundary layer at a momentum thickness basedReynolds number of Re= 1000 . The results show a strong decrease of friction drag of upto 26\% and considerable net power saving of up to 10\% . However, the highest net powersaving does not occur at the maximum drag reduction. The drag reduction is modeled asa function of the actuation parameters by support vector regression using the LES data.A dependence of the spanwise pressure drag on the wavelength is found. A substantialattenuation of the near-wall turbulence intensity and especially a weakening of the nearwallvelocity streaks are observed. Similarities between the current actuation techniqueand the method of a spanwise oscillating wall without any normal surface deflection arereported. In particular, the generation of a directional spanwise oscillating Stokes layer isfound to be related to skin-friction reduction.}, keywords = {Turbulent boundary layer Drag reduction Transversal traveling surface wave Large-eddy simulation ·Active flow control}, url = {https://link.springer.com/article/10.1007/s10494-020-00110-8}, ISSN = {15731987,13866184}, DOI = {https://doi.org/10.1007/s10494-020-00110-8}, author = {Albers, M. and Meysonnat, P. S. and Fernex, D. and Semaan, R. and Noack, B. R. and Schr{\"o}der, W.} } @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 { 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 { Noack_10012020, title = {Machine learning strategies applied to the control of a fluidic pinball}, journal = {Physics of Fluids}, year = {2020}, volume = {32}, number = {1}, pages = {1-13}, abstract = {The wake stabilization of a triangular cluster of three rotating cylinders is investigated. Experiments are performed at Reynolds number Re \(\sim\) 2200. Flow control is realized using rotating cylinders spanning the wind-tunnel height. The cylinders are individually connected to identical brushless DC motors. Two-component planar particle image velocimetry measurements and constant temperature hot-wire anemometry were used to characterize the flow without and with actuation. Main open-loop configurations are studied and different controlled flow topologies are identified. Machine learning control is then implemented for the optimization of the flow control performance. Linear genetic algorithms are used here as the optimization technique for the open-loop constant speed-actuators. Two different cost functions}, note = {015108}, url = {https://aip.scitation.org/doi/10.1063/1.5127202}, ISSN = {1070-6631}, DOI = {https://doi.org/10.1063/1.5127202}, author = {Raibaudo, C. and hong, P. and Noack, B. R. and Martinuzzi, R. J.} } @Article { vonSaldern2020, title = {Nonlinear interaction between clustered unstable thermoacoustic modes in can-annular combustors}, journal = {Proceedings of the Combustion Institute}, year = {2020}, abstract = {A can-annular combustor consists of a set of nominally identical cans, in which the flames burn in an essentially isolated manner. However, adjacent cans are able to communicate acoustically, which provides dynamic coupling of the entire can-annular arrangement. Recently, it was shown that the acoustic coupling is not negligible and can cause clustering of eigenfrequencies. In this study, we present a low-order modeling framework for self-excited thermoacoustic oscillations in generic can-annular combustors consisting of N identical cans. The dynamics of the flames are modeled with the nonlinear G-equation; the acoustic model accounts for plane acoustic waves inside the cans and can-to-can communication. The latter is enabled through a coupling boundary condition that is based on conservation of mass and a Rayleigh conductivity. For weak coupling between adjacent cans, the thermoacoustic feedback cycle shows clusters of linearly unstable modes of different azimuthal order, which are close in frequency and growth rate. Their interaction in the nonlinear regime is investigated using time-domain simulations. Two simulations for generic can-annular combustors consisting of 4 and 6 cans with weak acoustic coupling are discussed in this study. We observe a strong interaction between the modes, which can cause long transition times and allows modes that do not dominate the system dynamics in the linear regime to be dominant in the nonlinear regime. While the N=6 case converges to a periodic oscillation pattern with one dominant frequency, the N=4 case converges to a quasi-periodic oscillation involving modes of different azimuthal order. Moreover, we observe a synchronization of these modes. These results raise the questions whether it is possible to predict which mode(s) will dominate the system in the saturated state and under which conditions synchronization of clustered modes can occur.}, keywords = {Can-annular combustor, thermoacoustics, nonlinear interaction, weak coupling, kinematic flame model}, url = {https://www.sciencedirect.com/science/article/pii/S154074892030328X}, ISSN = {1540-7489}, DOI = {https://doi.org/10.1016/j.proci.2020.06.236}, author = {von Saldern, J. and Moeck, J. and Bianchini, A.} } @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 { 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 { Noack_20042020, title = {Upstream actuation for bluff-body wake control driven by a genetically inspired optimization}, journal = {Journal of Fluid Mechanics}, year = {2020}, volume = {893}, number = {1}, pages = {1-29}, abstract = {The control of bluff-body wakes for reduced drag and enhanced stability hastraditionally relied on the so-called direct-wake control approach. By the use ofactuators or passive devices, one can manipulate the aerodynamic loads that act on therear of the model. An alternative approach for the manipulation of the flow is to movethe position of the actuator upstream, hence interacting with an easier-to-manipulateboundary layer. The present paper comprises a bluff-body flow study via large-eddysimulations to investigate the effectiveness of an upstream actuator (positioned atthe leading edge) with regard to the manipulation of the wake dynamics and itsaerodynamic loads. A rectangular cylinder with rounded leading edges, equippedwith actuators positioned at the front curvatures, is simulated at Re = 40 000. Agenetic algorithm (GA) optimization is performed to find an effective actuation thatminimizes drag. It is shown that the GA selects superharmonic frequencies of thenatural vortex shedding. Hence, the induced disturbances, penetrating downstreamin the wake, significantly reduce drag and lateral instability. A comparison witha side-recirculation-suppression approach is also presented, the latter case beingworse in terms of reduced drag (only 8 \% drag reduction achieved), despite thetotal suppression of the side recirculation bubble. In contrast, the GA optimizedcase contributes to a 20 \% drag reduction with respect to the unactuated case. Inaddition, the large drag reduction is associated with a reduced shedding motion andan improved lateral stability.}, url = {https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/upstream-actuation-for-bluffbody-wake-control-driven-by-a-genetically-inspired-optimization/19BE0FE035B7FAB78E947B2E693B21C5}, DOI = {https://doi.org/10.1017/jfm.2020.220}, author = {Minelli, G. and Dong, T. and Noack, B. R. and Krajnovic, S.} } @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.} } @Inproceedings { Müller2020b, title = {Prediction of vortex precession in the draft tube of a model hydro turbine using mean field stability theory and stochastic modelling}, year = {2020}, address = {Lausanne, Switzerland}, booktitle = {30th Symposium on Hydraulic Machinery and Systems 2020}, organization = {IAHR}, author = {M{\"u}ller, J. and Sieber, M. and Litvinov, I. and Shtork, S. and Alekseenko, S. and Oberleithner, K.} } @Article { Tschepe2019, title = {Die Rolle der Aerodynamik bei der Energieeinsparung von modernen Schienenfahrzeugen und Hyperloop}, journal = {ETR}, year = {2019}, month = {7}, pages = {5}, abstract = {Aerodynamics referring to energy saving of modern rail vehicles and hyperloops The present article shows that aerodynamics plays an important role and has a large proportion in the rail vehicles' energy consumption. It is about 40 - 50 \% in high-speed rails or freight transports. While in the passenger transport energy savings of approximately 6 - 8 \% is possible by aerodynamics measures, the potential in freight transport shall be even 8 - 10 \%. In order to use this possibility sensibly, a greater consideration of the life-cycle-costs for freight and regional rails in the tendering process is necessary.}, author = {J., Tschepe and C. N., Nayeri and M., Hecht} } @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 { 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.} } @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.} } @Proceedings { Edwige2018, title = {Flow Control Around a SUV Simplified Vehicle}, journal = {ASME 2018 5th Joint US-European Fluids Engineering Division Summer Meeting}, year = {2018}, volume = {2 Development and Applications in Computational Fluid Dynamics; Industrial and Environmental Applications of Fluid Mechanics; Fluid Measurement and Instrumentation}, abstract = {The research on the external aerodynamics of ground vehicles can nowadays be related to sustainable development strategies, confirmed by the worldwide CO2 regulation target. Automotive manufacturers estimate that a drag reduction of 30\% contributes to 10g/km of CO2 reduction. However, this drag reduction should be obtained without constraints on the design, the safety, comfort and habitability of the passengers. Thus, it is interesting to find flow control solutions, which will remove or remote recirculation zones due to separation edges with appropriate control techniques. In automotive sales, the SUV, 4x4 and compact cars represent a large part of the market share and the study of control approaches for this geometry is practically useful. In this work, appropriate control techniques are designed to decrease the drag forces around a reduced scale SUV car benchmark called POSUV. The control techniques are based on the DMD (Dynamic Mode Decomposition) algorithms generating an optimized drag reduction procedure. It involves independent transient inflow boundary conditions for flow control actuation in the vicinity of the separation zones and time resolved pressure sensor output signals on the rear end surface of the mockup. This study, that exploits dominant flow features behind the tailgate and the rear bumper, is performed using Large Eddy Simulations on a sufficient run time scale, in order to minimize a cost function dealing with the time and space average pressure coefficient. The resulting dynamic modal decomposition obtained by these LES simulations and by wind tunnel measurements has been compared for the reference case, in order to select the most appropriate run time scale. Analysis of the numerical results shows a significant pressure increase on the tailgate, for independent flow control frequencies. Similar decomposition performed in the wake with and without numerical flow control help understanding the flow modifications in the detachment zones.}, note = {Montreal, Quebec, Canada, July 15-20, 2018}, url = {http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2710650}, series = {ASME Proceedings | 25th Symposium on Industrial and Environmental Applications of Fluid Mechanics}, organization = {ASME}, ISBN = {978-0-7918-5156-2}, DOI = {10.1115/FEDSM2018-83444}, author = {Edwige, S. and Gilotte, Ph. and Mortazavi, I. and Eulalie, Y. and Holst, D. and Nayeri, C. N. and Aider, J.-L. and Varon, E.} } @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 { 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.} } @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 { 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 { 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 { 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.} } @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 { Sieber2016, title = {Identification of unstable coherent modes in reacting swirling flows and their control}, year = {2016}, url = {http://dx.doi.org/10.2514/6.2016-1840}, publisher = {American Institute of Aeronautics and Astronautics}, series = {AIAA SciTech}, booktitle = {54th AIAA Aerospace Sciences Meeting}, author = {M. Sieber, C. O. Paschereit, K. Oberleithner} } @Inproceedings { Bölke2016, title = {Akustische Charakterisierung tieffrequent modulierter NRP-Plasmaentladungen und Kontrolle thermoakustischer Instabilit{\"a}ten}, year = {2016}, pages = {449 - 452}, abstract = {Thermoakustische Instabilit{\"a}ten stellen noch immer eine hohe Herausforderung bei der Entwicklung moderner Verbrennungssysteme dar. Durch Kopplung von W{\"a}rme- und Druckschwankungen werden teilweise so hohe Druckamplituden erzeugt, dass es zu Besch{\"a}digungen umliegender Strukturen kommen kann. Mittels passiver Ma{\ss}nahmen als auch aktiver Kontrolle wird versucht, diesen Effekt abzuschw{\"a}chen. J{\"u}ngste Arbeiten haben gezeigt, dass gepulste Nanosekunden- (NRP-) Plasmaentladungen zur Beeinflussung thermoakustischer Instabilit{\"a}ten eingesetzt werden k{\"o}nnen. Hierbei wird sowohl auf thermischer, chemischer als auch akustischer Ebene das System beeinflusst. Zur Untersuchung der jeweiligen Einflussfaktoren wurden im Rahmen dieser Arbeit die Schallerzeugungsmechanismen f{\"u}r niederfrequent modulierte NRP-Entladungen untersucht. Der Einfluss auf das akustische Feld beruht hierbei auf der kurzzeitigen W{\"a}rmefreisetzung der Entladungen. Zum Erzeugen einer maximalen tieffrequenten Schalldruckamplitude wurden mittels Burst-Modulation aus den einzelnen Entladungen periodische Signalformen erzeugt. Zur Bestimmung der akustischen Quellamplitude wurden Messungen auf Grundlage der Multi-Mikrofon-Methode (MMM) im Impedanzrohr durchgef{\"u}hrt. Untersucht wurde der Einfluss der Modulationsfrequenz, der Pulswiederholrate, der Burst- Dauer, des Elektrodenabstandes als auch der Umgebungstemperatur auf die erzeugte Schallleistung. Gemessen wurde zudem die elektrische Leistung der Entladungen. Durch Ausdruck der akustischen Quellamplitude in Abh{\"a}ngigkeit der instation{\"a}ren W{\"a}rmefreisetzungsrate lie{\ss} sich zudem auch der instantan in W{\"a}rme umgesetzte Energieanteil bestimmen. Des Weiteren wurden Untersuchungen zur D{\"a}mpfung thermoakustischer Instabilit{\"a}ten am Rijke-Rohr durchgef{\"u}hrt.}, note = {1 DVD-ROM: Illustrationen}, url = {http://publications.rwth-aachen.de/record/657934}, editor = {Michael Vorl{\"a}nder, Janina Fels}, publisher = {RWTH Aachen - Institut f{\"u}r Technische Akustik}, booktitle = {Fortschritte der Akustik: DAGA 2016}, organization = {Berlin: Deutsche Gesellschaft f{\"u}r Akustik e.V. (DEGA)}, event_place = {Aachen}, event_name = {DAGA}, event_date = {14. - 17. M{\"a}rz 2016}, ISBN = {978-3-939296-10-2, 3-939296-10-4}, reviewed = {1}, author = {B{\"o}lke, O. and Lacoste, D. and Moeck, J. P.} } @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 { 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 { Strangfeld2016, title = {High Advance-Ratio Airfoil Streamwise Oscillations: Wind Tunnel vs. Water Tunnel}, year = {2016}, number = {AIAA paper no. 2016-}, booktitle = {AIAA SciTech, 54th Aerospace Sciences Meeting, 4-8 January, San Diego, California, USA}, author = {Greenblatt, D. and Mueller-Vahl, H. and Strangfeld, C. and Medina, A. and Ol, M. V.} } @Inproceedings { Bölke2016b, title = {Sound generation and control of thermoacoustic instabilities by nanosecond plasma discharges}, year = {2016}, pages = {8}, abstract = {Sound generation by nanosecond repetitively pulsed plasma discharges is investigated experimentally. High voltage pulses of 10 nanosecond duration provide rapid heating of the air. Ahigh-frequency pulse train between 20 and 30 kHz is burst modulated to generate low-frequencycomponents. The generation of pressure waves from the modulated discharge pulse train is characterized based on acoustic measurements in an impedance tube. Different combinations of modulation frequency, electrode gap distance, modulation duty cycle and pulse repetition frequency are studied in terms of electric energy and acoustic source a plitude. The measurement results suggest that overall, the amplitude of the pressure wave components at the modulation frequency can be well estimated based on the electrical power using an a nalytical expression for acoustically compact unsteady heating. As an application of sound generation by low-frequency modulated NRP discharges, feedback control is applied to suppress the rmoacoustic instabilities in a Rijke tube. The pressure oscillation amplitude is reduced by more than two orders of magnitude when the plasma discharges are suitably synchronized with the self-excited fluctuations.}, url = {http://www.iiav.org/archives_icsv_last/2016_icsv23/content/papers/papers/full_paper_118_20160517105405844.pdf}, editor = {Prof. Konstantinos Vogiatzis, Prof. Georges Kouroussis, Prof. Malcolm Crocker, Prof. Marek Pawelczyk}, booktitle = {Proceedings of the 23rd International Congress on Sound and Vibration}, organization = {International Institute of Acoustics and Vibration (IIAV)}, ISBN = {978-960-99226-2-3}, ISSN = {2329-3675}, reviewed = {1}, author = {B{\"o}lke, O. and Lacoste, D. and Moeck, J.-P.} } @Article { Williams2015, title = {Modeling lift hysteresis with a modified Goman_Khrabrov model on pitching airfoils}, journal = {AIAA, Aerospace Research Central}, year = {2015}, month = {6}, url = {http://arc.aiaa.org/doi/pdfplus/10.2514/6.2015-2631}, ISSN = {0001-1452}, DOI = {10.2514/MFD15}, author = {Williams, D. R. and Rei{\ss}ner, F. and Greenblatt, D. and Mueller-Vahl, H. and Strangefeld, C.} } @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 { Mushyam2015, title = {A numerical investigation of laminar flow over a backward facing inclined step}, journal = {Meccanica}, year = {2015}, pages = {1--24}, abstract = {The aim of the present study is to analyze the two dimensional flow over a backward-facing-inclined step in laminar flow regime. The inspiration for the present work is derived from the fact that in automobile industry, analyzing the flow over an inclined step shall help in understanding the characteristics of the rear vehicle wake. A considerable percentage of the energy needed to propel the vehicle is dissipated by the vorticity generated in the rear of the vehicle, hence it is of utmost importance to understand the properties of the wake. In the present paper, the flow over a backward step is initially analyzed and the results are compared with the existing literature to validate the code developed. The inclined step simulations were carried out by varying different aspects of the geometry i.e. different tilts, several upstream lengths and a range of different Reynolds numbers. Critical Reynolds numbers for vortex shedding in the wake of different step inclinations have been analyzed for all cases studied. A discussion on the time-averaged drag and lift coefficients as a function of Reynolds number and for all cases undertaken, are among the results presented. Among the conclusions, it is particularly interesting to point out that the inclination angle of 15\{\textbackslashtextdegree\} was found to be the critical angle for vortex shedding, after which critical Reynolds number remains constant.}, url = {http://dx.doi.org/10.1007/s11012-015-0335-5}, ISSN = {1572-9648}, DOI = {10.1007/s11012-015-0335-5}, author = {Mushyam, A. and Bergada, J. M. and Nayeri, C. N.} } @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 { 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 { 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.} } @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 { Greenblatt2015, title = {Dielectric Barrier Discharge Plasma Flow Control on a Vertical Axis Wind Turbine}, year = {2015}, volume = {127}, pages = {71-86}, 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 = {Greenblatt, D. and M{\"u}ller-Vahl, H. and Lautman, R. and Ben-Harav, A. and Eshel, B.} } @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 { 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 { 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 { 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 { Stoehr2015a, title = {Experimental study of transient coupling of PVC formation and flame shape transition in a bi-stable turbulent swirl flame.}, year = {2015}, booktitle = {Proceedings of the 7th European Combustion Meeting (ECM 2015), Budapest, Hungary}, author = {St{\"o}hr, M. and Oberleithner, K. and Arndt, C. M. and Steinberg, A. M. and Meier, W.} } @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 { Oberleithner2015c, title = {Linear stability analysis of turbulent swirling combustor flows: impact of flow field and flame shapes on the PVC}, year = {2015}, booktitle = {Proceedings of the 7th European Combustion Meeting (ECM 2015), Budapest, Hungary}, author = {St{\"o}hr, M. and Oberleithner, K. and Arndt, C. M. and Steinberg, A. M. and Meier, W.} } @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 { 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.} } @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 { 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 { 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.} } @Conference { Moennich2014, title = {Investigation of the flow in an axial blood pump with the paint erosion method}, year = {2014}, month = {9}, day = {17}, event_place = {Rome, Italy}, event_name = {41st Annual ESAO Congress, European Society for Artificial Organs}, event_date = {Sep 17-20, 2014}, ISSN = {0391-3988}, author = {M{\"o}nnich, B. and Karakaya, T. and Bl{\"u}mel, B. and Affeld, K. and Kertzscher, U.} } @Conference { Moennich2014, title = {Analysis of shear stress volumes in the HeartWare HVAD and Heartmate II}, year = {2014}, event_place = {San Francisco, CA, USA}, event_name = {22nd Annual Congress of the International Society of Rotary Blood Pumps (ISRBP)}, event_date = {Sep 25-27, 2014}, author = {M{\"o}nnich, B. and Bl{\"u}mel, B. and Schaller, J. and Affeld, K. and Kertzscher, U.} } @Conference { Marten2014f, title = {QBlade: open source wind turbine design}, 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 = {Marten, D.} } @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 { 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 { 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 { 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 { LacosteMDLS2013, title = {Effect of Nanosecond Repetitively Pulsed Discharges on the Dynamics of a Swirl-Stabilized Lean Premixed Flame}, journal = {Journal of Engineering for Gas Turbines and Power}, year = {2013}, month = {8}, day = {30}, volume = {135}, number = {10}, pages = {101501 (7 pages)}, ISSN = {0742-4795 (online), 1528-8919 (print)}, DOI = {10.1115/1.4024961}, author = {Lacoste, D. A. and Moeck, J. P. and Durox, D. and Laux, C. O. and Schuller, T. S.} } @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 { Lacoste2012, title = {Dynamic Response of a Weakly Turbulent Lean-Premixed Flame to Nanosecond Repetitively Pulsed Discharges}, journal = {Proceedings of the Combustion Institute}, year = {2013}, volume = {34}, number = {2}, pages = {3259-3266}, DOI = {10.1016/j.proci.2012.07.017}, author = {Lacoste, D. A. and Xu, D. A. and Moeck, J. P. and Laux, C. O.} } @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 { Marten2013a, title = {Energieeffiziente Gestaltung eines gemischten Forschungs- und Gewerbe- und Wohnquartiers am Beispiel Berlin Adlershof, Teil 7: Nutzung von Windenergie}, journal = {GI - Geb{\"a}udeTechnik | InnenraumKlima}, year = {2013}, volume = {01}, publisher = {Deutscher Industrieverlag}, ISSN = {2195-643X}, author = {Marten, D.} } @Article { DuroxMBMVSC2013, title = {Flame dynamics of a variable swirl number system and instability control}, journal = {Combustion and Flame}, year = {2013}, volume = {160}, number = {9}, pages = {1729--1742}, DOI = {10.1016/j.combustflame.2013.03.004}, author = {Durox, D. and Moeck, J. P. and Bourgouin, J.-F. and Morenton, P. and Viallon, M. and Schuller, T. S. and Candel, S.} } @Article { MoeckBDSC2013, title = {Tomographic reconstruction of heat release rate perturbations induced by helical modes in turbulent swirl flames}, journal = {Experiments in Fluids}, year = {2013}, volume = {54}, number = {4}, pages = {1-17}, ISSN = {0723-4864 (print), 1432-1114 (online)}, DOI = {10.1007/s00348-013-1498-2}, author = {Moeck, J. P. and Bourgouin, J.-F. and Durox, D. and Schuller, T. S. and Candel, S.} } @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.} } @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 { Lacoste2013, title = {Effect of Nanosecond Repetitively Pulsed Discharges on the Dynamics of a Swirl-Stabilized Lean Premixed Flame}, year = {2013}, number = {ASME paper GT2013-94769}, pages = {V01AT04A054 (9 pages)}, booktitle = {Proc. ASME Turbo Expo 2013, June 3-7, San Antonio, Texas, USA}, ISBN = {978-0-7918-5510-2}, DOI = {10.1115/GT2013-94769}, author = {Lacoste, D. A. and Moeck, J. P. and Durox, D. and Laux, C. O. and Schuller, T. S.} } @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 { 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 { Bourgouin2013, title = {Self-Sustained Instabilities in an Annular Combustor Coupled by Azimuthal and Longitudinal Acoustic Modes}, year = {2013}, number = {ASME paper GT2013-95010}, pages = {V01BT04A007 (13 pages)}, booktitle = {Proc. ASME Turbo Expo 2013, June 3-7, San Antonio, Texas, USA}, ISBN = {978-0-7918-5511-9}, DOI = {10.1115/GT2013-95010}, author = {Bourgouin, J.-F. and Durox, D. and Moeck, J. P. and Schuller, T. S. and Candel, S.} } @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.} } @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 { 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 { MoeckBDSC2012, title = {Nonlinear interaction between a precessing vortex core and acoustic oscillations in a turbulent swirling flame}, journal = {Combustion and Flame}, year = {2012}, volume = {159}, number = {8}, pages = {2650-2668}, abstract = {The interaction of a helical mode with acoustic oscillations is studied experimentally in a turbulent swirl-stabilized premixed flame. In addition to a precessing vortex core (PVC), the helical mode features perturbations in the outer shear layer of the burner flow. Measurements of the acoustic pressure, unsteady velocity field and flame emission are made in different regimes including self-sustained combustion oscillations and stable regimes with and without acoustic forcing. The acoustic oscillation and the helical mode create a pronounced rotating heat release rate perturbation at a frequency corresponding to the difference of the frequencies of the two individual mechanisms. Measurements over a wide range of operating conditions for different flow rates and equivalence ratios show that while the helical mode is always present, with a constant Strouhal number, self-excited thermoacoustic oscillations exist only in a narrow region. The interaction can be observed also in cases of thermoacoustically stable conditions when external acoustic modulation is applied to the system. The evolution of the helical mode with the forcing amplitude is examined. High-speed imaging from the downstream side of the combustor demonstrates that the heat release rate perturbation associated with the nonlinear interaction of the helical mode and the acoustic oscillations produces a ''yin and yang'' -type pattern rotating with the interaction frequency in the direction of the mean swirl. At unstable conditions, the oscillation amplitude associated with the interaction is found to be significantly stronger in the heat release rate than in the velocity signal, indicating that the nonlinear interaction primarily occurs in the flame response and not in the aerodynamic field. The latter is, however, generally possible as is demonstrated under non-reacting conditions with acoustic forcing. Based on a second-order analysis of the G-equation, it is shown that the nonlinear flame dynamics necessarily generate the observed interaction component if the flame is simultaneously perturbed by a helical mode and acoustic oscillations.}, url = {http://www.sciencedirect.com/science/article/pii/S0010218012001216}, DOI = {10.1016/j.combustflame.2012.04.002}, author = {Moeck, J. P. and Bourgouin, J.-F. and Durox, D. and Schuller, T. S. and Candel, S.} } @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.} } @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 { 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.} } @Conference { Marten2012, title = {Wind Turbine Design and Analysis \& Micrositing for Small Wind Turbines in Urban Areas}, year = {2012}, booktitle = {Summer School 2012 - Meeting the Challenges of Advanced Energy Systems for the Futue, Indo-German Center for Sustainability, Berlin, EUREF Campus, 14.07.2012}, author = {Marten, D.} } @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 { Moeck2012b, title = {Investigation of precessing-vortex-core--flame interaction based on tomographic reconstruction techniques}, year = {2012}, number = {ASME paper GT2012-69626}, pages = {1213-1224 (12 pages)}, booktitle = {Proc. ASME Turbo Expo 2012, June 11-15, Bella Center, Copenhagen, Denmark}, ISBN = {978-0-7918-4468-7}, DOI = {10.1115/GT2012-69626}, author = {Moeck, J. P. and Bourgouin, J.-F. and Durox, D. and Schuller, T. S. and Candel, S.} } @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 { 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 { 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 { 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.} } @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 { 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 { 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 { 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.} } @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 { 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 { 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 { 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 { 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 { 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.} } @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 { 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 { 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.} } @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 { 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 { 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 { 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.} } @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 { 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 { 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 { 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 { 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 { 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 { 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.} } @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 { 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 { 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 { 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 { 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 { 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 { 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 { 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 { 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 { 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.} } @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.} } @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 { 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.} }