This file was created by the Typo3 extension sevenpack version 0.7.16 --- Timezone: CET Creation date: 2023-01-27 Creation time: 09-32-08 --- Number of references 568 article Soto-Valle2022 eawe, Wind Energ. Sci., 2022 3 15 7 585 – 602 This study describes the impact of postprocessing methods on the calculated parameters of tip vortices of a wind turbine model when tested using particle image velocimetry (PIV). Several vortex identification methods and differentiation schemes are compared. The chosen methods are based on two components of the velocity field and their derivatives. They are applied to each instantaneous velocity field from the dataset and also to the calculated average velocity field. The methodologies are compared through the vortex center location, vortex core radius and jittering zone. Results show that the tip vortex center locations and radius have good comparability and can vary only a few grid spacings between methods. Conversely, the convection velocity and the jittering surface, defined as the area where the instantaneous vortex centers are located, vary between identification methods. Overall, the examined parameters depend significantly on the postprocessing method and selected vortex identification criteria. Therefore, this study proves that the selection of the most suitable postprocessing methods of PIV data is pivotal to ensure robust results. https://doi.org/10.5194/wes-7-585-2022 R.Soto-Valle S.Cioni S.Bartholomay M.Manolesos C. N.Nayeri A.Bianchini C. O.Paschereit article 10.1115/1.4052087 Journal of Engineering for Gas Turbines and Power 2022 2 21 144 5 {Machine learning and automatized routines for parameter optimization have experienced a surge in development in the past years, mostly caused by the increasing availability of computing capacity. Gradient-free optimization can avoid cumbersome theoretical studies as input parameters are purely adapted based on output data. As no knowledge about the objective function is provided to the algorithms, this approach might reveal unconventional solutions to complex problems that were out of scope of classical solution strategies. In this study, the potential of these optimization methods on thermoacoustic problems is examined. The optimization algorithms are applied to a generic low-order thermoacoustic can-combustor model with several fuel injectors at different locations. We use three optimization algorithms – the well established downhill simplex method, the recently proposed explorative gradient method, and an evolutionary algorithm – to find optimal fuel distributions across the fuel lines while maintaining the amount of consumed fuel constant. The objective is to have minimal pulsation amplitudes. We compare the results and efficiency of the gradient-free algorithms. Additionally, we employ model-based linear stability analysis to calculate the growth rates of the dominant thermoacoustic modes. This allows us to highlight general and thermoacoustic-specific features of the optimization methods and results. The findings of this study show the potential of gradient-free optimization methods on combustor design for tackling thermoacoustic problems, and motivate further research in this direction.} 051004 https://doi.org/10.1115/1.4052087 0742-4795 10.1115/1.4052087 M.Reumschüssel J.von Saldern Y.Li C. O.Paschereit A.Orchini article Noack2021 Physics of Fluids 2021 9 1 33 5 33 For over a century, reduced order models (ROMs) have been a fundamental discipline of theoretical fluid mechanics. Early examples include Galerkin models inspired by the Orr–Sommerfeld stability equation and numerous vortex models, of which the von Karman vortex street is one of the most prominent. Subsequent ROMs typically relied on first principles, like mathematical Galerkin models, weakly nonlinear stability theory, and two- and three-dimensional vortex models. Aubry et al. [J. Fluid Mech. 192, 115–173 (1988)] pioneered the data-driven proper orthogonal decomposition (POD) modeling. In early POD modeling, available data were used to build an optimal basis, which was then utilized in a classical Galerkin procedure to construct the ROM, but data have made a profound impact on ROMs beyond the Galerkin expansion. In this paper, we take a modest step and illustrate the impact of data-driven modeling on one significant ROM area. Specifically, we focus on ROM closures, which are correction terms that are added to the classical ROMs in order to model the effect of the discarded ROM modes in under-resolved simulations. Through simple examples, we illustrate the main modeling principles used to construct the classical ROMs, motivate and introduce modern ROM closures, and show how data-driven modeling, artificial intelligence, and machine learning have changed the standard ROM methodology over the last two decades. Finally, we outline our vision on how the state-of-the-art data-driven modeling can continue to reshape the field of reduced order modeling. https://doi.org/10.1063/5.0061577 online 10.1063/5.0061577 S.Ahmed S.Pawar O.San A.Rasheed T.Iliescu B. R.Noack article Humbert2021 2021 6 143 6 10 Thermoacoustic oscillations in axisymmetric annular combustors are generally coupled by degenerate azimuthal modes, which can be of standing or spinning nature. Symmetry breaking due to the presence of a mean azimuthal flow splits the degenerate thermoacoustic eigenvalues, resulting in pairs of counter-spinning modes with close but distinct frequencies and growth rates. In this study, experiments have been performed using an annular system where the thermoacoustic feedback due to the flames is mimicked by twelve identical electro-acoustic feedback loops. The mean azimuthal flow is generated by fans. We investigate the standing/spinning nature of the oscillations as a function of the azimuthal Mach number for two types of initial states and how the stability of the system is affected by the mean azimuthal flow. It is found that spinning, standing, or mixed modes can be encountered at very low Mach number, but increasing the mean velocity promotes one spinning direction. At sufficiently high Mach number, only spinning modes are observed in the limit cycle oscillations. In some cases, the initial conditions have a significant impact on the final state of the system. It is found that the presence of a mean azimuthal flow increases the acoustic damping. This has a beneficial effect on stability: it often reduces the amplitude of the self-sustained oscillations, and can even suppress them in some cases. However, we observe that the suppression of a mode due to the mean flow may destabilize another one. We discuss our findings in relation to an existing low-order model. GTP-20-1401 thermoacoustic oscillations, electroacoustic feedback, annular combustor, azimuthal mean flow, acoustic damping https://doi.org/10.1115/1.4048693 English doi.org/10.1115/1.4048693 S.Humbert J.Moeck A.Orchini C. O.Paschereit article Neumann2021 Applied Thermal Engineering 2021 196 The constant pressure combustion of the Joule cycle is a dominant source of losses in gas turbines. One possible improvement is pressure gain combustion through pulse detonation combustion. However, the total pressure increase is the result of a transient periodic process that can adversely affect the performance of adjoining turbo components. The thermodynamic benefits of pressure gain combustion can thus be undermined by low efficiencies of compressor and turbine. In order to account for such unsteady effects early in the design process, suitable methods are essential. Given 3D-CFD simulations’ undue computational demands, an approach with low computation resources is required for first-order estimates. This paper introduces such an approach based on a 1D-Euler method and demonstrates its applicability. A compressor is simulated with 3D-CFD, which serves as a reference, as well as with the 1D-Euler code employing unsteady outlet boundary conditions that approximate those encountered with pulse detonation combustion. The findings suggest that the 1D-Euler code is able to accurately capture the transient compressor behaviour. Though the relative pressure amplitude at the compressor outlet of 3.6% is attenuated by 90% up to the compressor inlet, it still results in a compressor isentropic efficiency loss of 0.8 percentage points. Pressure gain combustion, unsteady compressor simulation 1D-Euler https://doi.org/10.1016/j.applthermaleng.2021.117223 10.1016/j.applthermaleng.2021.117223 N.,Neumann M.Asli N.Garan D.Peitsch P.Stathopoulos article Perez-Becker2021 Wind Energy Science 2021 6 3 791 - 814 Active trailing edge flaps are a promising technology that can potentially enable further increases in wind turbine sizes without the disproportionate increase in loads, thus reducing the cost of wind energy even further. Extreme loads and critical deflections of the blade are design-driving issues that can effectively be reduced by flaps. In this paper, we consider the flap hinge moment as a local input sensor for a simple flap controller that reduces extreme loads and critical deflections of the DTU 10 MW Reference Wind Turbine blade. We present a model to calculate the unsteady flap hinge moment that can be used in aeroelastic simulations in the time domain. This model is used to develop an observer that estimates the local angle of attack and relative wind velocity of a blade section based on local sensor information including the flap hinge moment of the blade section. For steady wind conditions that include yawed inflow and wind shear, the observer is able to estimate the local inflow conditions with errors in the mean angle of attack below 0.2∘ and mean relative wind speed errors below 0.4 %. For fully turbulent wind conditions, the observer is able to estimate the low-frequency content of the local angle of attack and relative velocity even when it is lacking information on the incoming turbulent wind. We include this observer as part of a simple flap controller to reduce extreme loads and critical deflections of the blade. The flap controller's performance is tested in load simulations of the reference turbine with active flaps according to the IEC 61400-1 power production with extreme turbulence group. We used the lifting line free vortex wake method to calculate the aerodynamic loads. Results show a reduction of the maximum out-of-plane and resulting blade root bending moments of 8 % and 7.6 %, respectively, when compared to a baseline case without flaps. The critical blade tip deflection is reduced by 7.1 %. Furthermore, a sector load analysis considering extreme loading in all load directions shows a reduction of the extreme resulting bending moment in an angular region covering 30∘ around the positive out-of-plane blade root bending moment. Further analysis reveals that a fast reaction time of the flap system proves to be critical for its performance. This is achieved with the use of local sensors as input for the flap controller. A larger reduction potential of the system is identified but not reached mainly because of a combination of challenging controller objectives and the simple controller architecture. https://doi.org/10.5194/wes-6-791-2021 doi.org/10.5194/wes-6-791-2021 S.Perez-Becker D.Marten C. O.Paschereit article Soto-Valle2021 AIAA 2021 2021 1413 Vortex generators (VGs) are often used to optimize the flow on wind turbine rotor blades, enhancing the annual energy production between 1-3% with particular focus on the underperforming aerodynamics in the blades root zone. This has generated great interest among the scientific community, proposing new geometries, besides the common rectangular and triangular layouts. These have been tested on 2D experimental setups and computational approaches, showing lower drag penalties and improved glide ratios. This paper presents an experimental comparison between three VG geometries: rectangular, triangular and Clark-Y shaped. The VGs are mounted on a research scale wind turbine model, operated in the wind tunnel of the Technische Universität Berlin. The performance is analyzed at different operational conditions by means of blade surface pressure and root bending moments. 11 – 15 & 19 – 21 January. 2021 https://arc.aiaa.org/doi/10.2514/6.2021-1413 10.2514/6.2021-1413 R.Soto-Valle S.Bartholomay M.Manolesos C. N.Nayeri C. O.,Paschereit article Soto-Valle_2021 ATI 2021 2021 312 12 Wind Energy is substantially growing in recent years and is now one of the most competitive renewable energy sources on the market. To further foster the growth of this energy source, increasing effort is put into building accurate numerical models. Most models compute the loads acting on the turbine as a dependence of some sort to the angle of attack (AoA). Accurate AoA measurements would allow for comparison with experiments and would be of great benefit for the improvement of numerical models and the investigations of aerodynamic phenomena such as stall delay. However, the determination of the angle of attack during operation is troublesome to the present day. In addition to what was already mentioned, the AoA is key to evaluate loads acting on the wind turbine and assessing experiments, computational models, and aeroelastic models. This paper proposes a simple comparative method to estimate the AoA based on pressure distributions. The proposed method is tested using data from different numbers of pressure taps placed on the Berlin Research Turbine (BeRT) at the Hermann Föttinger Institut of the Technische Universität Berlin. The predicted results are in line with those from other methods while the operating conditions to which the model can be applied are improved. id.08003 76th Italian National Congress ATI (ATI 2021) https://www.e3s-conferences.org/articles/e3sconf/abs/2021/88/e3sconf_ati2021_08003/e3sconf_ati2021_08003.html eISSN: 2267-1242 doi.org/10.1051/e3sconf/202131208003 R.Soto-Valle S.Noci F.Papi S.Bartholomay C. N.Nayeri C. O.Paschereit A.Bianchini article Sieber2021 International Journal of Heat and Fluid Flow 2021 90 In an experimental investigation, the stochastic dynamics of the global mode in a turbulent swirling jet are considered. From the application of the swirling jet in gas turbine combustors, it was observed that a specific density gradient in the flow leads to a suppression of the global mode. This phenomenon was replicated in a generic swirling jet using an electrical heating coil placed inside the breakdown bubble. In the present investigation, the dynamics of the global mode obtained from PIV and pressure measurements are analysed using a stochastic reduced-order model to describe the instability. The stochastic model is necessary to explain the interaction between the deterministic dynamics of the global mode and the perturbations by the background turbulence. The calibration of the stochastic model provides the amplification rate of the global mode that defines the transition of the flow, dependent on the swirling strength and the density difference. The spatial structure of the global mode is further invstigated from Lagrangian coherent structures of the flow field which are computed from the 3D time-resolved velocity field reconstruction based on planar PIV measurements. The Lagrangian visualisations and schlieren visualisations are used to explain the absence of the density effects on the global mode at larger Reynolds numbers. The analysis gives a detailed view of the stochastic dynamics of a hydrodynamic instability in a turbulent flow. swirling jet global mode hydrodynamic instability stochastic model Lagrangian coherent structures finite time Lyapunov exponent flow visualisation https://doi.org/10.1016/j.ijheatfluidflow.2021.108820 10.1016/j.ijheatfluidflow.2021.108820 M.Sieber C. O.Paschereit K.Oberleithner article Perez-Becker2021 Energies 2021 14 3 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. wind energy; wind turbine control; load mitigation; individual pitch control; lifting line free vortex wake; vortex methods https://www.mdpi.com/1996-1073/14/3/783 S.Perez-Becker D.Marten C. N.Nayeri C. O.Paschereit article Lommel2021 Indoor Air 2021 31 6 1860--1873 The SARS-CoV-2 pandemic has created a great demand for a better understanding of the spread of viruses in indoor environments. A novel measurement system consisting of one portable aerosol-emitting mannequin (emitter) and a number of portable aerosol-absorbing mannequins (recipients) was developed that can measure thespread of aerosols and droplets that potentially contain infectious viruses. The emissionof the virus from a human is simulated by using tracer particles solved in water. The recipients inhale the aerosols and droplets and quantify the level of solved tracer particles in their artificial lungs simultaneously over time. The mobile system can be arranged in a large variety of spreading scenarios in indoor environments and allows for quantification of the infection probability due to airborne virus spreading. This study shows the accuracy of the new measurement system and its ability to compare aerosol reduction measures such as regular ventilation or the use of a room air purifier. aerosol, infection transmission, measurement system, respiratory droplets, virus spread https://www.researchgate.net/publication/352223190_Novel_measurement_system_for_respiratory_aerosols_and_droplets_in_indoor_environments 10.1111/ina.12860 M.Lommel V.Froese M.Sieber M.Jentzsch T.Bierewirtz Ü.Hasirci T.Rese J.Seefeldt S.Schimek U.Kertzscher C. O.Paschereit article Barholomay2021 eawe, Wind Energy Science 2021 6 221 - 245 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 D 30% chordwise extension. Inflow disturbances are created by a two-dimensional active grid. The Reynolds number is Re D 290000, and reduced frequencies of k D 0:07 up to k D 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 D 0:192. ttps://doi.org/10.5194/wes-6-221-2021 doi.org/10.5194/wes-6-221-2021 S.Bartholomay T.Wester S.Perez-Becker S.Konze C.Menzel M.Hölling A.Spickenheuer J.Peinke C. N.Nayeri C. OPaschereit KilianOberleithner K. incollection Sieber-2021 2021 267 153 - 158 The observation of a Hopf bifurcation in fluid dynamics is commonly associated with the occurrence of a global hydrodynamic instability. The increase of a control parameter above a critical value causes a change from a stable to an unstable flow condition. This behaviour is well understood for the occurrence of instabilities in laminar flows. In turbulent flows, however, the occurrence of hydrodynamic instabilities is similarly observed but less clear. The current work examines the use of stochastic models to describe the supercritical Hopf bifurcation of the global mode in a turbulent swirling jet. The consideration of the interaction between the global mode and the stochastic turbulent perturbations allows a consistent description of the experimental observations. This opens up extensive possibilities for describing and interpreting the occurrence of hydrodynamic instabilities in turbulent flows. iTi 2021: Progress in Turbulence IX https://link.springer.com/chapter/10.1007/978-3-030-80716-0_20 Ramis, Ö. and Talamelli, A. and Peinke, J. and Oberlack, M. Springer

Cham

Springer eBook Collection Springer Proceedings in Physics 10.1007/978-3-030-80716-0_20 M.Sieber C. O.Paschereit K.Oberleithner proceedings Humbert_2021 Science Direct, Elsevier 2021 38 4 6085-6093 Self-excited pressure oscillations can occur in combustion systems due to the thermoacoustic coupling between the unsteady acoustics and flame heat release fluctuations. Usually, the knowledge of a Flame Transfer Function is used to predict the onset of thermoacoustic instabilities. However, it is also possible to take advantage of it to model a flame response and study experimentally thermoacoustic phenomena without flames. This is exploited in the present study, in which a novel annular setup for the study of thermoacoustics in annular combustors is presented. The thermoacoustic feedback is replaced by electroacoustic feedback. The pressure fluctuations, measured by a microphone, are delayed and filtered and then sent to a loudspeaker, which produces acoustic perturbations, closing the loop. Each flame model parameter can be varied in a flexible way, which allows to choose combinations of parameters that generate modal behaviours of interest in the experiments. For example, this setup can trigger on demand various configurations which exhibit multiple unstable modes, leading to diverse modal competition scenarios. This allows to assess the multi-input Describing Function method, which is used to predict the frequency and amplitude of each mode contributing to thermoacoustic oscillations, when multiple modes are linearly unstable. The experimental validation of predictions from this method, which can be somewhat cumbersome and expensive in the presence of flames, is facilitated by this setup, in which all parameters and boundary conditions are well known and the noise remains negligible. Prediction uncertainties connected to approximations intrinsic of this method when operating in the vicinity of bifurcation points are also discussed. Thermoacoustic oscillationsAnnular combustorElectroacoustic feedbackFlame multi-input Describing FunctionNonlinear modal coupling https://doi.org/10.1016/j.proci.2020.06.154 Elsevier Proceedings of the Combustion Instittue doi.org/10.1016/j.proci.2020.06.154 S.Humbert F.Gensini A.Andreini C. O.Paschereit A.Orchini proceedings 10.1115/GT2021-59071 2021 Volume 3A: Combustion, Fuels, and Emissions {In gas turbine combustion systems, the reduction of emissions of harmful combustion by-products is a main development goal. This study provides a methodology to model NOX emissions effectively for varying levels of pilot fuel flows at different operational points. It combines one-dimensional flame simulations using detailed chemistry with a stochastic approach for equivalence ratio fluctuations to account for the effect of fuel-air unmixedness. This split allows for computationally fast variations of the gas inlet condition and the consideration of different shares of pilot gas. The generation of emissions is split into a share of prompt formation at the flame front and a slower formation mechanism, occurring within the combustion products in the post flame region. The influence of unmixedness of the fuel-air mixture on both effects is taken into consideration by means of probability density functions (PDFs) of the equivalence ratio. These are modeled on the basis of sampled values from Large Eddy Simulations at the flame front and adapted for different shares of pilot gas. It is shown that with a superposition of Gaussian PDFs the equivalence ratio distribution at the flame front resulting from the main gas supply and the pilot share can be well approximated. Measurement data from experiments in atmospheric conditions as well as emission measurements from high pressure tests are used to evaluate the model. Good agreement is found for atmospheric data, allowing for explanations on the effect of pilot fuel ratio on emissions. For elevated pressure, only qualitative trends could be reproduced. Hypotheses to explain this deviation are made that motivate further research.} V03AT04A035 https://doi.org/10.1115/GT2021-59071 Turbo Expo: Power for Land, Sea, and Air 10.1115/GT2021-59071 M.Reumschüssel J.von Saldern T.Kaiser T.Reichel J.-P.Beuth B.Ćosić F.Genin K.Oberleithner C. O.Paschereit article Klukas.2020 International Journal of Hydrogen Energy 2020 10 10 45 56 32547--32561 A joint experimental and numerical investigation of turbulent flame anchoring at externally heated walls is presented. The phenomenon has primarily been studied for laminar flames and micro-combustion while this study focuses on large-scale applications and elevated Reynolds number flows. Therefore, a novel burner design is developed and examined for a diverse set of operating conditions. Hydroxyl radical chemiluminescence measurements are employed to validate the numerical method. The numerical investigation evaluates the performance of various hydrogen/air kinetics, Reynolds-averaged turbulence models and the eddy dissipation concept (EDC) as a turbulence-chemistry interaction model. Simulation results show minor differences between detailed chemical mechanisms but pronounced deviations for a reduced kinetic. The baseline k-ω turbulence model is assessed to most accurately predict flame front position and shape. Universal applicability of EDC modeling constants is contradicted. Conclusively, the flame anchoring concept is considered a promising approach for pilot flames in continuous combustion devices. Eddy dissipation concept;Hydrogen/air chemical kinetics;Steady flame anchoring;Wall heat transfer 03603199 10.1016/j.ijhydene.2020.08.201 S.Klukas M.Giglmaier N.A.Adams M.Sieber S.Schimek C. O.Paschereit article Bluemner2020cnf} Combustion and Flame 2020 6 216 300-315 In this work, the effect of different injector geometries and different outlet restrictions on the operating modes of a hydrogen-air Rotating Detonation Combustor (RDC) is investigated. The different operating modes are identified based on pressure measurements in the combustor annulus and the reactant supply, combined with high-speed video from the aft end of the combustor. The pressure frequency spectra are analyzed to determine the global operating mode in terms of number, direction, and speed of waves. The results explore the ability of the RDC to establish rotating, counter-rotating, and longitudinal waves, as well as their superpositions. A good agreement between longitudinal modes and the acoustic resonance frequencies of the RDC annulus was found. Overall, operation was found to be highly injector and outlet restriction dependent. Adding an outlet restriction helped to suppress counter-rotating waves, which is a prerequisite to stabilize single detonation waves. However, it was also shown to prompt high frequency pulsed operation. Apart from the total reactant supply pressure, the relative strength of the injectors was identified as a key factor for stable RDC operation. Pressure feedback into the reactant supply was observed to be dependent on the reactant supply pressure and the RDC operating mode. The study further revealed the presence of transverse resonance modes in the fuel plenum, however these oscillations were weak relative to the injector pressures and do not appear to influence the combustion. https://doi.org/10.1016/j.combustflame.2020.03.011 0010-2180 10.1016/j.combustflame.2020.03.011 R.Blümner M.Bohon C. O.Paschereit E.Gutmark article Wieser_2020 energies 2020 1 9 13 18 The flow field topology of passenger cars considerably changes under side wind conditions. This changes the surface pressure, aerodynamic force, and drag and performance of a vehicle. In this study, the flow field of a generic passenger vehicle is investigated based on three different side wind angles. The study aimed to identify vortical structures causing changes in the rear pressure distribution. The notchback section of the DrivAer model is evaluated on a scale of 1:4. The wind tunnel tests are conducted in a closed section with a splitter plate at a Reynolds number of 3 million. The side wind angles are 0° , 5°, and 10°. The three-dimensional and time-averaged flow field downstream direction of the model is captured by a stereoscopic particle image velocimetry system performed at several measurement planes. These flow field data are complemented by surface flow visualizations performed on the entire model. The combined approaches provide a comprehensive insight into the flow field at the frontal and side wind inflows. The flow without side wind is almost symmetrical. Longitudinal vortices are evident along the downstream direction of the A-pillar, the C-pillars, the middle part of the rear window, and the base surface. In addition, there is a ring vortex downstream of the vehicle base. The side wind completely changes the flow field. The asymmetric topology is dominated by the windward C-pillar vortex, the leeward A-pillar vortex, and other base vortices. Based on the location of the vortices and the pressure distributions measured in earlier studies, it can be concluded that the vortices identified in the wake are responsible for the local minima of pressure, increasing the vehicle drag. DrivAer; aerodynamics; wind tunnel; vehicle; flow visualization; PIV; wake structures; side wind; crosswind https://www.mdpi.com/1996-1073/13/2/320/htm doi.org/10.3390/en13020320 D.Wieser C. N.Nayeri C. O.Paschereit article Saverin2020 Journal of Physics: Conference Series 2020 1618 052070 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. https://doi.org/10.1088/1742-6596/1618/5/052070 10.1088/1742-6596/1618/5/052070 J.Saverin D.Marten N.Nayeri C. O.Paschereit article Alber2020 Wind Energy Science 2020 5 4 1645--1662 https://wes.copernicus.org/articles/5/1645/2020/ 10.5194/wes-5-1645-2020 J.Alber R.Soto-Valle M.Manolesos S.Bartholomay C. N.Nayeri M.Schönlau C.Menzel C. O.Paschereit J.Twele J.Fortmann article Asli2020 Journal of Engineering for Gas Turbines Power 2020 24 Any outlet restriction downstream of Pressure Gain Combustion (PGC), such as turbine blades, affects its flow field and may cause additional thermodynamic losses. The unsteadiness in the form of pressure, temperature and velocity vector fluctuations has a negative impact on the operation of conventional turbines. Additionally, experimental measurements and data acquisition present researchers with challenges that have to do mostly with the high temperature exhaust of PGC and the high frequency of its operation. Nevertheless, numerical simulations can provide important insights into PGC exhaust flow and its interaction with turbine blades. In this paper, a Rotating Detonation Combustor (RDC) and a row of nozzle guide vanes have been modeled based on the data from literature and an available experimental setup. URANS simulations were done for five guide vane configurations with different geometrical parameters to investigate the effect of solidity and blade type representing different outlet restrictions on the RDC exhaust flow. The results analyzed the connection between total pressure loss and the vanes solidity and thickness to chord ratio. It is observed that more than 57 % of the upstream velocity angle fluctuation amplitude was damped by the vanes. Furthermore, the area reduction was found to be the significant driving factor for damping the velocity angle fluctuations, whether in the form of solidity or thickness on chord ratio increment. This RDC exhaust flow investigation is an important primary step from a turbomachinery standpoint, which provided details of blade behavior in such an unsteady flow field. GTP-20-1512 Combustion chambers, explosions, guide vanes, exhaust systems, flow (Dynamics), pressure, blades, chords (Trusses), fluctuations (Physics), turbine blades, combustion, computer simulation, damping, data acquisition, engineering simulation, high temperature, nozzle guide vanes, simulation, temperature, turbines, turbomachinery, unsteady flow https://elib.dlr.de/139560/1/Manuskript.pdf https://doi.org/10.1115/1.4049188 M.Asli P.Stathopoulos C. O.Paschereit article Bach2019symp} Proceedings of the Combustion Institute 2020 10.1016/j.proci.2020.07.071 E.Bach C. O.Paschereit P.Stathopoulos M.Bohon article yuecel2019symp} Proceedings of the Combustion Institute 2020 10.1016/j.proci.2020.07.108 F.Yücel F.Habicht M.Bohon C. O.Paschereit article Perez-Becker2020 Wind Energy Science, vol. 5, pp. 721–743,(2020) 2020 5 5 721-743 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. https://doi.org/10.5194/wes-5-721-2020 10.5194/wes-5-721-2020 S.Perez-Becker F.Papi J.Saverin D.Marten A.Biancini C. O.Paschereit article Noack_29062020 Wind Energy Science 2020 5 2 819–838 Once stall has set in, lift collapses, drag increases and then both of these forces will fluctuate strongly. The result is higher fatigue loads and lower energy yield. In dynamic stall, separation first develops from the trailing edge up the leading edge. Eventually the shear layer rolls up, and then a coherent vortex forms and then sheds downstream with its low-pressure core causing a lift overshoot and moment drop. When 50+ experimental cycles of lift or pressure values are averaged, this process appears clear and coherent in flow visualizations. Unfortunately, stall is not one clean process but a broad collection of processes. This means that the analysis of separated flows should be able to detect outliers and analyze cycle-to-cycle variations. Modern data science and machine learning can be used to treat separated flows. In this study, a clustering method based on dynamic time warping is used to find different shedding behaviors. This method captures the fact that secondary and tertiary vorticity vary strongly, and in static stall with surging flow the flow can occasionally reattach. A convolutional neural network was used to extract dynamic stall vorticity convection speeds and phases from pressure data. Finally, bootstrapping was used to provide best practices regarding the number of experimental repetitions required to ensure experimental convergence. https://wes.copernicus.org/articles/5/819/2020/ https://doi.org/10.5194/wes-5-819-2020 M.Lennie J.Steenbuck B. R.Noack C. O.Paschereit article Balduzzi2020 ASME Digital Collection 2020 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. https://doi.org/10.1115/1.4048908 F.Balduzzi D.Holst P. F.Melani F.Wegner C. N.Nayeri G.Ferrara C. O.Paschereit A.Bianchini article Soto-Valle_2020 Wind Energy Science Discussions 2020 1-28 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 Föttinger Institut of the Technische Unversität 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. https://wes.copernicus.org/preprints/wes-2020-35/ 10.5194/wes-2020-35 R.Soto-Valle S.Bartholomay J.Alber M.Manolesos C. N.Nayeri C. O.Paschereit article Bohon2019shock} Shock Waves 2020 doi.org/10.1007/s00193-020-00975-8 M.Bohon A.Orchini R.Blümner C. O.Paschereit E.Gutmark article Müller-Vahl2020 AIAA Journal 2020 58 12 5134-5145 https://arc.aiaa.org/doi/pdf/10.2514/1.J059153 10.2514/1.j059153 H. F.Müller-Vahl C.Strangfeld C. N.Nayeri C. O.Paschereit D.Greenblatt article RezayHaghdoost2020a AIAA Journal 2020 58 8 3527--3543 https://arc.aiaa.org/doi/abs/10.2514/1.J058540 https://arc.aiaa.org/doi/10.2514/1.J058540 0001-1452 10.2514/1.J058540 M.Rezay Haghdoost D.Edgington-Mitchell C. O.Paschereit K.Oberleithner article Lückoff2020 Journal of Engineering for Gas Turbines and Power 2020 142 11 https://doi.org/10.1115/1.4048603 https://asmedigitalcollection.asme.org/gasturbinespower/article/doi/10.1115/1.4048603/1087526/Impact-of-the-Precessing-Vortex-Core-on-NOx {{}ASME{}} International 0742-4795 10.1115/1.4048603 F.Lückoff M.Sieber C. O.Paschereit K.Oberleithner article Asli_2020 22nd Australasian Fluid Mechanics Conference AFMC2020 Brisbane, Australia, 7 - 10 December 2020 2020 High level of unsteadiness existing in a high-temperature Rotating Detonation Combustor exhaust flow is extremely deteriorative for conventional turbomachinery that spoils the efficiency gained by constant volume combustion. In the present paper, it is tried to study the presence of a simple row of turbine guide vane downstream of an RDC. Unsteady numerical investigation is done on an experimental RDC model simulating three different operating modes all of which provide a single rotating detonation wave. Fluctuation frequency and amplitude are tracked to investigate the flow behavior in detail and the results are compared with the experimental measurements. Furthermore, total pressure loss is measured along the vanes. It is concluded that increasing RDC mass flow rate would lead to increase fluctuation frequency that also causes higher total pressure loss through the blade row. Additionally, three different flow regimes were observed for the different operating modes, which should be considered by turbine designers. Turbine guide vane; unsteady flow; rotating detonation; aerodynamic performance. https://espace.library.uq.edu.au/data/UQ_9e7ac3e/AFMC2020_Revised_paper_8.pdf?dsi_version=0e6eb909f71efa6567e9e9b41b4939c9&Expires=1614596146&Key-Pair-Id=APKAJKNBJ4MJBJNC6NLQ&Signature=IuB8BRStseU0E-bD3DHcCSeLUzM7V1a4OHeEVpahIDkjCtNIR43ynqKesm15BAQgK5jxRf https://doi.org/10.14264/9e7ac3e M.Asli P.Stathopoulos C. O.Paschereit article Yücel_2020 Journal of Engineering of gas turbines and power 2020 143 1 8 Shockless explosion combustor (SEC) is a promising concept for implementing pressure gain combustion into a conventional gas turbine cycle. This concept aims for a quasi-homogeneous auto-ignition that induces a moderate rise in pressure. Since the ignition is not triggered by an external source but driven primarily by chemical kinetics, the homogeneity of the auto-ignition is very sensitive to local perturbations in equivalence ratio, temperature, and pressure that produce undesired local premature ignition. Therefore, the precise injection of a well-defined fuel profile into a convecting air flow is crucial to ensure a quasi-homogeneous ignition of the entire mixture. The objective of this work is to demonstrate that the injected fuel profile is preserved throughout the entire measurement section. For this, two different control trajectories are investigated. Optical measurement techniques are used to illustrate the effect of turbulent transport and dispersion caused by boundary layer effects on the fuel concentration profile. Results from line-of-sight measurements by tunable diode laser absorption spectroscopy indicate that the transport of the fuel-air mixture is dominated by turbulent diffusion. However, comparisons to numerical calculations reveal the effect of dispersion toward the bounds of the fuel concentration profile. The spatially resolved distributions of the fuel concentration inside the combustor gained from acetone planar laser induced fluorescence (PLIF) replicates a typical velocity distribution of turbulent pipe flow in radial direction visualizing boundary layer effects. Comparing both methods provides deep insights into the transport processes that have an impact on the operation of the SEC. GTP-20-1504 Combustion chambers, fuels, lasers, air flow, cycles, explosions, fluorescence https://asmedigitalcollection.asme.org/gasturbinespower/article/143/1/011008/1091867/Investigation-of-the-Fuel-Distribution-in-a https://doi.org/10.1115/1.4049220 F.Yücel F.Habicht A.Jaeschke F.Lückoff C. O.Paschereit K.Oberleithner article Noack20200701 ERCIM News 2020 122 30-31 Reduced-order modelling and system identification can help us figure out the elementary degrees of freedom and theunderlying mechanisms from the high-dimensional and nonlinear dynamics of fluid flow. Machine learning has broughtnew opportunities to these two processes and is revolutionising traditional methods. We show a framework to obtain asparse human-interpretable model from complex high-dimensional data using machine learning and first principles. https://ercim-news.ercim.eu/images/stories/EN122/EN122-web.pdf 0926-4981 N.Deng L. R.Pastur B. R..Noack article Noack02102020 Journal of Fluid Mechanics 2020 884 A37 1-39 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. bifurcation, low-dimensional models, wakes https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/loworder-model-for-successive-bifurcations-of-the-fluidic-pinball/31E74B80FB2571D10D5166039B991BB3# 0022-1120 https://dx.doi.org/10.1017/jfm.2019.959 N.Deng B. R.Noack M.Morzyński L. R.Pastur article Biedermann_2020 ASME Journal of Engineering for Gas Turbines and Power 2020 142 11 13 A novel modeling strategy is proposed which allows high-accuracy predictions of aerodynamic and aeroacoustic target values for a low-pressure axial fan, equipped with serrated leading edges. Inspired by machine learning processes, the sampling of the experimental space is realized by use of a Latin hypercube design plus a factorial design, providing highly diverse information on the analyzed system. The effects of four influencing parameters (IP) are tested, characterizing the inflow conditions as well as the serration geometry. A total of 65 target values in the time and frequency domains are defined and can be approximated with high accuracy by individual artificial neural networks. Furthermore, the validation of the model against fully independent test points within the experimental space yields a remarkable fit, even for the spectral distribution in 1/3-octave bands, proving the ability of the model to generalize. A metaheuristic multi-objective optimization approach provides two-dimensional Pareto optimal solutions for selected pairs of target values. This is particularly important for reconciling opposing trends, such as the noise reduction capability and aerodynamic performance. The chosen optimization strategy also allows for a customized design of serrated leading edges, tailored to the specific operating conditions of the axial fan. GTP-20-1406 Acoustics, Artificial neural networks, Blades, design, fans, flow (dynamics), modeling, noise control, optimization, Pareto optimization, pressure, turbulence, noise (sound), rotors, signals, wavelength https://asmedigitalcollection.asme.org/gasturbinespower/article/142/11/111009/1087529/Multi-Objective-Modeling-of-Leading-Edge https://doi.org/10.1115/1.4048599 T. M.Biedermann M.Reich C. O.Paschereit article Bach2019cnf} Combustion and Flame 2020 217 21-36 This study explores the effect of differing inlet and outlet boundary conditions on the operation and performance of a rotating detonation combustor (RDC) over an annulus mass flux range of 50 to 210 and equivalence ratios of 0.7, 1.0, and 1.3. The RDC is equipped with either a uniform outlet restriction or with a set of nozzle guide vanes to simulate turbine integration. Stagnation pressure data from Kiel probes placed in the high-enthalpy exhaust flow are presented for the operational envelope. The RDC’s operation is categorized into different modes distinguished by the number of co- and counter-rotating combustion waves in the annulus. With increasing mass flux, a typical progression proceeding from a pair of counter-rotating waves, to a single detonation wave, and then further to multiple co-rotating waves is observed with wave speeds reaching up to 84% of the CJ velocity. It is shown that a choking condition at the outlet throat correlates with the transition from two counter-rotating waves to a single wave detonation regime. The channel Mach number is then calculated from measured pressure ratios and is shown to agree with area ratio-based estimates. The pressure gain of the RDC is expressed as the stagnation pressure change from the air plenum to the outlet throat, and it is shown that the specific operating mode of the device – in conjunction with the chosen injector and outlet area ratios – can significantly decrease the pressure gain performance in some cases, while not significantly affecting it in others. While no positive pressure gain was achieved in the experiments, the presented experimental data compare well with numerical results of similar boundary conditions and underline the importance of minimizing injector pressure loss while applying outlet restrictions to the combustor. The data also suggest that specific geometric combinations may lead to adverse modes such as longitudinally pulsing combustion, resulting in a reduction in the measured pressure gain relative to numerical results. This observation occurs more often for geometric combinations which are the most promising for exhibiting positive pressure gain, and suppressing these modes will be an important topic to achieving this goal. It is further shown that transition regions exist between modes of one and multiple co-rotating waves, and that wave multiplication may be necessary to unlock further increases in the pressure gain. https://doi.org/10.1016/j.combustflame.2020.03.017 0010-2180 10.1016/j.combustflame.2020.03.017 E.Bach P.Stathopoulos C. O.Paschereit M.Bohon article marten2020predicting AIAA Journal 2020 58 11 4672-4685 https://arc.aiaa.org/doi/10.2514/1.J058308 American Institute of Aeronautics and Astronautics 0001-1452 10.2514/1.J058308 D.Marten C. O.Paschereit X.Huang M.Meinke W.Schröder J.Müller K.Oberleithner article Müller2020 Journal of Fluid Mechanics 2020 888 A3 https://www.cambridge.org/core/product/identifier/S0022112019010632/type/journal{\_}article Cambridge University Press 0022-1120 10.1017/jfm.2019.1063 J.Müller F.Lückoff P.Paredes V.Theofilis K.Oberleithner article paredes-cisneros_simulation_2020 Physica Medica 2020 70 109--117 https://linkinghub.elsevier.com/retrieve/pii/S1120179720300144 11201797 10.1016/j.ejmp.2020.01.012 I.Paredes-Cisneros C.Karger P.Caprile D.Nolte I.Espinoza A.Gago-Arias article Vanierschot2020 Journal of Fluid Mechanics 2020 883 A31 https://www.cambridge.org/core/product/identifier/S0022112019008723/type/journal{\_}article Cambridge University Press (CUP) 0022-1120 10.1017/jfm.2019.872 M.Vanierschot J.Müller M.Sieber M.Percin B.van Oudheusden K.Oberleithner article Bluemner2019symp} Proceedings of the Combustion Institute 2020 10.1016/j.proci.2020.07.063 R.Blümner E.Gutmark C. O.Paschereit M.Bohon article Soto-Valle2020 Journal of Physics: Conference Series 2020 1618 032045 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.� https://doi.org/10.1088/1742-6596/1618/3/032045 10.1088/1742-6596/1618/3/032045 R.Soto-Valle J.Alber M.Manolesos C. N.Nayeri C. O.Paschereit conference Noack_2020 2020 1 6 active flow control, Coanda blowing, piezo actuator https://elib.dlr.de/127971/ AIAA Orlando, Fl. USA AIAA SciTech Forum 6-1-2020 Y.El-Sayed N.Gomes de Paula B.Genest R.Semaan J.Radespiel R.Petersen C.Behr P.Wierach B. R.Noack inproceedings rezay2020evaluation 2020 926 https://arc.aiaa.org/doi/10.2514/6.2020-0926 American Institute of Aeronautics and Astronautics

Reston, Virginia

AIAA Scitech 2020 Forum 978-1-62410-595-1 10.2514/6.2020-0926 M.Rezay Haghdoost B.Thethy M.Nadolski R.Klein D.Honnery D.Edgington-Mitchell B.Seo C. O.Paschereit K.Oberleithner inproceedings Bluemner2020scitech} 2020

Orlando, FL

AIAA Paper 2020-2287 10.2514/6.2020-2287 R.Blümner C. O.Paschereit E.Gutmark M.Bohon inproceedings Bach2020scitech 2020

Orlando, FL

AIAA Paper 2020-0199 10.2514/6.2020-0199 E.Bach C. O.Paschereit P.Stathopoulos M.Bohon inproceedings thethy2020redistribution 2020 925 https://arc.aiaa.org/doi/10.2514/6.2020-0925 American Institute of Aeronautics and Astronautics

Reston, Virginia

AIAA Scitech 2020 Forum 978-1-62410-595-1 10.2514/6.2020-0925 B.Thethy M.Rezay Haghdoost C. O.Paschereit D.Honnery D.Edgington-Mitchell KilianOberleithner article Asli2019 2019 11 28 10 Detonative Pressure Gain Combustion has the potential to increase the propulsion efficiency of aero-engines and the thermal efficiency of stationary gas turbines. Important advances were made in this field, especially in the case of Rotating Detonation Combustion (RDC). Although experimental and numerical studies reported in the literature have significantly increased in number, the major open problem is a lack of efficient turbomachinery to transform the fluctuating potential energy from an RDC into power output. For this problem to be properly addressed, time resolved data at the outlet of an RDC needs to be collected. As a first step, numerical data can be used to generate a geometry for the turbine, which must be validated experimentally. To determine the performance of a turbine vane row, total pressure losses need to be measured. There are several challenges in measuring the total pressure between the outlet of an RDC and the inlet of a turbine vane row. The high temperature values, the distance of the pressure transducer from the outlet of the combustor lead to a lower time resolution of the pressure signal. The confined space is also an issue, allowing for very few options in measuring the total pressure. Another major problem is the shock wave that may form as a detached shock wave with respect to the body of the pressure probe at certain moments in the flow cycle, which leads to measuring a different value rather than the actual value of the flow field. To address these issues, the current study presents a numerical investigation of a guide vane row that was experimentally tested at the outlet of an RDC working on hydrogen and air under stoichiometric conditions. One of the vane rows was 3D printed with a geometry allowing the measurement of total pressure. Static pressure at the outlet of the RDC was also measured. It was observed that the measured pressures are average values in time. Based on these averages, the total inlet pressure and velocity variations in time were reconstructed in an exponential trend, according to the ones reported in the literature and the aforementioned experiments. These variations were set as inlet conditions for transient numerical simulations. Results show that the total pressure amplitude decreases significantly when the flow passes the annulus and the vanes as well. By looking in to the flow field detail, the presence of shock wave in front of the blade is investigated. Additionally, it is calculated that the average total pressure decreases 7.9 % by the vane row. https://doi.org/10.1115/GT2019-91263 English 10.1115/GT2019-91263 M.Asli C.Cuciumita P.Stathopoulos C. O.Paschereit article Jentzsch_2019 ARC, AIAA 2019 1 6 https://arc.aiaa.org/doi/pdf/10.2514/6.2019-2164 10.2514/6.2019-2164 M.Jentzsch H. J.Schmidt R.Woszidlo C. N.Nayeri C. O.Paschereit article Tschepe2019_1 Springer 2019 16 The present study assesses the applicability of towing tank experiments using a moving model for the investigation of the aerodynamics of long land-borne heavy vehicles such as buses, trucks, and trains. Based on experiments with a 1:22 scaled model of a high-speed train, the influence of various conditions relevant for the transferability of the results obtained in water to air is analysed exemplarily. These conditions include surface waves, cavitation and submergence depth. The experiments were carried out in the shallow water towing tank of the Technische Universität Berlin. It is shown that outside a critical Froude number range of about 0.2 < Fr < 1.2 the impact of the surface waves can be neglected and no cavitation appears in the velocity range investigated. Furthermore, a correction method is proposed taking into account the bias through surface waves at small submergence and thus allowing for a wider Froude number range. The data obtained in the towing tank are found to be in excellent agreement to other investigation methods. https://link.springer.com/article/10.1007/s00348-019-2748-8 English 0723-4864 10.1007/s00348-019-2748-8 J.Tschepe C. N.Nayeri C. O.Paschereit article Marten2019 ASME 2019 141 4 13 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. GTP-18-1489 Blades, Rotors, Simulation, Turbines, Vertical axis wind turbines, Modal analysis, Flow (Dynamics), Vortices https://asmedigitalcollection.asme.org/gasturbinespower/article/141/4/041014/367187/Benchmark-of-a-Novel-Aero-Elastic-Simulation-Code English doi.org/10.1115/1.4041519 D.Marten M.Lenni G.Pechlivanoglu C. O.Paschereit A.Bianchini A.Ferrara L.Ferrari article Tanneberger2019 International Journal of Hydrogen Energy 2019 Oxy-fuel combustion, Hydrogen, Steam dilution, Combustion efficiency, Large scale energy storage http://www.sciencedirect.com/science/article/pii/S0360319919318865 0360-3199 https://doi.org/10.1016/j.ijhydene.2019.05.055 T.Tanneberger S.Schimek C. O.Paschereit P.Stathopoulos article Blümner_2019 International Journal of Hydrogen Energy 2019 44 7628 - 7641 This work describes an experimental study on the transition dynamics in a hydrogen-air RDC as the operating mode transitions from two steadily propagating, equally-fast counter-rotating waves to a single wave depending on the operating condition. The operating mode for a range of equivalence ratios and mass flow rates is investigated based on time-resolved measurements of the pressure in the combustor annulus at multiple azimuthal locations, as well as based on simultaneous measurements of the natural flame luminosity from the aft end of the RDC. Overall reactant mass flow and equivalence ratio, coupled with the plenum pressures, were confirmed as the driving parameters for wave mode transition. Further experimentation is necessary to decouple these effects, however the results illustrate complex transition dynamics, yielding an acceleration of the primary wave and the simultaneous deceleration of the secondary wave(s). At the same time the secondary wave number is observed to increase up to a triplet of counter-rotating waves. A non-dimensional wave dominance parameter is proposed, which links the relative wave speeds of the waves to thermodynamic properties of the combustor. It indicates regimes of constant wave mode that are independent of changing operating conditions and that extend far into the operating map for the given RDC geometry. The results further indicate a correlation between the operating mode with two counter-rotating waves and choked flames, as well as quasi-detonations observed in generic detonation experiments in the literature. https://doi.org/10.1016/j.ijhydene.2019.01.262 English 10.1016/j.ijhydene.2019.01.262 R.Blümner M.Bohon C. O.Paschereit E. J.Gutmark article Tanneberger_2019 Journal of Engineering for Gas Turbines and Power 2019 141 10 https://doi.org/10.1115/1.4044779 0742-4795 10.1115/1.4044779 T.Tanneberger S.Schimek C. O.Paschereit P.Stathopoulos article Holst2019 ASME 2019 141 4 12 Wind turbine industry has a special need for accurate post stall airfoil data. While literature often covers incidence ranges [−10 deg, +25 deg], smaller machines experience a range of up to 90 deg for horizontal axis and up to 360 deg for vertical axis wind turbines (VAWTs). The post stall data of airfoils is crucial to improve the prediction of the start-up behavior as well as the performance at low tip speed ratios. The present paper analyzes and discusses the performance of the symmetrical NACA 0021 airfoil at three Reynolds numbers (Re = 100 k, 140 k, and 180 k) through 180 deg incidence. The typical problem of blockage within a wind tunnel was avoided using an open test section. The experiments were conducted in terms of surface pressure distribution over the airfoil for a tripped and a baseline configuration. The pressure was used to gain lift, pressure drag, moment data. Further investigations with positive and negative pitching revealed a second hysteresis loop in the deep post stall region resulting in a difference of 0.2 in moment coefficient and 0.5 in lift. GTP-18-1576 Airfoils, Pressure, Reynolds number, Wind turbines, Experimental analysis, Wind tunnels, Drag (Fluid dynamics) https://doi.org/10.1115/1.4041651 English 10.1115/1.4041651 D.Holst B.Church G.,Pechlivanoglu E.Tüzüner J.Saverin C. N.Nayeri C. O.Paschereit article Blümner2019 Combustion and Flame 2019 209 99 - 116 In the context of thermoacoustic instabilities, knowledge about the generation and transport of equivalence ratio fluctuations is highly important to correctly model their impact on the flame transfer function. In this work, spatially resolved equivalence ratio perturbations in the mixing section of an acoustically forced, partially premixed swirl burner typical of modern gas turbine combustors are investigated. Tunable diode laser absorption spectroscopy using a wavelength-modulation approach is applied to assess the spatially inhomogeneous equivalence ratio field in the radial direction. Particle image velocimetry is applied to measure the axial velocity field. Based on these results, a tomographic reconstruction is utilized to deduce the local fuel distribution at two axial locations. Integrated, global equivalence ratio fluctuations are calculated and compared to simple line-of-sight measurements. The influence of the forcing frequency and amplitude is investigated and good agreement was found between the different measurement approaches. Frequency dependent equivalence ratio perturbation generation mechanisms driven by air velocity fluctuations in the swirler, as well as pressure fluctuations at the fuel injector, are observed. Two different mixing transfer functions modeling diffusion and dispersion are compared to the results and reveal substantial differences, indicating a significant impact of coherent fluctuations of the transport velocity on the mixing that are not accounted for by either of the models. Thermoacoustic instability, Equivalence ratio, Swirl burner, Laser absorption spectroscopy, Mixing https://doi.org/10.1016/j.combustflame.2019.07.007 English 10.1016/j.combustflame.2019.07.007 R.Blümner C. O.Paschereit K.Oberleithner article Bohon2019 Experimental Thermal and Fluid Science 2019 102 28 - 37 Various operating modes have been observed in the rotating detonation combustor (RDC) studied here, as well as by others. These modes can be generally categorized into two groups: one or more co-rotating waves and counter-rotating waves. The combustor is able to stabilize both types of operation, however the stabilization mechanism remains unclear. In order to better understand these cases, these operational modes are investigated with high-speed pressure transducers installed in the combustor annulus combined with simultaneous high-speed video imaging of the natural luminosity of the detonation wave from the aft end of the RDC. These results confirm the operation in both the steady single wave mode as well as the counter-rotating waves mode. The presence of this mode further demonstrates the complex dynamics inherent in the stabilization of the detonation wave. As each wave propagates, they initially begin to weaken followed by re-strengthening after collision which serves to stabilize the mode. Differences in the velocities of the waves was also observed to result in a beating phenomenon expressed as an amplitude modulation of the pressure traces. High-speed video imaging of the high-temperature emission from H2O in the RDC annulus was used in conjunction with the pressure traces for a range of flow rates and equivalence ratios. Processing of the images into the wave frame of reference allowed for the identification of the average luminosity profile, characterized by a steep increase in natural luminosity near the wave front, followed by a trailing tail extending approximately half the annulus perimeter. Rotating detonation high-speed video wave modes counter-rotating waves https://doi.org/10.1016/j.expthermflusci.2018.10.031 English 10.1016/j.expthermflusci.2018.10.031 M.Bohon R.Blümner C. O.Paschereit E. J.Gutmark article Zhang2019 Combustion Science and Technology 2019 191 1520 - 1540 This work assesses the effect of using different closure concepts for the spatially filtered mean reaction rate on the resolved spectral response of turbulent heat release in large eddy simulations (LESs). Two well-known combustion models, the turbulent flame speed closure (TFC) and the dynamically thickened flame (DTF) models have been applied to a premixed turbulent jet flame with otherwise identical numerical setups. Although the flame front is artificially thickened in the DTF model, it reproduces a thinner flame and, hence, stronger flame–turbulence interactions compared to the TFC model. As the time-averaged quantities from both methods are comparable, the DTF approach shows overall higher fluctuations of local and integral heat release rates in the spectral domain compared to the TFC model, particularly in the high-frequency range. A better agreement with measured sound pressure density is observed for TFC in the low-frequency range and for DTF in the high-frequency range. TFC simulations with different source formulations, that is, ω˙¯¯c∝c˜(1−c˜) and ω˙¯¯c∝∣∣∇c˜∣∣, showed comparable flame thicknesses and spectra of heat release, but the averaged flow quantities calculated with ω˙¯¯c∝∣∣∇c˜∣∣, however, deviate largely from measured data for the current setup. In the second step, the same formulations for the mean rate are applied to an excited plane-jet flame (two-dimensional (2D)) using equidistant grid cells and forced inflow conditions, thereby excluding the influence of varying grid resolution and broadband turbulent fluctuations. This setup is specifically tailored for a detailed analysis of flame response to flow unsteadiness and grid resolution. The formulation of the reaction rate according to the TFC approach again results in a considerably thicker flame compared to results obtained from the DTF model and direct numerical simulation, even on a sufficiently fine mesh. Therefore, the DTF formulation of the reaction rate shows overall stronger responses of heat release rates to forced fluctuations than the TFC formulation. Differences are smaller in the low-frequency range, indicating a stronger damping of heat release fluctuations with increasing frequency for the TFC formulation. Coarsening the grid leads to a much stronger damping of heat release fluctuations in the DTF formulation compared with the TFC formulation, so that the benefit of the DTF formulation decreases with decreasing grid resolution. This reflects the different sensitivity behavior of these models with respect to unsteady flows and grid resolutions, which is of great importance for computing thermoacoustic problems with LES, for example, combustion noise. Large eddy simulation, turbulent premixed flame, turbulent flame speed, thickened flame approach, OpenFOAM https://doi.org/10.1080/00102202.2018.1558218 English 10.1080/00102202.2018.1558218 F.Zhang T.Zirwes P.Habisreuther H.Bockhorn T.Dimosthenis H.Nawroth C. O.Paschereit article Tschepe'2019 Chalmers Research Publications 2019 102 417 - 434 In order to assess the accuracy of drag prediction methods for high-speed trains, experimental and numerical investigations were performed. Besides the drag coefficient, skin friction and pressure distributions on and near the model have been measured for a 1:22 model of the ICE/V. For the experiments, a moving model rig called DIWA (Drag measurement in water) was realised in a 120 m long towing tank to allow for a realistic simulation of the flow around the train, even in the underbelly region. Numerical investigations were performed using Partially-averaged Navier-Stokes (PANS) simulations based on the k-ω-SST turbulence model. Both experimental and numerical methods can be considered as a novelty in the field of train aerodynamics. The results are compared with data from full-scale tests. It is shown, that the moving model rig DIWA allows for the measurement of drag coefficients of trains with high accuracy. Furthermore, the data acquired using the PANS approach compares well with the experimental data. Towing tank, Train aerodynamics, Drag measurement, PANS, Moving model https://research.chalmers.se/en/publication/510116 1386-6184 10.1007/s10494-018-9962-y J.Tschepe D.Fischer C. N.Nayeri C. O.Paschereit S.Krajnovic article Pampaloni2019 Journal of Propulsion and Power 2019 35 994 - 1004 The prediction of thermo-acoustic instabilities is of paramount importance for gas-turbine combustion systems to meet the emission and efficiency targets. To predict the frequencies and amplitudes of pressure oscillations, and as a consequence, their impact on engine reliability, the nonlinear behavior of the system should be studied. An atmospheric lean-premixed combustor has been numerically investigated for validation purposes. A decoupled approach, separating the acoustic behavior and the nonlinear flame response, which is represented in this work by the flame describing function, has been used. As the first step, the flame describing function calculation from large-eddy simulations has been validated, including the effects of flame stretch and heat loss into the turbulence combustion model. Then, frequency-domain calculations using a three-dimensional Helmholtz solver have been carried out, and results have been validated against experimental measurements and a self-excited large-eddy simulation. https://apps.webofknowledge.com/full_record.do?product=WOS&search_mode=GeneralSearch&qid=10&SID=C4u2D5PtIHZKOxMnzhi&page=1&doc=2&cacheurlFromRightClick=no English 0748-4658 10.2514/1.B37490 D.Pampaloni A.Andreini B.Faccini C. O.Paschereit article Bohon_2019 Springer 2019 103 217 - 292 The cyclic propagation of detonation waves in the Rotating Detonation Combustor (RDC) make it an ideal candidate for using the cross-correlation technique. However, the potential for complicated operating modes combined with difficult diagnostic access introduces the possibility for ambiguous outcomes of the analysis. This work will first consider the specific details of the application of the technique to analyzing the features of RDC operation, including wave speed, direction, and operating mode. The accuracy and limitations of the technique will be quantified from a theoretical perspective. The second half of the work will focus on several example run conditions and operating modes in the RDC and will highlight differences in the analysis of variable combustion modes. From these cases studies, it is clear that a great deal of insight on the operation can be gleaned from analyzing the correlation. However, care must be taken in the experimental setup and analysis as a poorly designed approach can easily yield deceptive results. Finally, guidelines for preparing the experiment and conducting the analysis are provided to improve the quality of the results. Cross-correlation Rotating detonation combustion Operating modes Wave speed https://link.springer.com/article/10.1007/s10494-019-00017-z English 10.1007/s10494-019-00017-z M.Bohon R.Blümner C. O.Paschereit E. J.Gutmark article Lückoff2019 ASME 2019 141 J. Eng. Gas Turbines Power. Nov 2019, 141(11): 111008 (10 pages) 10 The precessing vortex core (PVC) is a helically shaped coherent flow structure that occurs in reacting and nonreacting swirling flows undergoing vortex breakdown. Inswirl-stabilized combustors, the PVC affects important phenomena, such as turbulent mixing and thermoacoustic oscillations. In this work, a closed-loop flow control system is developed, which allows for phase-opposition control of the PVC, to achieve appropriateconditions to systematically investigate the influence of the PVC on turbulent flames. The control consists of a zero-net-mass-flux actuator placed in the mixing section of the com-bustor, where the PVC is most receptive to periodic forcing. The flow control system is characterized from pressure measurements and particle image velocimetry (PIV) and the impact on flame dynamics is extracted from OH*-chemiluminescence measurements. The data reveal that the PVC amplitude is considerably suppressed by the phase-oppositioncontrol without changing the overall characteristics of flow and flame, which is crucial to study the exclusive effect of the PVC on combustion processes. Moreover, the control allows the PVC amplitude to be adjusted gradually to investigate the PVC impact on turbulent mixing and flame dynamics. It is revealed that the PVC-induced flow fluctuations mainly affect the large-scale mixing, while the small scale mixing remains unchanged.This is because the suppression of the PVC allows other modes to become more dominantand the overall turbulent kinetic energy (TKE) budget remains unchanged. The destabilization of other modes, such as the axisymmetric mode, may have some implications on thermoacoustic instability.[DOI: 10.1115/1.4044469]Keywords: active flow control, closed-loop control, precessing vortex core, spectral proper orthogonal decomposition (SPOD), swirl-stabilized combustion, particle image velocimetry (PIV) GTP-19-1377 active flow control, closed-loop control, precessing vortex core, spectral proper orthogonal decomposition (SPOD), swirl-stabilized combustion, particle image velocimetry (PIV) https://asmedigitalcollection.asme.org/gasturbinespower/article/141/11/111008/975561/Phase-Opposition-Control-of-the-Precessing-Vortex English Journal of Engineering for Gas Turbines and Power F.Lückoff M.Sieber C. O.Paschereit K.Oberleithner article Saurabh2019 Combustion Science and Technology 2019 1184 - 1200 Thermoacoustic instability in annular combustors involves feedback interaction between individual (acoustically compact) flames and – predominantly – azimuthal acoustic modes of the annular combustion chamber. During such an interaction, the flames experience acoustic pressure fluctuations in the combustor and transverse acoustic velocity fluctuations simultaneously. To investigate the dynamics of premixed swirl flames under the influence of transverse acoustics, experiments were performed on a single-burner atmospheric combustion rig with controlled simultaneous axial and transverse acoustic forcing, where the axial acoustics simulates the effect of acoustic pressure fluctuations in the combustor. In this paper, we present results on the descriptive analysis of spatially resolved flame surface fluctuations, acquired via OH-PLIF (OH* planar laser-induced florescence) diagnostics of the forced flame and establish the role of the interaction among coherent structures generated by axial and transverse velocity components in generating global flame response changes with respect to the phase difference between axial and transverse acoustic forcing as reported recently (Saurabh and Paschereit, Combustion Flame 182, 2017). Thermoacoustic Instability, Annular Combustors, Premixed Swirl Flames, Transverse Acoustics, Flame Response, OH PLIF https://doi.org/10.1080/00102202.2018.1516648 English 10.1080/00102202.2018.1516648 A.Saurabh C. O.Paschereit article Holst_2019 Journal of Engineering for Gas Turbines and Power 2019 141 10 The wind industry needs airfoil data for ranges of angle of attack (AoA) much wider than those of aviation applications, since large portions of the blades may operate in stalled conditions for a significant part of their lives. Vertical axis wind turbines (VARTs) are even more affected by this need, since data sets across the full incidence range of 180 deg are necessary for a correct performance prediction at different tip-speed ratios. However, the relevant technical literature lacks data in deep and poststall regions for nearly every airfoil. Within this context, the present study shows experimental and numerical results for the well-known NACA 0021 airfoil, which is often used for Darrieus VAWT design. Experimental data were obtained through dedicated wind tunnel measurements of a NACA 0021 airfoil with surface pressure taps, which provided further insight into the pressure coefficient distribution across a wide range of AoAs. The measurements were conducted at two different Reynolds numbers (Re = 140 k and Re = 180 k): each experiment was performed multiple times to ensure repeatability. Dynamic AoA changes were also investigated at multiple reduced frequencies. Moreover, dedicated unsteady numerical simulations were carried out on the same airfoil shape to reproduce both the static polars of the airfoil and some relevant dynamic AoA variation cycles tested in the experiments. The solved flow field was their exploited both to get further insight into the flow mechanisms highlighted by the wind tunnel tests and to provide correction factors to discard the influence of the experimental apparatus, making experiments representative of open-field behavior. The present study is then thought to provide the scientific community with high quality, low-Reynolds airfoil data, which may enable in the near future a more effective design of Darrieus VAWTs. GTP-18-1435 Airfoils, Computational fluid dynamics, Flow (Dynamics), Pressure, Reynolds number, Simulation, Wind tunnels, Blades, Cycles, Engineering simulation https://doi.org/10.1115/1.4041150 0742-4795 10.11115/1.4041150 D.Holst F.Balduzzi A.Bianchini B.Church F.Wegner G.Pechlivanoglou L.Ferrari G.Ferrara C. N.Nayeri C. O.Paschereit article Ostermann2019 Journal of Fluid Mechanics 2019 863 215 - 241 This experimental study investigates the fundamental flow field of a spatially oscillating jet emitted by a fluidic oscillator into an attached cross-flow. Dominant flow structures, such as the jet trajectory and dynamics of streamwise vortices, are discussed in detail with the aim of understanding the interaction between the spatially oscillating jet and the cross-flow. The oscillating jet is ejected perpendicular to the cross-flow. A moveable stereoscopic particle image velocimetry (PIV) system is employed for the plane-by-plane acquisition of the flow field. The three-dimensional, time-resolved flow field is obtained by phase averaging the PIV results based on a pressure signal from inside the fluidic oscillator. The influence of velocity ratio and Strouhal number is assessed. Compared to a common steady wall-normal jet, the spatially oscillating jet penetrates to a lesser extent into the cross-flow’s wall-normal direction in favour of a considerable spanwise penetration. The flow field is dominated by streamwise-oriented vortices, which are convected downstream at the speed of the cross-flow. The vortex dynamics exhibits a strong dependence on the Strouhal number. For small Strouhal numbers, the spatially oscillating jet acts similar to a vortex-generating jet with a time-dependent deflection angle. Accordingly, it forms time-dependent streamwise vortices. For higher Strouhal numbers, the cross-flow is not able to follow the motion of the jet, which results in a quasi-steady wake that forms downstream of the jet. The results suggest that the flow field approaches a quasi-steady behaviour when further increasing the Strouhal number. fluid oscillator ; jets ; flow field ; cross-flow ; fluidischer Oszillator https://depositonce.tu-berlin.de//handle/11303/9074 English 0022-1120 10.1017/jfm.2018.981 F.Ostermann R.Woszidlo C. N.Nayeri C. O.Paschereit inbook Ostermann2019 2019 1 6 https://arc.aiaa.org/doi/abs/10.2514/6.2019-0887 AIAA SciTech Forum 10.2514/6.2019-0887 F.Ostermann R.Woszidlo C. N.Nayeri C. O.Paschereit article Schmidt2018 Experiments in Fluids 2018 6 The time-resolved flow field in the wake of a rectangular bluff body in ground proximity is examined through wind tunnel experiments. In addition to an extensive assessment of the baseline wake dynamics, the study also investigates the impact of passive (i.e., base flaps) and active (i.e., fluidic oscillators) flow control on the wake dynamics. The velocity field downstream of the model is acquired with a stereoscopic high-speed particle image velocimetry system at several streamwise and crosswise sections. Coherent wake structures are determined by conditional averaging, spectral analysis, and spectral proper orthogonal decomposition. The baseline flow field is dominated by a wake bi-stability that is characterized by a random shift between two stable wake states. The bi-stability is governed by the model’s aspect ratio and occurs in the vertical direction, because the model height is 1.35 times larger than its width. Higher frequency modes with less energy content as determined in the appropriate literature are identified and visualized. A coupling between these modes and the bi-stability is discussed. Flow control has a significant impact on the wake dynamics. When passive flow control is applied, the bi-stability of the wake is still present for a flap angle of 20∘. The higher frequency modes are still detectable but weakened. The turbulence intensity is significantly reduced when the flow attaches to the base flaps and the bi-stability is inhibited. When active flow control is applied, the higher baseline frequencies are suppressed in addition to the absence of the bi-stability. Solely the dominant mode at a Strouhal number of about 0.08 remains present for all flow control configurations. This mode is attributed to an alternating shear layer oscillation. https://link.springer.com/article/10.1007%2Fs00348-018-2560-x 1432-1114 10.1007/s00348-018-2560-x H.-J.Schmidt R.Woszidlo C. N.Nayeri C. O.Paschereit article Stangfeld2018 Aeorspace Research Central, AIAA 2018 5 8 Experiments indicate that vortices trailing finite wings can be perturbed by periodic wing pitching, leading to rapid dissipation and bursting. To illustrate the perturbation mechanism, Betz vortex rollup relations are combined with the Theodorsen theory for unsteady lift response. A sinusoidal pitch motion on a rigid elliptic planform wing is computed in this study as one example. Pitching modifies the instantaneous lift due to the planform variations, via the reduced frequency, and the rollup relations are applied to low-frequency experimental conditions. The combined Betz–Theodorsen theory shows that relatively large spanwise perturbations of the vortex centers can be achieved and may accelerate the exponential growth associated with the Crow instability. In fact, 84.2 % of the displacement of the unsteady trailing vortices due to unsteady pitching is oriented in the direction of the Crow instability. Furthermore, the axial velocity in the vortex center, calculated based on the Batchelor method, varies on the order of the flight speed. This forms two types of stagnation points produced by approaching and retreating axial core velocities; in the former case, conservation of mass leads to observations of “bursting.” This observation can be explained adequately on the basis of quasi-steady considerations. https://arc.aiaa.org/doi/10.2514/1.C034646 0021-8669 (print) or 1533-3868 (online) https://doi.org/10.2514/1.C034646 C.Strangfeld C. N.Nayeri C. O.Paschereit S.Greenblatt article Saverin2018 Journal of Engineering Gas Turbine Power 2018 4 12 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. GTP-17-1608 http://gasturbinespower.asmedigitalcollection.asme.org/article.aspx?articleid=2678430 10.1115/1.4039935 J.Saverin D.Marten D.Holst G.Pechlivanoglou C. N.Nayeri C. O.Paschereit G.Persico article Klein2018 Wind Energy Science 2018 3 349 - 460 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. https://doi.org/10.5194/wes-3-439-2018 10.5194/wes-3-439-2018 A. C.Klein S.Bartholomay D.Marten T.Lutz G.Pechlivanoglou C. N.Nayeri C. O.Paschereit E.Krämer article Bartholomay_2018 Proceedings of he ASME Turbo Expo 2018 2018 9 Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy GT2018-76977, pp. V009T48A016 11 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. Oslo, Norway, June 11 - 15, 2018 http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleID=2701583 Bartholomay S., Marten D., Sánchez Martinez M., Alber J., Pechlivanoglou G., Nayeri C. N., Paschereit C. O., Klein A, Lutz Th. and Krämer E. ASME Turbo Expo 2018 ASME 978-0-7918-5118-0 10.1115/GT2018-76977 S.Bartholomay D.Marten M.Sánchez Martinez J.Alber G.Pechlivanoglou C. N.Nayeri C. O.Paschereit A. C.Klein L.Thorsten E.Krämer article Saverin_2018 Aerospace Research Central 2018 AIAA 2018-0254 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. 2018 Wind Energy Symposium Kissimmee, Florida https://arc.aiaa.org/doi/10.2514/6.2018-0254 10.2514/6.2018-0254 J.Saverin D.Marten C. N.Nayeri G.Pechlivanoglou C. O.Paschereit article Marten2018 Aerospace Research Central 2018 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. AIAA SciTech Forum 2018 Wind Energy Symposium, Kissimmee, Florida https://arc.aiaa.org/doi/10.2514/6.2018-1246 10.2514/6.2018-1246 D.Marten S.Bartholomay G.Pechlivanoglou C. N.Nayeri C. O.Paschereit A.Fischer Th.Lutz article Lennie2018 Journal of Engineering Gas Turbine Power 2018 15 During the commissioning and stand-still cycles of wind turbines, the rotor is often stopped or even locked leaving the rotor blades at a standstill. When the blades are at a stand still, angles of attack on the blades can be very high and it is therefore possible that they experience vortex induced vibrations. This experiment and analysis helps to explain the different regimes of flow at very high angles of attack, particularly on moderately twisted and tapered blades. A single blade was tested at two different flow velocities at a range of angles of attack with flow tuft visualisation and hotwire measurements of the wake. Hotwire wake measurements were able to show the gradual inception and ending of certain flow regimes. The power spectral densities of these measurements were normalized in terms of Strouhal number based on the projected chord to show that certain wake features have a relatively constant Strouhal number. The shedding frequency appears then to be relatively independent of chord taper and twist. Vortex generators were tested but were found to have little influence in this case. Gurney flaps were found to modify the wake geometry, stall onset angles and in some cases the shedding frequency. GTP-17-1616 http://gasturbinespower.asmedigitalcollection.asme.org/article.aspx?articleid=2677759 10.1115/1.4039818 M.Lennie A.Selahi-Moghaddam D.Holst G.Pechlivanoglou C. N.Nayeri C. O.Paschereit conference Perez-Becker_2020 2018 9 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. GT2018-76078, V009T48A008; 11 pages https://asmedigitalcollection.asme.org/GT/proceedings-abstract/GT2018/51180/V009T48A008/273154 ASME 978-0-7918-5118-0 10.1115/GT2018-76078 S.Perez-Becker J.Saverin D.Marten J.Alber G.Pechlivanoglou C. O.Paschereit inproceedings Holst2018a 2018 6 12 The wind industry needs airfoil data for ranges of Angle of Attack (AoA) much wider than those of aviation applications, since large portions of the blades may operate in stalled conditions for a significant part of their lives. Vertical axis wind turbines (VAWTs) are even more affected by this need, since data sets across the full incidence range of 180 degree are necessary for a correct performance prediction at different tip-speed ratios. However, the relevant technical literature lacks data in deep and post stall regions for nearly every airfoil. Within this context, the present study shows experimental and numerical results for the well-known NACA 0021 airfoil, which is often used for Darrieus VAWT design. Experimental data were obtained through dedicated wind tunnel measurements of a NACA 0021 airfoil with surface pressure taps, which provided further insight into the pressure coefficient distribution across a wide range of AoAs. The measurements were conducted at two different Reynolds umbers (Re=140k and Re=180k): each experiment was performed multiple times to ensure repeatability. Dynamic AoA changes were also investigated at multiple reduced frequencies. Moreover, dedicated unsteady numerical simulations were carried out on the same airfoil shape to reproduce both the static polars of the airfoil and some relevant dynamic AoA variation cycles tested in the experiments. The solved flow fieldwas then exploited both to get further insight into the flow mechanisms highlighted by the wind tunnel tests and to provide correction factors to discard the influence of the experimental apparatus, making experiments representative of open-field behaviour. The present study is then thought to provide the scientific community with high quality, low-Reynolds airfoil data, which may enable in the near future a more effective design of Darrieus VAWTs. GT2018-75426 https://www.asme.org/events/turbo-expo2018 ASME Proceedings of ASME Turbo Expo 2018 Turbomachinery Technical Conference and Exposition Proceedings of the ASME Turbo Expo 2018 ASME D.Holst F.Balduzzi A.Bianchini B.Church F.Wegner G.Pechlivanoglou L.Ferrari G.Ferrara C. N.Nayeri C. O.Paschereit inproceedings Holst2018b 2018 12 The wind industry needs reliable and accurate airfoil polars to properly predict wind turbine performance, especially during the initial design phase. Medium- and low-fidelity simulations directly depend on the accuracy of the airfoil data and even more so if e.g. dynamic effects are modeled. This becomes crucial if the blades of a turbine operate under stalled conditions for a significant part of the turbine’s lifetime. In addition, the design process of vertical axis wind turbines (VAWTs) needs data across the full range of angles of attack between 0 and 180 deg. Lift, drag and surface pressure distributions of a NACA 0021 airfoil equipped with surface pressure taps were investigated based on time-resolved pressure measurements. The present study discusses full range static polars and several dynamic sinusoidal pitching configurations covering two Reynolds numbers Re = 140k and 180 k, and different incidence ranges: near stall, post stall and deep stall. Various bi-stable flow phenomena are discussed based on high frequency measurements revealing large lift-fluctuations in the post and deep stall regime that exceed the maximum lift of the static polars and are not captured by averaged measurements. Detailed surface pressure distributions are discussed to provide further insight into the flow conditions and pressure development during dynamic motion. The experimental data provided within the present paper is dedicated to the scientific community for calibration and reference purposes, which in the future may lead to higher accuracy in performance predictions during the design process of wind turbines. GT2018-76514 https://www.asme.org/events/turbo-expo2018 ASME Proceedings of ASME Turbo Expo 2018 Turbomachinery Technical Conference and Exposition Proceedings of the ASME Turbo Expo 2018 ASME D.Holst B.Church F.Wegner G.Pechlivanoglou C. N.Nayeri C. O.Paschereit article Reichel_2017 2017 12 108 The focus of this study is the combustion of hydrogen in air as it relates to typical gas turbine engines. Hydrogen–air combustion occurs in the absence of any carbon-based emissions and the only combustion products are water vapor and oxides of nitrogen (NOx). However, due to the very low flammability limit of hydrogen, it can be burned at much lower equivalence ratios than typical hydrocarbon fuels, resulting in excellent low NOx potential. Lean premixed combustion of low reactivity fuels, such as natural gas, is nowadays state of the art in stationary gas turbines. In the long term, it is also a promising approach for aero engines. For lean premixed combustion, with increasing fuel reactivity lean blow out limits are extended but the disposition for flashback, an undesired event of upstream flame propagation, is increased. Therefore, combustor design strategies that are applied for conventional fuels have to be revisited in case of hydrogen, which represents the upper end of the scale of high reactivity fuels. The current thesis aims at developing a combustor design that is capable of safely operating on hydrogen–air mixtures up to stoichiometric conditions while meeting strict emission regulations. To this end, several measures affecting the flashback resistance of a hydrogen–air combustor are investigated. In addition to their effect on flashback resistance, all measures are evaluated with respect to their impact on fuel–air mixing which directly affects NOx emissions. Unlike most previous investigations on hydrogen–air combustion, the current investigations are conducted at partially premixed instead of perfectly premixed conditions. This poses a challenging task with respect to achieving flashback resistance as well as low \mathrm{NO_x} emissions with limited premixing space and time. Experimental investigation of non-reacting and reacting combustor flow fields of a partially premixed model combustor were conducted using particle image velocimetry in an atmospheric combustor tests rig. Results reveal a strong influence of geometric modifications and fuel momentum on the combustor flow field. Stability maps were recorded that allow for comparison of the operational range of different combustor geometries with respect to flashback and lean blow out. It was shown that already moderate flow rates of a central non-swirling air jet significantly extend the flashback limits, while the lean blow out limits remained unaffected. Moreover, recordings of planar laser-induced fluorescence of the hydroxyl radical (OH-PLIF) within the flame revealed that, the axial location of the upstream flame front, x_f, constitutes a telling estimator for flashback resistance. At the investigated conditions, x_f is shifted downstream with increasing equivalence ratio due to the added momentum of the fuel flow. Thereby, the local gain in axial velocity due to fuel momentum supersedes any parallel augmentation in the turbulent flame speed. This has been identified as a driving mechanism affecting the combustor stability limit.Performance and emissions data facilitate the conclusion that the desired flashback-safe operation at very low NOx emissions at ambient pressure and relevant combustor inlet temperatures is feasible. Der Fokus dieser Arbeit liegt auf der experimentellen Untersuchung von Maßnahmen zur Gewährleistung der sicheren und schadstoffarmen Verbrennung von Wasserstoff mit Luft in einer Gasturbine. Die Verbrennung von Wasserstoff mit Luft geschieht ohne den Ausstoß jeglicher Kohlenwasserstoffe, sodass sich das Abgas ausschließlich aus Wasserdampf und Stickoxiden zusammensetzt. Der Stickoxidanteil kann dabei auf ein Minimum begrenzt werden da Wasserstoff aufgrund seiner weiten Zündgrenzen extrem mager verbrannt werden kann. Mager vorgemischte Verbrennung, wie sie heutzutage bereits in stationären Gasturbinen zum Standard gehört, stellt mittelfristig auch einen vielversprechenden Ansatz für Fluggasturbinen dar. Der Einsatz hochreaktiver Brennstoffe, zum Beispiel wasserstoffreiche Synthesegase oder reiner Wasserstoff, erweitert zwar einerseits deutlich den mageren Betriebsbereich. Andererseits erhöht sich auch enorm das Risiko des Auftretens von Flammenrückschlag, welcher zu massiver Beschädigung von Bauteilen führen kann. Die konventionellen Konzepte der Brennerentwicklung müssen daher für hochreaktive System neu gedacht werden, insbesondere für die Verbrennung von reinem Wasserstoff, der das obere Ende der Skala hochreaktiver Gasturbinentreibstoffe darstellt. Im Rahmen dieser Doktorarbeit wird der Einfluss verschiedener Maßnahmen zur Vermeidung von Flammenrückschlag auf das nicht-reagierende und reagierende Strömungsfeld experimentell untersucht. Darüber hinaus werden die Auswirkungen dieser Änderungen des Strömungsfeldes auf die Flammenstabilisierung mit Hilfe moderner optischer Messtechnik gezeigt. Die daraus gewonnenen Erkenntnisse vermögen die Beobachtungen der gemessenen Stabilitätskarten zu erklären. Durch die Identifikation von Indikatoren für Flammenrückschlag lassen sich außerdem Voraussagen für die Stabilität jenseits des experimentell bestimmten Betriebsbereichs treffen. Im Rahmen der Untersuchungen stellte sich insbesondere das Störungsfreie Einbringen des hohen Brennstoffimpulses als kritische Maßnahme zur Wahrung von Flammenrückschlagsicherheit heraus. Weiterhin wurde gezeigt das verschiedene Maßnahmen zur Vermeidung von Flammenrückschlag interagieren und teilweise interferieren. Es konnte jedoch gezeigt werden dass die vorgeschlagene Kombination der Maßnahmen in der Brennergeometrie in der Lage ist Flammenrückschlag auf dem gesamten Betriebsbereich der Versuchsanlage zu verhindern und gleichzeitig ambitionierte Emissionsziele zu erfüllen. https://depositonce.tu-berlin.de//handle/11303/7254 http://dx.doi.org/10.14279/depositonce-6530 Technische Universität Berlin phdthesis English T. G.Reichel S.Terhaar C. O.Paschereit article Zanuy2017 Eisenbahntechnische Rundschau 2017 5 5 78 - 81 In diesem Artikel wird die Entwicklung einer Berechnungsformel für den aerodynamischen Widerstand von Containerzügen vorgestellt, in Abhängigkeit von Zuglänge, Abstand der auf dem Zug verladenen Container und Zuggeschwindigkeit. Hierzu wurden ein CFD-Modell (computational fluid dynamics model) erstellt und Windkanalversuche ausgewertet. Bei einem mit 100 km/h fahrenden Containerzug der Deutschen Bahn AG ist der Luftwiderstand für 44 % des Energieverbrauchs der Zugfahrt verantwortlich. Der Abstand zwischen den Containern spielt dabei eine große Rolle. Anders als bei Hochgeschwindigkeitszügen, die aerodynamisch optimiert sind, und bei Sattelschleppern im Straßen-Fernverkehr, bei denen der Energieverbrauch durch aerodynamische Formgebung reduziert werden konnte, fand dieses Thema im Güterverkehr auf der Schiene bisher wenig Beachtung. http://www.eurailpress.de/archiv/fachartikelarchiv/ergebnisliste/artikelansicht.html?tx_it24archiv_list%5Barticle%5D=13361&tx_it24archiv_list%5Baction%5D=show&tx_it24archiv_list%5Bcontroller%5D=Article&cHash=6a63329fb4be304879af99d684076628 ETR A. C.Zanuy C. N.Nayeri O. S.Pérez article Lennie2017 AIAA SciTech Forum 2017 1 https://arc.aiaa.org/doi/abs/10.2514/6.2017-2002 Aerospace Research Central 10.2514/6.2017-2002 M.Lennie J.Wendler D.Marten G.Pechlivanoglou C. O.Paschereit article Marten2017 Aerospace Research Central, AIAA SciTech Forum 2017 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. 35th Wind Energy Symposium 9 - 13 January 2017 Grapevine, Texas http://dx.doi.org/10.2514/MWES17 10.2514/6.2017-0452 D.Marten M.Lennie G.Pechlivanoglou C. O.Paschereit N. V.Dy I.Paraschivoiu F.Saeed inbook Menzel2017 2017 430 - 434 http://www.etz.de/files/10_02_menzel-holst-fischer.pdf Rahman J., Heinze R. VDE Verlag Forschung und Lehre in Virtuelle Instrumente in der Praxis 2017 978-3-800-4441-1 C.Menzel D.Holst J.Fischer C. N.Nayeri C. O.Paschereit inproceedings Alber2017 2017 8 17 10 This paper presents a strategy to model the aerodynamic Gurney flap effect on two-dimensional airfoils and subsequently on the rotor blade performance of horizontal axis wind turbines.The first part consists of the parametric investigation of 26 airfoil polar data-sets, derived from different, but comparable, wind tunnel experiments. They are evaluated and processed in terms of the lift and drag increase caused by Gurney flaps in comparison to each Baseline configuration. Consequently, a model is developed, transforming Baseline- into Gurney flap polar data for varying flap-heights. The results of the emerging Gurney Flap Polar Calculator are validated against the experimental lift and drag curves.In the second part, the blade design of the NREL 5 MW Reference Turbine is modified by implementing polar data-sets of varying Gurney flap-heights, which are imported into the rotor simulation software QBlade. Thereupon, blade optimization strategies are examined regarding the two main Gurney flap applications on rotor blades: the retrofit and the design solution. The optimized retrofit solution on existing blades indicates power performance improvements, albeit at the expense of increasing structural loads. The optimized design solution on to-be-constructed blades, on the other hand, suggests chord-length reductions, while keeping the performance characteristics on a similar or even enhanced level.It is concluded that aerodynamic improvements are achieved by relatively small Gurney flap-heights, which are applied at specific blade positions. Blades, Wind turbines, Design, Rotors, Airfoils, Drag (Fluid dynamics), Chords (Trusses), Computer software, Horizontal axis wind turbines, Optimization, Performance characterization, Simulation, Stress, Turbines, Wind tunnels https://doi.org/10.1115/GT2017-64475 ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition 978-0-7918-5096-1 J.Alber G.Pechlivanoglou C. O.Paschereit J.Twele G.Weinzierl inproceedings Holst2017 2017 6 30 9 12 Wind turbine industry has a special need for accurate post stall airfoil data. While literature often covers incidence ranges [−10deg,+25deg] smaller machines experience a range of up to 90 deg for horizontal axis and up to 360 deg for vertical axis wind turbines (VAWTs). The post stall data of airfoils is crucial to improve the prediction of the start-up behavior as well as the performance at low tip speed ratios. The present paper analyzes and discusses the performance of the symmetrical NACA 0021 airfoil at three Reynolds numbers (Re = 100k, 140k, and 180k) through 180 deg incidence. The typical problem of blockage within a wind tunnel was avoided using an open test section. The experiments were conducted in terms of surface pressure distribution over the airfoil for a tripped and a baseline configuration. The pressure was used to gain lift, pressure drag, moment data. Further investigations with positive and negative pitching revealed a second hysteresis loop in the deep post stall region resulting in a difference of 0.2 in moment coefficient and 0.5 in lift. http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2650571 ASME Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition ASME Charlotte, North Carolina, USA ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition 26 - 30 Juni 2017 English ISBN: 978-0-7918-5096-1 10.1115/GT2017-63643 D.Holst B.Church G.Pechlivanoglou E.Tüz Üner J.Saverin C. N.Nayeri C. O.Paschereit inproceedings Holst2017a 2017 6 9 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. http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2650574 ASME Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition ASME Charlotte, North Carolina, USA ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition 26 - 30 Juni 2017 English ISBN: 978-0-7918-5096-1 10.1115/GT2017-64004 J.Saverin D.Marten D.Holst G.Pechlivanloglou C. N.Nayeri C. O.Paschereit inproceedings Holst2017b 2017 6 9 17 During the commissioning and stand-still cycles of wind turbines, the rotor is often stopped or even locked leaving the rotor blades at a standstill. When the blades are at a stand still, angles of attack on the blades can be very high and it is therefore possible that they experience vortex induced vibrations. This experiment and analysis helps to explain the different regimes of flow at very high angles of attack, particularly on moderately twisted and tapered blades. A single blade was tested at two different flow velocities at a range of angles of attack with flow tuft visualisation and hotwire measurements of the wake. Hotwire wake measurements were able to show the gradual inception and ending of certain flow regimes. The power spectral densities of these measurements were normalized in terms of Strouhal number based on the projected chord to show that certain wake features have a relatively constant Strouhal number. The shedding frequency appears then to be relatively independent of chord taper and twist. Vortex generators were tested but were found to have little influence in this case. Gurney flaps were found to modify the wake geometry, stall onset angles and in some cases the shedding frequency. http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2650572 ASME Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition ASME Charlotte, North Carolina, USA ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition 26 - 30 Juni 2017 English 0.1115/GT2017-63653 M.Lennie A.Selahi-Moghaddam D.Holst G.Pechlivanoglou C. N.Nayeri C. O.Paschereit article Grewe2016 Meteorologische Zeitschrift 2016 10 139 1 - 15 Air traffic is important to our society and guarantees mobility especially for long distances. Air traffic is also contributing to climate warming via emissions of CO2 and various non-CO2 effects, such as contrail-cirrus or increase in ozone concentrations. Here we investigate the climate impact of a future aircraft design, a multi fuel blended wing body (MF-BWB), conceptually designed within the EU-project AHEAD. We re-calculate the parameters for the contrail formation criterion, since this aircraft has very different characteristics compared to conventional technologies and show that contrail formation potentially already occurs at lower altitudes than for conventional aircraft. The geometry of the contrails, however, is similar to conventional aircraft, as detailed LES simulations show. The global contrail-cirrus coverage and related radiative forcing is investigated with a climate model including a contrail-cirrus parameterisation and shows an increase in contrail-cirrus radiative forcing compared to conventional technologies, if the number of emitted particles is equal to conventional technologies. However, there are strong indications that the AHEAD engines would have a substantial reduction in the emission of soot particles and there are strong indications that this leads to a substantial reduction in the contrail-cirrus radiative forcing. An overall climate impact assessment with a climate-chemistry response model shows that the climate impact is likely to be reduced by 20 % to 25 % compared to a future aircraft with conventional technologies. We further tested the sensitivity of this result with respect to different future scenarios for the use of bio fuels, improvements of the fuel efficiency for conventional aircraft and the impact of the number of emitted soot particles on the radiative forcing. Only the latter has the potential to significantly impact our findings and needs further investigation. Our findings show that the development of new and climate compatible aircraft designs requires the inclusion of climate impact assessments already at an early stage, i.e. pre-design level. Online veröffentlicht: Oct 14, 2016 Manuskript akzeptiert: Jun 22, 2016 Manuskript-Revision erhalten: Jun 16, 2016 Manuskript-Revision angefordert: Jan 2, 2014 Manuskript erhalten: Nov 18, 2015 AHEAD project • Multi fuel blended wing body • contrails • climate impact • air traffic http://www.schweizerbart.de/papers/metz/detail/prepub/87038/Assessing_the_climate_impact_of_the_AHEAD_multi_fuel_blended_wing_body Schweizerbart Science Publishers

Stuttgart, Germany

online Oct 14, 2016 10.1127/metz/2016/0758 V.Grewe L.Bock U.Burkhardt K.Dahlmann K.Gierens L.Hüttenhofer S.Unterstrasser A. G.Rao A.Bhat F.Yin T. G.Reichel C. O.Paschereit Y.Leshayahou article Lennie2016 Journal of Physics 2016 10 Conference Series, 753 http://iopscience.iop.org/article/10.1088/1742-6596/753/8/082012/meta IOPscience 10.1088/1742-6596/753/8/082012 M.Lennie D.Marten G.Pechlivanoglou C. N.Nayeri C. O.Paschereit article Sieber_2016 Journal of Engineering for Gas Turbines and Power 2016 9 http://gasturbinespower.asmedigitalcollection.asme.org/article.aspx?articleid=2539421 10.1115/1.4034261 M.Sieber C. O.Paschereit K.Oberleithner article Sieber2016_ Physical Review Fluids 2016 9 1 http://dx.doi.org/10.1103/APS.DFD.2015.GFM.V0015 10.1103/PhysRevFluids.1.050509 M.Sieber F.Ostermann R.Woszidlo K.Oberleithner C. O.Paschereit article Rukes_2016 Journal of Engineering for Gas Turbines and Power 2016 9 139 http://gasturbinespower.asmedigitalcollection.asme.org/article.aspx?articleid=2541041 10.1115/gt2016-56588 L.Rukes M.Sieber C. O.Paschereit K.Oberleithner article Rukes2016_ Physics of Fluids 2016 9 28 http://scitation.aip.org/content/aip/journal/pof2/28/10/10.1063/1.4963274 L.Rukes M.Sieber C. O.Paschereit K.Oberleithner article Reichel2016 ASME Journal of Engineering for Gas Turbines and Power 2016 6 139 2 Approximate constant volume combustion (aCVC) is a promising way to achieve a step change in the efficiency of gas turbines. This work investigates a recently proposed approach to implement aCVC in a gas turbine combustion system: shockless explosion combustion (SEC). The new concept overcomes several disadvantages such as sharp pressure transitions, entropy generation due to shock waves, and exergy losses due to kinetic energy which are associated with other aCVC approaches such as pulsed detonation combustion. The combustion is controlled via the fuel/air mixture distribution which is adjusted such that the entire fuel/air volume undergoes a spatially quasi-homogeneous auto-ignition. Accordingly, no shock waves occur and the losses associated with a detonation wave are not present in the proposed system. Instead, a smooth pressure rise is created due to the heat release of the homogeneous combustion. An atmospheric combustion test rig is designed to investigate the auto-ignition behavior of relevant fuels under intermittent operation, currently up to a frequency of 2 Hz. Application of OH*– and dynamic pressure sensors allows for a spatially and time-resolved detection of ignition delay times and locations. Dimethyl ether (DME) is used as fuel since it exhibits reliable auto-ignition already at 920 K mixture temperature and ambient pressure. First, a model-based control algorithm is used to demonstrate that the fuel valve can produce arbitrary fuel profiles in the combustion tube. Next, the control algorithm is used to achieve the desired fuel stratification, resulting in a significant reduction in spatial variance of the auto-ignition delay times. This proves that the control approach is a useful tool for increasing the homogeneity of the auto-ignition. Journal of Engineering for Gas Turbines and Power Publication Title History February, 2017 | Volume 139 | Issue 2 http://gasturbinespower.asmedigitalcollection.asme.org/article.aspx?articleid=2537131&resultClick=1 10.1115/1.4034214 T. G.Reichel J. S.Schäpel P.Berndt R.King R.Klein C. O.Paschereit O.Christian article Wassmer2016 2016 5 30 GTRE-044 http://www.tum-ias.de/thermoacoustics2016/focus-impact.html D.Wassmer B.Schuermans C. O.Paschereit J. P.Moeck article Strangfeld2016 Journal of Fluid Mechanics 2016 4 793 79--108 http://journals.cambridge.org/article_S0022112016001269 1469-7645 10.1017/jfm.2016.126 C.Strangfeld H.Müller-Vahl C. N.Nayeri C. O.Paschereit D.Greenblatt article Schuele2016 Artificial Organs 2016 4 Paul S. Malchesky International Federation for Artificial Organs 1525-1594 10.1111/aor.12725 C. Y.Schüle B.Thamsen B.Blümel M.Lommel T.Karakaya C. O.Paschereit K.Affeld U.Kertzscher article Lennie_2016 AIAA SciTech Forum 2016 1 Conference Series http://dx.doi.org/10.2514/MWES16 Aerospace Research Central 10.2514/6.2016-1006 M.Lennie A.Bach G.Pechlivanoglou C. N.Nayeri C. O.Paschereit article Wendler_2016 Proceedings of ASME Turbo Expo 2016, June 13-17, 2016, Seoul, South Korea 2016 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy 11 Pages 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. Proceedings of ASME Turbo Expo 2016, June 13-17, 2016, Seoul, South Korea http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2555667 10.1115/GT2016-57184 J.Wendler D.Marten G.Pechlivanoglou C. N.Nayeri C. O.Paschereit article Marten2016 ASME 2016 139 2 9 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. Paper No: GTP-16-1286 http://gasturbinespower.asmedigitalcollection.asme.org/article.aspx?articleid=2541658&resultClick=3 10.1115/1.4034326 D.Marten S.Bianchini G.Pechlivanoglou F.Balduzzi C. N.Nayeri G.Ferrara C. O.Paschereit L.Ferrari article Stathopoulos2016b Journal of Engineering for Gas Turbines and Power 2016 139 4 8 http://gasturbinespower.asmedigitalcollection.asme.org/issue.aspx?journalid=120&issueid=935804 ASME P.Stathopoulos P.Kuhn J.Wendler T.Tanneberger S.Terhaar C. O.Paschereit C.Schmalhofer P.Griebel M.Aigner article Reichel2016 International Journal of Hydrogen Energy 2016 41 The impact of fuel momentum on the combustor flow field is studied experimentally in a swirl-stabilized, technically premixed hydrogen flame. The volumetric heating value of hydrogen is about 3.5 times lower compared to natural gas, which leads to significantly higher volumetric fuel flow rates at the same power level. This additional fuel momentum significantly alters the combustor flow field. Therefore, the fuel momentum also affects the combustor stability limits. Previous studies were mostly conducted at perfectly premixed conditions, where the fuel momentum does not alter the combustor flow field. In the current study, non-reacting and reacting combustor flow fields of a technically premixed model combustor injecting fuel in axial direction are recorded. Results reveal a strong impact of fuel momentum on axial velocity distribution at the mixing tube outlet and, thus, on the stability limits. Additionally, OH-PLIF recordings for different flow rates, air preheat temperatures, and equivalence ratios show that the axial location of the upstream flame front, xf, poses a telling estimator for flashback resistance. No flashback was observed when the upstream flame front was located downstream of the mixing tube. However, the flame tip always located upstream of the mixing tube outlet prior to flashback. A high value of xf was, thus, identified as a sufficient condition for flashback resistance. At the investigated conditions, xf is shifted downstream with increasing equivalence ratio due to the added momentum of the fuel flow, thereby superseding any parallel augmentation in the turbulent flame speed. This has been identified as the driving mechanism affecting the combustor stability limit. http://www.sciencedirect.com/science?_ob=ArticleListURL&_method=list&_ArticleListID=-1122493821&_sort=r&_st=13&view=c&md5=7c21464c1e012c6b3e2a6ac4e8b3c8e4&searchtype=a 03603199 10.1016/j.ijhydene.2016.11.018 T. G.Reichel C. O.Paschereit O.Christian article Schäpel2016 processes 2016 4(4) Changing the combustion process of a gas turbine from a constant-pressure to a pressure-increasing approximate constant-volume combustion (aCVC) is one of the most promising ways to increase the efficiency of turbines in the future. In this paper, a newly proposed method to achieve such an aCVC is considered. The so-called shockless explosion combustion (SEC) uses auto-ignition and a fuel stratification to achieve a spatially homogeneous ignition. The homogeneity of the ignition can be adjusted by the mixing of fuel and air. A proper filling profile, however, also depends on changing parameters, such as temperature, that cannot be measured in detail due to the harsh conditions inside the combustion tube. Therefore, a closed-loop control is required to obtain an adequate injection profile and to reject such unknown disturbances. For this, an optimization problem is set up and a novel formulation of a discrete extremum seeking controller is presented. By approximating the cost function with a parabola, the first derivative and a Hessian matrix are estimated, allowing the controller to use Newton steps to converge to the optimal control trajectory. The controller is applied to an atmospheric test rig, where the auto-ignition process can be investigated for single ignitions. In the set-up, dimethyl ether is injected into a preheated air stream using a controlled proportional valve. Optical measurements are used to evaluate the auto-ignition process and to show that using the extremum seeking control approach, the homogeneity of the ignition process can be increased significantly. shockless explosion combustion; constant volume combustion; extremum seeking control http://www.sciencedirect.com/science?_ob=ArticleListURL&_method=list&_ArticleListID=-1122493821&_sort=r&_st=13&view=c&md5=7c21464c1e012c6b3e2a6ac4e8b3c8e4&searchtype=a 03603199 10.3390/pr4040048 J. S.Schäpel T. G.Reichel R.Klein C. O.Paschereit O.Christian R.King article Holst_2016 Journal of Engineering for Gas Turbines and Power 2016 139 6 032604-1 - 032604-8 The present paper analyzes the effect of passive flow control (PFC) with respect to the retrofitting on small horizontal axis wind turbines (sHAWTs). We conducted extensive wind tunnel studies on a high performance low Reynolds airfoil using different PFC elements, i.e., vortex generators (VGs) and Gurney flaps (GF). qblade, an open source blade element momentum (BEM) code, is used to study the retrofitting potential of a simulated small wind turbine. The turbine design is presented and discussed. The simulations include the data and polars gained from the experiments and give further insight into the effects of PFC on sHAWTs. Therefore, several different blades were simulated using several variations of VG positions. This paper discusses their influence on the turbine performance. The authors especially focus on the startup performance as well as achieving increased power output at lower wind speeds. The vortex generators reduce the risk of laminar separation and enhance the lift in some configurations by more than 40 % at low Reynolds numbers. http://gasturbinespower.asmedigitalcollection.asme.org/article.aspx?articleid=2547692 0742-4795 10.1115/1.4034543 D.Holst G.Pechlivanoglou F.Wegner C. N.Nayeri C. O.Paschereit article Gray_2016 Proceedings of ASME Turbomachinery Technical Conference & Exposition. Seoul, South Korea, June 13–17, 2016 2016 Volume 4B: Combustion, Fuels and Emissions Paper No. GT2016-57813, pp. V04BT04A044 9 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. Proceedings of ASME Turbomachinery Technical Conference & Exposition. Seoul, South Korea, June 13 – 17, 2016 http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2555111 978-0-7918-4976-7 10.1115/gt2016-57813 J.Gray J.Vinkeloe J. P.Moeck C. O.Paschereit P.Stathopoulos P.Berndt R.Klein inbook Holst2016c 2016 54 - 57 http://sine.ni.com/cs/app/doc/p/id/cs-17418 Rahman J., Heinze R., VDE Verlag Begleitband zum 21. VIP-Kongress Mess-, Prüf- und Regelungstechnik in Virtuelle Instrumente in der Praxis 2016 978-3-8007-4441-1 D.Holst K.Thommes M.Schönlau C. N.Nayeri C. O.Paschereit inbook Kabiraj2016 2016 321-339 Webber Jr., L. C. and Ioana, C. and Marwan, N. Springer International Publishing Recurrence Plots for the Analysis of Combustion Dynamics 978-3-319-29922-8 10.1007/978-3-319-29922-8_17 L.Kabiraj A.Saurabh H.Nawroth C. O.Paschereit R. I.Sujith N.Karimi conference Marten2016a 2016 8 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. http://isromac-isimet.univ-lille1.fr/index.php?rubrique=abstract&num=24 ISROMAC 16 10.13140/RG.2.1.3116.5849 D.Marten M.Lennie C. N.Nayeri C. O.Paschereit incollection Nayeri2016b 2016 79 133-141 Dillmann, A. and Orellano, A. Springer International Publishing Lecture Notes in Applied and Computational Mechanics The Aerodynamics of Heavy Vehicles III English 978-3-319-20121-4 10.1007/978-3-319-20122-1_8 C. N.Nayeri C.Strangfeld C.Zellmann M.Schober A.Tietze C. O.Paschereit incollection Nayeri2016 2016 79 A. Dillmann, A. Orellano Springer International Publishing Lecture Notes in Applied and Computational Mechanics The Aerodynamics of Heavy Vehicles III: Trucks, Buses and Trains 978-3-319-20121-4 (Print) 978-3-319-20122-1 (Online) 1613-7736 10.1007/978-3-319-20122-1 C. N.Nayeri J.Glas C. O.Paschereit inproceedings Sieber2016 2016 ASME Paper GT2016-56591 Proceedings of ASME Turbo Expo 2016, June 13-17, 2016, Seoul, South Korea 10.1115/GT2016-56591 M.Sieber C. O.Paschereit K.Oberleithner inproceedings Wassmer2016 2016 ASME Paper GT2016-56571 Proceedings of ASME Turbo Expo 2016, June 13-17, 2016, Seoul, South Korea 10.1115/GT2016-56571 D.Wassmer B.Schuermans C. O.Paschereit J. P.Moeck inproceedings Kuhn_2016 2016 Volume 4B: Combustion, Fuels and Emissions 13 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 %. Paper No. GT2016-57686, pp. V04BT04A036 http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2555103 ASME Proceedings of ASME Turbo Expo 2016, June 13 - 17, 2016, Seoul, South Korea 10.1115/GT2016-57686 P.Kuhn J. P.Moeck C. O.Paschereit K.Oberleithner inproceedings rw2016:tschepe 2016 This paper shows that the interaction of an air stream (jet) coming from the outlet of a vehicle with the surrounding flow has an important impact on the pressure distribution in the outlet duct. Based on experimental investigations carried out in a wind tunnel it is shown that this interaction in most cases causes an additional counter pressure that has to be overcome by the acting fan. Depending on the parameter setting pressure differences in the order of several hundred Pascal can appear. Here, the most important parameter for this interaction turned out to be the momentum flux ratio of exhaust jet and cross-flow. This ratio is a result of the streams' fluid densities and velocities and is strongly affected by the near wall flow profile of the cross-flow upstream the outlet. Furthermore, the impact of geometry parameters such as the jet's exit shape is demonstrated. paper 44 http://dx.doi.org/10.4203/ccp.110.44 Pombo, J. Civil-Comp Press

Stirlingshire, United Kingdom

The Third International Conference on Railway Technology: Research, Development and Maintenance 1759-3433 10.4203/ccp.110.44 1 J.Tschepe M.Weise A.Tietze C. N.Nayeri C. O.Paschereit inproceedings Marten2016b 2016 9 11 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. Paper No. GT2016-56685, pp. V009T46A007 http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2555663 Seoul, South Korea, June 13–17, 2016 Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition ASMe 10.1115/GT2016-56685 D.Marten A.Bianchini G.Pechlivanoglou F.Balduzzi C. N.Nayeri G.Ferrara C. O.Paschereit L.Ferrari inproceedings Stathopoulos2016a 2016 Volume 4B: Combustion, Fuels and Emissions 11 It is generally accepted that combustion of hydrogen and natural gas mixtures will become more prevalent in the near future, to allow for a further penetration of renewables in the European power generation system. The current work aims at the demonstration of the advantages of steam dilution, when highly reactive combustible mixtures are used in a swirl-stabilized combustor. To this end, high-pressure experiments have been conducted with a generic swirl-stabilized combustor featuring axial air injection to increase flashback safety. The experiments have been conducted with two fuel mixtures, at various pressure levels up to 9 bar and at four levels of steam dilution up to 25 % steam-to-air mass flow ratio. Natural gas has been used as a reference fuel, whereas a mixture of natural gas and hydrogen (10 % hydrogen by mass) represented an upper limit of hydrogen concentration in a natural gas network with hydrogen enrichment. The results of the emissions measurements are presented along with a reactor network model. The latter is applied as a means to qualitatively understand the chemical processes responsible for the observed emissions and their trends with increasing pressure and steam injection. Paper No. GT2016-57745, pp. V04BT04A040 http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2555107&resultClick=3 ASME Proceedings of ASME Turbo Expo 2016, June 13-17, 2016, Seoul, South Korea 10.1115/GT2016-57745 P.Stathopoulos P.Kuhn J.Wendler T.Tanneberger S.Terhaar C. O.Paschereit C.Schmalhofer P.Griebel M.Aigner inproceedings Holst2016a 2016 9 11 The present paper analyzes the effect of passive flow control (PFC) with respect to the retrofitting on small horizontal axis wind turbines (sHAWT). We conducted extensive wind tunnel studies on an high performance low Reynolds airfoil using different PFC elements, i.e. vortex generators (VGs) and Gurney flaps. QBlade, an open source Blade Element Momentum (BEM) code, is used to study the retrofitting potential of a simulated small wind turbine. The turbine design is presented and discussed. The simulations include the data and polars gained from the experiments and give further insight into the effects of PFC on sHAWT. Therefore several different blades were simulated using several variations of VG positions. This paper discusses their influence on the turbine performance. The authors focus especially on the start-up performance as well as achieving increased power output at lower wind speeds. The vortex generators reduce the risk of laminar separation and enhance the lift in some configurations by more than 40% at low Reynolds numbers. Paper No. GT2016-56679 ASME Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy 10.1115/GT2016-56679 D.Holst G.Pechlivanoglou F.Wegner C. N.Nayeri C. O.Paschereit inproceedings Wieser2016 2016 12 http://arc.aiaa.org/doi/10.2514/6.2016-1778 ARC AIAA 54th AIAA Aerospace Sciences Meeting 10.2514/6.2016-1778 D.Wieser S.Bonitz C. N.Nayeri C. O.Paschereit A.Broniewicz L.Larsson L.Löfdahl inproceedings Host2016b 2016 9 10 Small horizontal axis wind turbines (sHAWTs) are mostly designed by smaller companies with no or just small possibilities of aerodynamic testing and hence, airfoil selection is often based on published performance data and minimal or no experimental testing from the blade designer’s side. This paper focuses on the aerodynamic consequences resulting from an unqualified airfoil selection and accumulating surface soiling. The high performance low Reynolds profile FX 63-137 is compared to an Eppler-338 wing section as well as to a high performance utility scale wind turbine airfoil, AH 93-W-174 -1ex. We extensively investigated these three different airfoils within the low Reynolds regime between 50,000 and 200,000. This regime is especially important for the starting behavior of a wind turbine, i.e. a quick speed up, and is crucial for small wind turbines because they have more frequent start/stop events. A Reynolds number of 200 k is additionally the operational regime of some sHAWT under the 5–10 kW level. The present study discusses not only the low Reynolds performance of the smooth profiles but investigates the influence of surface soiling. This ranges from 2D disturbances, such as a 0.2mm thin tripwire or several zigzag tapes, up to the simulation of massive sand build up by covering the entire leading edge region with a 40 grit sand paper. The experiments reveal that even small surface soiling has an impact and massive roughness leads in some cases to the loss of 50% in lift coefficient. The experimental data is used to simulate a sHAWT in different stages of debris. While the peak power was reduced by two thirds compared to the clean configuration the annual energy production has halved under certain conditions. http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2555661 ASME Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition 10.1115/GT2016-56377 D.Holst G.Pechlivanoglou C. T.Kohlrausch C. N.Nayeri C. O.Paschereit inproceedings Reichel2016 2016 4B Approximate constant volume combustion (aCVC) is a promising way to achieve a step change in the efficiency of gas turbines. This work investigates a recently proposed approach to implement aCVC in a gas turbine combustion system: shockless explosion combustion (SEC). The new concept overcomes several disadvantages such as sharp pressure transitions, entropy generation due to shock waves, and exergy losses due to kinetic energy which are associated with other aCVC approaches like, e.g., pulsed detonation combustion. The combustion is controlled via the the fuel/air mixture distribution which is adjusted such that the entire fuel/air volume undergoes a spatially quasi-homogeneous autoignition. Accordingly, no shock waves occur and the losses associated with a detonation wave are not present in the proposed system. Instead, a smooth pressure rise is created due to the heat release of the homogeneous combustion. An atmospheric combustion test rig is designed to investigate the autoignition behavior of relevant fuels under intermittent operation, currently up to a frequency of 2Hz. Application of OH*- and dynamic pressure sensors allows for a spatially- and time-resolved detection of ignition delay times and locations. Dimethyl ether (DME) is used as fuel since it exhibits reliable autoignition already at 920K mixture temperature and ambient pressure. First, a model-based control algorithm is used to demonstrate that the fuel valve can produce arbitrary fuel profiles in the combustion tube. Next, the control algorithm is used to achieve the desired fuel stratification, resulting in a significant reduction in spatial variance of the auto-ignition delay times. This proves that the control approach is a useful tool for increasing the homogeneity of the autoignition. http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2555102 ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition 10.1115/GT2016-57680 T. G.Reichel J. S.Schäpel P.Berndt R.King R.Klein C. O.Paschereit O.Christian inproceedings rw2016:tschep2 2016 This paper gives an overview on different experimental methods for the measurement of the aerodynamic drag of railroad vehicles in general as well as on the measurement of drag of submerged bodies in water in particular. It is shown that water based drag measurements with moving railroad models are very promising in terms of overcoming disadvantages in wind tunnel testing with scaled models. For this reason, a test setup in the water towing tank of the Technical University of Berlin is being developed to adapt the physical boundary conditions including high Reynolds numbers for more accurate results and the possibility to investigate full length model train compositions. Advantages and limitations of these experiments in water are discussed and preliminary results are presented. paper 49 http://dx.doi.org/10.4203/ccp.110.49 Pombo, J. Civil-Comp Press

Stirlingshire, United Kingdom

The Third International Conference on Railway Technology: Research, Development and Maintenance 1759-3433 10.4203/ccp.110.49 1 J.Tschepe C. N.Nayeri H.-J.Schmidt C. O.Paschereit techreport Wieser2016 2016 2016-01-1582 Flow visualization techniques are widely used in aerodynamics to investigate the surface trace pattern. In this experimental investigation, the surface flow pattern over the rear end of a full-scale passenger car is studied using tufts. The movement of the tufts is recorded with a DSLR still camera, which continuously takes pictures. A novel and efficient tuft image processing algorithm has been developed to extract the tuft orientations in each image. This allows the extraction of the mean tuft angle and other such statistics. From the extracted tuft angles, streamline plots are created to identify points of interest, such as saddle points as well as separation and reattachment lines. Furthermore, the information about the tuft orientation in each time step allows studying steady and unsteady flow phenomena. Hence, the tuft image processing algorithm provides more detailed information about the surface flow than the traditional tuft method. The main advantages over other flow visualization methods, such as oil paint, is that experimental facilities are not contaminated and statistical data can be extracted.The investigated surface pattern shows a symmetric flow on the entire rear end section of the passenger car. The flow field on the roof, backlight, and upper trunk deck is attached almost everywhere. However, two small regions indicate the presence of two counter-rotating vortices at the lower edge of the backlight (rear window). Those vortices are also detectable in the distribution of the tuft angle standard deviation. A bifurcation line is present at each side of the trunk due to the streamwise vortices originating at the C-pillars. The tuft streamlines created with this novel tuft method are compared to a standard oil paint flow visualization to validate the calculated tuft flow pattern. A critical comparison between the methods confirms that the flow tuft analysis algorithm functions flawlessly as a highly detailed flow analysis tool without the mess of oil paint. http://papers.sae.org/2016-01-1582/ SAE Technical Paper, SAE 2016 World Congress and Exhibition Technical Paper 10.4271/2016-01-1582 D.Wieser S.Bonitz L.Löfdahl A.Broniewicz C. N.Nayeri C. O.Paschereit L.Larsson article Vahl2015c Experiments in Fluids 2015 2 56 38 Springer Berlin Heidelberg 0723-4864 (print), 1432-1114 (online) 10.1007/s00348-014-1889-z H.Müller-Vahl C. N.Nayeri C. O.Paschereit D.Greenblatt article Cosic2014bb Journal of Sound and Vibration 2015 335 1-18 0022-460X /10.1016/j.jsv.2014.08.025 B.Ćosić D.Wassmer S.Terhaar C. O.Paschereit article Schimek2015 Journal of Engineering for Gas Turbines and Power 2015 137 8 GTP-14-1525 081501-1/10 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. http://gasturbinespower.asmedigitalcollection.asme.org/data/Journals/JETPEZ/0/GTP-14-1525.pdf 10.1115/1.4029368 S.Schimek B.Ćosić J. P.Moeck S.Terhaar C. O.Paschereit article Kabiraj2015 Chaos: An Interdisciplinary Journal of Nonlinear Science 2015 25 2 - http://scitation.aip.org/content/aip/journal/chaos/25/2/10.1063/1.4906943 10.1063/1.4906943 L.Kabiraj A.Saurabh N.Karimi A.Sailor E.Mastorakos A. P.Dowling C. O.Paschereit article Kabiraj2015 Physical Review E 2015 92 4 We experimentally investigated the noise-induced dynamics of a prototypical thermoacoustic system undergoing a subcritical Hopf bifurcation to limit cycle oscillations. The study was performed prior to the bistable regime. Analysis of the characteristics of pressure oscillations in the combustor and fluctuations in the heat release rate from the flame—the two physical entities involved in thermoacoustic coupling—at increasing levels of noise indicated precursors to the Hopf bifurcation. These precursors were further identified to be a result of coherence resonance. http://dx.doi.org/10.1103/PhysRevE.92.042909 American Physical Society ({APS}) 10.1103/physreve.92.042909 L.Kabiraj R.Steinert A.Saurabh C. O.Paschereit article Nayeri2015 DEWEK 2015 2015 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. http://15.dewek.de/fileadmin/downloads/Book_of_Abstracts_2015.pdf DEWI C. N.Nayeri S.Vey D.Marten G.Pechlivanoglu C. O.Paschereit article Nayeri2015 AIAA Journal 2015 53 2 277-295 10.2514/1.J053090 H.Mueller-Vahl C.Strangfeld C. N.Nayeri C. O.Paschereit D.Greenblatt article Niether2015a Journal of Turbomachinery 2015 137 6 061003 (10 pages) http://asmedigitalcollection.asme.org/data/Journals/JOTUEI/0/TURBO-14-1229.pdf 0889-504X 10.1115/1.4028654 S.Niether B.Bobusch D.Marten G.Pechlivanoglou C. N.Nayeri C. O.Paschereit article Fischer2015 DEWEK 2015 2015 The development of a medium scale research wind turbine is a part of the research project PAK 780 funded by the German Science Foundation (DFG). In this project six universities from all over Germany join forces and pursue fundamental research in the field of wind turbine aerodynamics, inflow turbulence as well as wake and flow control. The Modular Research Wind Turbine (MoReWiT) design and development is an integral part of this research program designed to assist the research tasks of all project partners. The PAK 780 project consists of HFI TU Berlin, RWTH Aachen, Univ. of Oldenburg, Univ. of Stuttgart and TU Darmstadt and it is one of the major DFG funded projects in wind energy. Book of abstracts 2015 http://15.dewek.de/fileadmin/downloads/Book_of_Abstracts_2015.pdf DEWI J.Fischer O.Eisele G.Pichlivanoglou S.Vey C. N.Nayeri C. O.Paschereit article Schmidt2015b Experiments in Fluids 2015 56 7 Springer Berlin Heidelberg 0723-4864 (print), 1432-1114 (online) 10.1007/s00348-015-2018-3 H.-J.Schmidt R.Woszidlo C. N.Nayeri C. O.Paschereit article Hoffmann2015 SAE Int. J. Passeng. Cars - Mech. Syst. 2015 8 2 2015-01-2890 705-712 The potential of drag reduction on a generic model of a heavy vehicle using base flaps operated in combination with flow control devices is investigated experimentally. Base flaps are well known as drag reduction devices for bluff bodies and heavy road vehicles. However, for optimal performance their deflection angle should typically not exceed 12°. In this paper the primary goal is to increase the usable range of the deflection angles by applying flow control. The secondary goal is to find the most suitable method for flow control. A comparison is made between triangular vortex generators and fluidic oscillators as passive and active flow control methods, respectively. Vortex generators have the advantage of being very simple devices but produce drag. Fluidic oscillators are also quite simple devices but require additional air supply. Their advantages are that they can be activated when needed and that they do not generate additional drag. The wind tunnel model used corresponds to the geometrical dimensions of a 10% scaled model yielding a Reynolds number of 7·105. Various flap angles with a length of 100mm were attached to the base. Other geometrical parameters such as the height of the vortex generators were also varied as well as their axial position. The results show that base flaps deflected by 20° combined with vortex generators reduce drag by 26% compared to the baseline. At deflection angles of 22.5° the passive and active concepts show similar drag reduction. Furthermore, possibilities for performance improvement of the active concept are identified. 10.4271/2015-01-2890 F.Hoffmann H. J.Schmidt C. N.Nayeri C. O.Paschereit article Rukes2015a Exp. Fluids 2015 56 10 accepted for publication 10.1007/s00348-015-2066-8 L.Rukes M.Sieber C. O.Paschereit K.Oberleithner article Paredes2015b Journal of Engineering for Gas Turbines and Power 2015 GTP-15-1320 ASME 0742-4795 (online), 1528-8919 (print) 10.1115/1.4031183 P.Paredes V.Theofilis S.Terhaar K.Oberleithner C. O.Paschereit article Marten2015 Journal of Engineering for Gas Turbines and Power 2015 137 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 GTP-15-1421 http://gasturbinespower.asmedigitalcollection.asme.org/article.aspx?articleid=2467296 Journal of Engineering for Gas Turbines and Power 10.1115/1.4031872 D.Marten M.Lennie G.Pechlivanoglou C. N.Nayeri C. O.Paschereit article Reichel2015c Journal of Engineering for Gas Turbines and Power 2015 137 7 GTP-14-1522 071503 (9 pages) 10.1115/1.4029119 T. G.Reichel S.Terhaar C. O.Paschereit article Reichel2015b Journal of Engineering for Gas Turbines and Power 2015 137 11 GTP-15-1263 111513 (10 pages) ASME 0742-4795 (online), 1528-8919 (print) 10.1115/1.4031181​ T. G.Reichel K.Göckeler C. O.Paschereit article Terhaar2015b Procedia IUTAM 2015 14 553 - 562 IUTAM_ABCM Symposium on Laminar Turbulent Transition Turbulent swirling flow http://www.sciencedirect.com/science/article/pii/S2210983815001054 2210-9838 10.1016/j.piutam.2015.03.079 S.Terhaar P.Paredes K.Oberleithner V.Theofilis C. O.Paschereit article TerhaarOP2014 Proceedings of the Combustion Institute 2015 35 3 3347-3354 15407489 10.1016/j.proci.2014.07.035 S.Terhaar K.Oberleithner C. O.Paschereit article Goeckeler2015 Journal of Engineering for Gas Turbines and Power 2015 137 3 GTP-14-1366 031503 (8 pages) Humidified gas turbines using steam generated from excess heat feature increased cycle efficiencies. Injecting the steam into the combustor reduces NOx emissions, flame temperatures, and burning velocities, promising a clean and stable combustion of highly reactive fuels such as hydrogen or hydrogen–methane blends. This study presents laminar burning velocities for methane and hydrogen-enriched methane (10 mol. % and 50 mol. %) at steam contents up to 30% of the air mass flow. Experiments were conducted on prismatic Bunsen flames stabilized on a slot-burner, employing OH planar laser-induced fluorescence (OH-PLIF) as an indicator for flame front areas. The experimental burning velocities agree well with results from one-dimensional simulations using the GRI 3.0 mechanism. Burning velocities reduce nonlinearly with ascending steam mole fractions and more rapid compared to simulations using “virtual H2O” stemming from a chemical influence on reactions. Hydrogen enrichment increases burning velocities, extending the flammability range toward leaner and more humid mixtures. Additionally, measured NOx and CO emissions reveal a strong reduction in NOx emissions for increasing steam dilution rates, whereas CO curves are shifted toward higher equivalence ratios. http://gasturbinespower.asmedigitalcollection.asme.org/data/Journals/JETPEZ/930944/gtp_137_03_031503.pdf 0742-4795 10.1115/1.4028460 K.Göckeler O.Krüger C. O.Paschereit article Wieser2015d SAE Int. J. Passeng. Cars - Mech. Syst. 2015 8 2 2015-01-1540 687-702 Abstract The effect of an active flow control method is investigated on a 1:4 scale realistic vehicle model called DrivAer with notchback geometry. The wind tunnel experiments are conducted at a Reynolds number of Re=3.0·106. Fluidic oscillators are applied at the c-pillars and at the upper rear edge of the window. The actuators are installed inside the hollow designed model emitting a high frequency sweeping jet. The spacing of the actuators, the mass flow rate, and the position of actuation are varied. The effect of the active flow control on the car is investigated with force and surface pressure measurements. The surface trace pattern is visualized with tufts for the active flow control cases and the baseline case. A tuft algorithm analyzes provides statistical data of the flow angles. Moreover, particle image velocimetry measurements are performed in the plane of symmetry for β=0° to capture the flow field at the rear end and the wake. 10.4271/2015-01-1540 D.Wieser H.Lang C. N.Nayeri C. O.Paschereit article Thamsen2015 Artificial Organs (International Society for Artificial Organs, ISAO) 2015 39 8 651--659 Blood trauma, Left ventricular assist devices, Rotary blood pumps, Computational fluid dynamics, Blood damage 1525-1594 10.1111/aor.12542 B.Thamsen B.Blümel J.Schaller C. O.Paschereit K.Affeld L.Goubergrits U.Kertzscher article Darvish2015a Journal of Turbomachinery 2015 137 10 TURBO-15-1063 101500-1 (9 pages) ASME 0889-504X 10.1115/1.4030498 M.Darvish S.Frank C. O.Paschereit article Spiegelberg2015 DEWEK2015 2015 As wind turbines have developed in size, there is a growing need for an easy and safe transport of spare parts and materials inside the nacelle, due to longer transport ways. Besides reducing the production and installation costs, the third also very important factor for the industry is the cost of operation and maintenance. If time of maintenance could be reduced and made more efficient, with less risk of accidents, the industry would save cost. Terex has, with its brand Demag, in an innovative way developed a new solution for the wind industry, based on reliable technology. 1.2 Challenges How do you transport parts inside the large nacelles of today and tomorrow, when parts must be transported longer ways with the risk of accidents? Till now, a simple jib crane mounted in the back end of the nacelle was sufficient, but the reach of such a crane is limited in the new turbine sizes over 5 MW. Secondly when every minute is cost, also waiting time for lifting and lowering of parts with chain hoist, becomes crucial as towers now can be up to 180 meters high. Furthermore, as turbines are installed offshore, the need for a crane system with no hydraulics is important to keep maintenance cost as low as possible. http://15.dewek.de/fileadmin/downloads/Book_of_Abstracts_2015.pdf H.Spiegelberg M.Lennie G.Pechlivanoglou article Ostermann2015b AIAA Journal 2015 53 8 2359--2368 0001-1452 10.2514/1.J053717 F.Ostermann R.Woszidlo C. N.Nayeri C. O.Paschereit article Kabiraj2015b AIAA Journal 2015 53 5 1199-1210 0001-1452 10.2514/1.J053285 L.Kabiraj A.Saurabh H.Nawroth C. O.Paschereit article Stathopoulos2015b Applied Energy 2015 154 438-–446 Elsevier 0306-2619 10.1016/j.apenergy.2015.05.034 P.Stathopoulos C. O.Paschereit article Oberleithner2013d Combustion and Flame 2015 162 1 86-99 Swirl flame http://www.sciencedirect.com/science/article/pii/S0010218014002077 0010-2180 10.1016/j.combustflame.2014.07.012 K.Oberleithner S.Schimek C. O.Paschereit article Sieber2015a ArXiv e-prints 2015 http://arxiv.org/pdf/1508.04642 M.Sieber K.Oberleithner C. O.Paschereit article Oberleithner2015b Procedia IUTAM 2015 14 141 - 146 IUTAM_ABCM Symposium on Laminar Turbulent Transition linear stability analysis http://www.sciencedirect.com/science/article/pii/S2210983815000607 2210-9838 10.1016/j.piutam.2015.03.034 K.Oberleithner C. O.Paschereit J.Soria article Woszidlo2015 Experiments in Fluids 2015 56 6 0723-4864 (print), 1432-1114 (online) 10.1007/s00348-015-1993-8 R.Woszidlo F.Ostermann C. N.Nayeri C. O.Paschereit article Terhaar2014c Journal of Propulsion and Power 2015 31 1 219-229 10.2514/1.B35217 S.Terhaar T. G.Reichel C.Schrödinger L.Rukes K.Oberleithner C. O.Paschereit article Holst2015 Journal of Engineering for Gas Turbines and Power 2015 138 6 062602--062602 http://dx.doi.org/10.1115/1.4031709 ASME 0742-4795 10.1115/1.4031709 D.Holst A.Bach C. N.Nayeri C. O.Paschereit G.Pechlivanoglou article Xydis2015 Challenges 2015 6 188--201 wind; waste heat recovery; district heating http://www.mdpi.com/2078-1547/6/2/188 challenges-nayeri-2015.pdf 2078-1547 10.3390/challe6020188 G.Xydis G.Pechlivanoglou C. N.Nayeri conference Stathopoulos2015 2015 11 Toranomon Hills, Tokyo, Japan International Gas Turbine Congress IGTC Nov 15-20, 2015 P.Stathopoulos J.Vinkeloe C. O.Paschereit incollection Gray2015 2015 127 265-279 Rudibert King Springer Notes on Numerical Fluid Mechanics and Multidisciplinary Design Active Flow and Combustion Control 2014 978-3-319-11966-3 10.1007/978-3-319-11967-0 J.Gray C. O.Paschereit J. P.Moeck incollection Oevermann2015 2015 127 213-227 Rudibert King Springer Notes on Numerical Fluid Mechanics and Multidisciplinary Design Active Flow and Combustion Control 2014 978-3-319-11966-3 10.1007/978-3-319-11967-0 M.Oevermann C.Schrödinger C. O.Paschereit incollection Bobusch2015a 2015 127 281-297 Rudibert King Springer Notes on Numerical Fluid Mechanics and Multidisciplinary Design Active Flow and Combustion Control 2014 978-3-319-11966-3 10.1007/978-3-319-11967-0 B.Bobusch P.Berndt C. O.Paschereit R.Klein inproceedings Bluemel2015 2015 6 25 Proceedings of 33th ANSYS Conference & CADFEM Users Meeting, Jun 24-26, Bremen, Germany Bremen, Germany ANSYS Conference & 33th CADFEM Users Meeting June 24-26, 2015 3-937523-12-X B.Blümel C. O.Paschereit B.Thamsen J.Schaller inproceedings Lennie2015a 2015 ASME Paper GT2015-43249 V009T46A018 (13 pages) Proceedings of ASME Turbo Expo 2015, June 15-19, 2015, Montreal, Quebec, Canada 978-0-7918-5680-2 10.1115/GT2015-43249 M.Lennie G.Pechlivanoglou D.Marten C. N.Nayeri C. O.Paschereit inproceedings Schaepel2015a 2015 ASME Paper GT2015-42027 V04AT04A005 (12 pages) Proceedings of ASME Turbo Expo 2015, June 15-19, 2015, Montreal, Quebec, Canada 978-0-7918-5668-0 10.1115/GT2015-42027 J. S.Schäpel R.King B.Bobusch J. P.Moeck C. O.Paschereit inproceedings Schwadtke2015 2015 218-221 VDE Verlag Virtuelle Instrumente in der Praxis 2015: Begleitband zum 20. VIP-Kongress 978-3800736690 U.Schwadtke D.Holst C. O.Paschereit inproceedings Schimek2015c 2015 ASME Paper GT2015-43149 V04BT04A007 (7 pages) Proceedings of ASME Turbo Expo 2015, June 15-19, 2015, Montreal, Quebec, Canada 978-0-7918-5669-7 10.1115/GT2015-43149 S.Schimek P.Stathopoulos T.Tanneberger C. O.Paschereit inproceedings Marten2015a 2015 AIAA paper no. 2015-3390 AIAA Aviation, 33rd AIAA Applied Aerodynamics Conference, June 22-26, 2015, Dallas, Texas, USA 978-1-62410-363-6 10.2514/6.2015-3390 D.Marten H.Spiegelberg G.Pechlivanoglou C. N.Nayeri C. O.Paschereit T.Cameron inproceedings Kuhn2015a 2015 ASME Paper GT2015-43375 V04BT04A024 (11 pages) Proceedings of ASME Turbo Expo 2015, June 15-19, 2015, Montreal, Quebec, Canada 978-0-7918-5669-7 10.1115/GT2015-43375 P.Kuhn S.Terhaar T. G.Reichel C. O.Paschereit inproceedings Gray2015a 2015 AIAA paper no. 2015-1351 AIAA SciTech, 53rd Aerospace Sciences Meeting, 5-9 January, Kissimmee, Florida, USA 10.2514/6.2015-1351 J.Gray J. P.Moeck C. O.Paschereit inproceedings Nawroth2015a 2015 AIAA paper no. 2015-0303 AIAA SciTech, 53rd Aerospace Sciences Meeting, 5-9 January, Kissimmee, Florida, USA 10.2514/6.2015-0303 H.Nawroth C. O.Paschereit inproceedings Vey2015a 2015 AIAA paper no. 2015-3392 AIAA Aviation, 33rd AIAA Applied Aerodynamics Conference, June 22-26, 2015, Dallas, Texas, USA 978-1-62410-363-6 10.2514/6.2015-3392 S.Vey D.Marten G.Pechlivanoglou C. N.Nayeri C. O.Paschereit inproceedings Ostermann2015a 2015 AIAA paper no. 2015-0781 AIAA SciTech, 53rd Aerospace Sciences Meeting, 5-9 January, Kissimmee , Florida, USA 10.2514/6.2015-0781 F.Ostermann R.Woszidlo C. N.Nayeri C. O.Paschereit inproceedings VonGosen.2015 2015 AIAA paper no. 2015-0782 AIAA SciTech, 53rd Aerospace Sciences Meeting, 5-9 January, Kissimmee , Florida, USA 10.2514/6.2015-0782 F.Von Gosen F.Ostermann R.Woszidlo C. N.Nayeri C. O.Paschereit inproceedings Bach2015a 2015 A.Bach R.Berg G.Pechlivanoglou C. N.Nayeri C. O.Paschereit inproceedings Bach2015b 2015 AIAA paper no. 2015-1270 AIAA SciTech, 53rd Aerospace Sciences Meeting, 5-9 January, Kissimmee, Florida, USA 10.2514/6.2015-1270 A.Bach R.Berg C. N.Nayeri C. O.Paschereit inproceedings Schmidt2015a 2015 AIAA paper no. 2015-0786 AIAA SciTech, 53rd Aerospace Sciences Meeting, 5-9 January, Kissimmee, Florida, USA 10.2514/6.2015-0786 H.-J.Schmidt R.Woszidlo C. N.Nayeri C. O.Paschereit inproceedings Dolan2015a 2015 AIAA paper no. 2015-0929 AIAA SciTech, 53rd Aerospace Sciences Meeting, 5-9 January, Kissimmee, Florida, USA 10.2514/6.2015-0929 B.Dolan R.Gomez H.Nawroth S.Pack E. J.Gutmark inproceedings Wieser2015a 2015 AIAA paper no. 2015-1236 AIAA SciTech, 53rd Aerospace Sciences Meeting, 5-9 January, Kissimmee, Florida, USA 10.2514/6.2015-3392 D.Wieser C. N.Nayeri C. O.Paschereit inproceedings Nawroth2015a 2015 AIAA paper no. 2015-2316 AIAA Aviation, 45th AIAA Fluid Dynamics Conference, June 22-25, 2015, Dallas, Texas, USA 978-1-62410-362-9 10.2514/6.2015-2316 H.Nawroth C. O.Paschereit inproceedings Paredes2015a 2015 ASME Paper GT2015-44173 V04BT04A070 (10 pages) Proceedings of ASME Turbo Expo 2015, June 15-19, 2015, Montreal, Quebec, Canada 978-0-7918-5669-7 10.1115/GT2015-44173 P.Paredes V.Theofilis S.Terhaar K.Oberleithner C. O.Paschereit inproceedings Marten2015a 2015 ASME Paper GT2015-43265 V009T46A019 (11 pages) Proceedings of ASME Turbo Expo 2015, June 15-19, 2015, Montreal, Quebec, Canada 978-0-7918-5680-2 10.1115/GT2015-43265 D.Marten M.Lennie G.Pechlivanoglou C. N.Nayeri C. O.Paschereit inproceedings Reichel2015d 2015 ASME Paper GT2015-42491 V04AT04A036 (13 pages) Proceedings of ASME Turbo Expo 2015, June 15-19, 2015, Montreal, Quebec, Canada 978-0-7918-5668-0 10.1115/GT2015-42491 T. G.Reichel K.Göckeler C. O.Paschereit inproceedings Huang2015a 2015 AIAA paper no. 2015-2310 AIAA Aviation, 45th AIAA Fluid Dynamics Conference, June 22-25, 2015, Dallas, Texas, USA 978-1-62410-362-9 10.2514/6.2015-2310 X.Huang S.Vey M.Meinke W.Schroeder G.Pechlivanoglou C. N.Nayeri C. O.Paschereit inproceedings Tanneberger2015a 2015 ASME Paper GT2015-43382 V04BT04A026 (12 pages) Proceedings of ASME Turbo Expo 2015, June 15-19, 2015, Montreal, Quebec, Canada 978-0-7918-5669-7 10.1115/GT2015-43382 T.Tanneberger T. G.Reichel O.Krüger TerhaarS. C. O.Paschereit inproceedings Stathopoulos2015a 2015 ASME Paper GT2015-42274 V003T20A003 (13 pages) Proceedings of ASME Turbo Expo 2015, June 15-19, 2015, Montreal, Quebec, Canada 978-0-7918-5667-3 10.1115/GT2015-42274 P.Stathopoulos C. O.Paschereit inproceedings Rukes2015a 2015 AIAA paper no. 2015-0302 AIAA SciTech, 53rd Aerospace Sciences Meeting, 5-9 January, Kissimmee, Florida, USA 10.2514/6.2015-0302 L.Rukes M.Sieber K.Oberleithner C. N.Nayeri C. O.Paschereit inproceedings Castro2015a 2015 ASME Paper GT2015-43198 V009T46A016 (12 pages) Proceedings of ASME Turbo Expo 2015, June 15-19, 2015, Montreal, Quebec, Canada 978-0-7918-5680-2 10.1115/GT2015-43198 O.Castro M.Lennie G.Pechlivanoglou C. N.Nayeri C. O.Paschereit inproceedings Strangfeld2015b 2015 AIAA paper no. 2015-3071 AIAA Aviation, 45th AIAA Fluid Dynamics Conference, June 22-25, 2015, Dallas, Texas, USA 978-1-62410-362-9 10.2514/6.2015-3071 C.Strangfeld C. L.Rumsey H.Müller-Vahl D.Greenblatt C. N.Nayeri C. O.Paschereit inproceedings Vey2015a 2015 ASME Paper GT2015-43407 V009T46A021 (6 pages) Results from a quantitative tuft flow visualization of a utility scale wind turbine undergoing a yaw movement are presented. Based on the turbine’s SCADA data suitable pre- and post-yaw timeframes were defined and the surface flowfields were analysed. A distinct asymmetry between the surface flow patterns of the 90° and 270° azimutal blade positions was observed in the pre-yaw timeframe. After the turbine yawed back into the wind the symmetry was restored. Yaw-misalignment is a source of dynamic loads which limit a turbine’s life time. The characterization of the involved flow structures and their dynamics is an essential step towards possible future load alleviation techniques. The quantitative tuft flow visualization technique is a measurement tool that can be used to assess the surface flow field. Proceedings of ASME Turbo Expo 2015, June 15-19, 2015, Montreal, Quebec, Canada 978-0-7918-5680-2 10.1115/GT2015-43407 S.Vey H. M.Lang C. N.Nayeri C. O.Paschereit G.Pechlivanoglou G.Weinzierl inproceedings Holst2015a 2015 ASME Paper GT2015-43220 V009T46A017 (13 pages) The results of stereo Particle-Image-Velocimetry measurements are presented in this paper to gain further insight into the wake of a finite width Gurney flap. It is attached to an FX 63-137 airfoil which is known for a very good performance at low Reynolds numbers and is therefore used for small wind turbines and is most appropriate for tests in the low speed wind tunnel presented in this study. The Gurney flaps are a promising concept for load control on wind turbines but can have adverse side effects, e.g. shedding of additional vortices. The investigation focuses on frequencies and velocity distributions in the wake as well as on the structure of the induced tip vortices. Phase averaged velocity fields are derived of a Proper-Orthogonal-Decomposition based on the stereo PIV measurements. Additional hot-wire measurements were conducted to analyze the fluctuations downstream of the finite width Gurney flaps. Experiments indicate a general tip vortex structure that is independent from flap length but altered by the periodic shedding downstream of the flap. The influence of Gurney flaps on a small wind turbine is investigated by simulating a small 40 kW turbine in Q-Blade. They can serve as power control without the need of an active pitch system and the starting performance is additionally improved. The application of Gurney flaps imply tonal frequencies in the wake of the blade. Simulation results are used to estimate the resulting frequencies. However, the solution of Gurney flaps is a good candidate for large scale wind turbine implementation as well. A FAST simulation of the NREL 5MW turbine is used to generate realistic time series of the lift. The estimations of control capabilities predict a reduction in the standard deviation of the lift of up to 65%. Therefore finite width Gurney flaps are promising to extend the lifetime of future wind turbines. Proceedings of ASME Turbo Expo 2015, June 15-19, 2015, Montreal, Quebec, Canada 978-0-7918-5680-2 10.1115/GT2015-43220 D.Holst A.Bach C. N.Nayeri C. O.Paschereit G.Pechlivanoglou inproceedings Bach2015b 2015 AIAA paper no. 2015-1271 AIAA SciTech, 53rd Aerospace Sciences Meeting, 5-9 January, Kissimmee , Florida, USA 10.2514/6.2015-1271 A.Bach G.Pechlivanoglou C. N.Nayeri C. O.Paschereit article Oberleithner2013c Journal of Fluid Mechanics 2014 2 741 156--199 http://journals.cambridge.org/article_S0022112013006691 1469-7645 10.1017/jfm.2013.669 K.Oberleithner C. O.Paschereit I.Wygnanski article PaschereitTCO2014 Journal of Fluid Science and Technology 2014 9 3 1-14 https://www.jstage.jst.go.jp/article/jfst/9/3/9_2014jfst0024/_pdf 10.1299/jfst.2014jfst0024 C. O.Paschereit S.Terhaar B.Ćosić K.Oberleithner article Strangfeld2014b SAE Int. J. Passeng. Cars - Mech. Syst. 2014 7 2 2014-01-0613 682-691 http://papers.sae.org/2014-01-0613/ Society of Automobile Engineers SAE 2014 World Congress & Exhibition, October 21-22, Detroit, Michigan, USA 10.4271/2014-01-0613 D.Wieser H.-J.Schmidt S.Müller C.Strangfeld C. N.Nayeri C. O.Paschereit article Vey2014a Journal of Physics: Conference Series 2014 524 1 http://iopscience.iop.org/1742-6596/524/1/012011/pdf/1742-6596_524_1_012011.pdf The Science of Making Torque from Wind 2014 10.1088/1742-6596/524/1/012011 S.Vey H. M.Lang C. N.Nayeri C. O.Paschereit G.Pechlivanoglou article Bach2014c Journal of Physics: Conference Series 2014 524 1 http://iopscience.iop.org/1742-6596/524/1/012082/pdf/1742-6596_524_1_012082.pdf The Science of Making Torque from Wind 2014 10.1088/1742-6596/524/1/012082 A.Bach M.Lennie G.Pechlivanoglou C. N.Nayeri C. O.Paschereit article TerhaarKP2014 Journal of Engineering for Gas Turbines and Power 2014 137 4 041503 (10 pages) http://gasturbinespower.asmedigitalcollection.asme.org/data/Journals/JETPEZ/931032/gtp_137_04_041503.pdf 0742-4795 10.1115/1.4028392 S.Terhaar O.Krüger C. O.Paschereit article Terhaar2014 Journal of Engineering for Gas Turbines and Power 2014 136 7 http://www.scopus.com/inward/record.url?eid=2-s2.0-84894523472&partnerID=40&md5=e5e37c408d2911b049f5a071dbcfaed7 ASME 0742-4795 (online), 1528-8919 (print) 10.1115/1.4026530 S.Terhaar B.Ćosić C. O.Paschereit K.Oberleithner article Terhaar2014a Combustion Science and Technology 2014 186 889-911 AbstractHumidified gas turbines and steam-injected gas turbines are promising technologies to lower the emissions and increase the efficiency and fuel flexibility of gas turbines. In the current study, the influence of steam-dilution on swirl-stabilized methane and hydrogen-fired flames is experimentally investigated at Reynolds numbers in the range of 22,000 to 32,000. Velocity fields and flame positions were measured using high-speed particle image velocimetry and OH* chemiluminescence. An extension of the quantitative light sheet technique was employed to estimate the temperature fields. The combined results reveal strong changes in the flame position, the velocity field, and the temperature field with increasing rates of steam dilution. In particular, three different flow and flame patterns are encountered: At dry conditions, a V-shaped flame stabilizes in a broad inner recirculation zone with low local turbulent kinetic energy; at moderate steam content, the flame changes into a trumpet-like shape; and at very high rates of steam-dilution, the flame detaches and shows an annular shape. The associated coherent flow structures are extracted from the PIV data employing proper orthogonal decomposition. The isothermal flow is dominated by a helical instability arising near the combustor inlet. This structure is completely suppressed for the dry flame and reappears for the heavily steam-diluted detached flame with similar shape and frequency as for the isothermal case. The flow field of the trumpet-like flame at intermediate to high steam dilution rates features a helical instability of lower frequency that is located further downstream than in the isothermal and very wet case. A conceptional explanation is presented that relates the suppression of the helical instability to the specific encountered temperature fields and flame shapes. http://www.tandfonline.com/eprint/WaarDIijpj9TcDDGM7Xk/full 10.1080/00102202.2014.890597 S.Terhaar K.Oberleithner C. O.Paschereit article GokeSTRGKFGP2014 Journal of Engineering for Gas Turbines and Power 2014 139 091508 1-8 http://gasturbinespower.asmedigitalcollection.asme.org/article.aspx?articleid=1838118&resultClick=1 0742-4795 10.1115/1.4026942 S.Göke S.Schimek S.Terhaar T. G.Reichel K.Göckeler O.Krüger J.Fleck P.Griebel C. O.Paschereit article Kruger2014 Journal of Fluid Science and Technology 2014 9 3 1--12 10.1299/jfst.2014jfst0040 O.Krüger C.Duwig S.Terhaar C. O.Paschereit article Cosic2014 Combustion Science and Technology 2014 186 6 713--736 http://www.tandfonline.com/doi/pdf/10.1080/00102202.2013.876420 0010-2202 10.1080/00102202.2013.876420 B.Ćosić J. P.Moeck C. O.Paschereit article Goeckeler2013c Journal of Engineering for Gas Turbines and Power 2014 136 4 041505 (12 pages) 0742-4795 (online), 1528-8919 (print) 10.1115/1.4026000 K.Göckeler S.Terhaar C. O.Paschereit article Cosic2014aa Combustion and Flame 2014 162 4 1046–1062 in press 0010-2180 10.1016/j.combustflame.2014.09.025 B.Ćosić S.Terhaar J. P.Moeck C. O.Paschereit article Bobusch2014c Combustion Science and Technology 2014 186 10-11 1680-1689 Constant volume combustion (CVC) in gas turbines is a promising way to achieve a step change in the efficiency of such systems. The most widely investigated technique to implement CVC in gas turbine systems is pulsed detonation combustion (PDC). Unfortunately, the PDC is associated with several disadvantages, such as sharp pressure transitions, entropy generation due to shock waves, and exergy losses due to kinetic energy. This work proposes a new way to implement CVC in a gas turbine combustion system: shockless explosion combustion (SEC). This technique utilizes acoustic waves inside the combustor to fill and purge the combustion tube. The combustion itself is controlled via the ignition delay time of the fuel/air mixture. By adjusting the ignition delay in a way such that the entire fuel/air volume undergoes homogeneous auto-ignition, no shock waves occur. Accordingly, the losses associated with a detonation wave are not present in the proposed system. Instead, a smooth pressure rise is created due to the heat release of the homogeneous combustion. The current article explains the SEC process in detail, and presents the identified challenges. Solutions to these challenges and the numerical and experimental approach are presented subsequently alongside with first preliminary results of the numerical studies. 10.1080/00102202.2014.935624 B.Bobusch P.Berndt C. O.Paschereit R.Klein conference Wassmer2014 2014 http://www.efmc10.org/images/pdf/TIRSDAG_SAMLET_web.pdf 10th European Fluid Mechanics Conference (EFMC10), Technical University of Denmark (DTU Lyngby), Copenhagen, 14-18 September D.Wassmer B.Ćosić S.Terhaar C. O.Paschereit conference Wieser2014c 2014 1. Aerodynamic Workshop at Chalmers University, Göteborg, Schweden D.Wieser H.-J.Schmidt C. N.Nayeri C. O.Paschereit conference Nayeri2014g 2014 http://aerovehicles1.sciencesconf.org/conference/aerovehicles1/pages/2_Program_1.pdf First International Conference in Numerical and Experimental Aerodynamics of Road Vehicles and Trains (Aerovehicles 1), 23-25 June 2014, Bordeaux, France C. N.Nayeri R.Woszidlo T.Stumper H.-J.Schmidt C. O.Paschereit conference Wieser2014b 2014 11. Tagung: Fahrzeug-Aerodynamik, Juli 2014, Haus der Technik, München D.Wieser H.-J.Schmidt C. N.Nayeri C. O.Paschereit conference Paschereit2014f 2014 http://www.igcs-chennai.org 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 C. O.Paschereit conference Stathopoulos2014 2014 European Turbine Network ETN: The Future of Gas Turbine Technology, 7th IGTC, Brussels, Belgium, Oct. 14-15 P.Stathopoulos S.Terhaar S.Schimek C. O.Paschereit incollection Gray2015b 2014 176-181 International Conference on Pulsating and Continuous Detonations Roy, G. D. and Frolov, S. M. Torus Press Combustion and Detonation Series Transient Combustion and Detonation Phenomena:Fundamentals and Applications J.Gray J. P.Moeck C. O.Paschereit inproceedings Strangfeld2014a 2014 AIAA 7th AIAA Theoretical Fluid Mechanics Conference, 16-20 June, Atlanta, GA, USA 978-1-62410-293-6 0.2514/6.2014-2926 C.Strangfeld H.Mueller-Vahl D.Greenblatt C. N.Nayeri C. O.Paschereit inproceedings Kirk2014a 2014 ASME Paper GT2014-25926 V03BT46A019 (9 pages) http://proceedings.asmedigitalcollection.asme.org/data/Conferences/ASMEP/80912/V03BT46A019-GT2014-25926.pdf Proceedings of ASME Turbo Expo 2014, June 16-20, 2014, Düsseldorf, Germany 978-0-7918-4566-0 10.1115/GT2014-25926 W.Kirk V. R.Capece G.Pechlivanoglou C. N.Nayeri C. O.Paschereit inproceedings MuellerVahl2014 2014 AIAA 32nd AIAA Applied Aerodynamics Conference, 16-20 June, Atlanta, GA, USA 978-1-62410-288-2 10.2514/6.2014-2562 H.Mueller-Vahl C. N.Nayeri C. O.Paschereit D.Greenblatt inproceedings Matthew2014 2014 ASME Paper GT2014-27151 V03BT46A031 Proceedings of ASME Turbo Expo 2014, June 16-20, 2014, Düsseldorf, Germany 978-0-7918-4566-0 10.1115/GT2014-27151 L.Matthew D.Marten G.Pechlivanoglou C. N.Nayeri C. O.Paschereit inproceedings Niether2014a 2014 ASME Paper GT2014-25922 V03BT46A018 http://asmedigitalcollection.asme.org/data/Conferences/ASMEP/80912/V03BT46A018-GT2014-25922.pdf Proceedings of ASME Turbo Expo 2014, June 16-20, 2014, Düsseldorf, Germany 978-0-7918-4566-0 10.1115/GT2014-25922 S.Niether B.Bobusch D.Marten G.Pechlivanoglou C. N.Nayeri C. O.Paschereit inproceedings Reichel2014b 2014 Proceedings of the 8th International Seminar on Flame Structures 978-3-943685-96-1 T. G.Reichel C. O.Paschereit inproceedings Nayeri2014d 2014 43-51 Woodhead Publishing International Vehicle Aerodynamics Conference, 14-15 October, Loughboriugh, UK 978-0-08-100199-8 (print), 978-0-08-100245-2 (online) C. N.Nayeri D.Wieser H.-J.Schmidt C.Strangfeld C. O.Paschereit inproceedings TerhaarKP2014_2 2014 ASME Paper GT2014-27023 Proceedings of ASME Turbo Expo 2014, June 16-20, 2014, Düsseldorf, Germany S.Terhaar O.Krüger C. O.Paschereit inproceedings Nawroth2014 2014 AIAA paper no. 2014-2255 http://arc.aiaa.org/doi/abs/10.2514/6.2014-2255 11th AIAA/ASME Joint Thermophysics and Heat Transfer Conference, June 16-20, 2014, Atlanta, GA, USA 10.2514/6.2014-2255 H.Nawroth C. O.Paschereit inproceedings ReichelTP2014 2014 ASME Paper: GT2014-27002 Proceedings of ASME Turbo Expo 2014, June 16-20, 2014, Düsseldorf, Germany T. G.Reichel S.Terhaar C. O.Paschereit inproceedings Gockeler2014b 2014 ASME Paper GT2014-26811 V04BT04A042 (10 pages) Proceedings of ASME Turbo Expo 2014, June 16-20, 2014, Düsseldorf, Germany 978-0-7918-4569-1 10.1115/GT2014-26811 K.Katharina O.Krüger C. O.Paschereit inproceedings Kruger2014a 2014 c Wccm Xi 5217--5228 http://www.wccm-eccm-ecfd2014.org/admin/files/filePaper/p3072.pdf Onate, E. and Oliver, J. and Huerta, A. Proceedings of the 6th European Conference on Computational Fluid Dynamics, 20-25 July, Barcelona, Spain O.Krüger C.Schrödinger A.Lengwinat C. O.Paschereit inproceedings Ostermann2014a 2014 AIAA paper no. 2014-1142 http://arc.aiaa.org/doi/abs/10.2514/6.2014-1142 AIAA SciTech, 52nd Aerospace Sciences Meeting, January 13- 17, 2014, National Harbor, MD, USA 978-1-62410-256-1 10.2514/6.2014-1142 F.Ostermann R.Woszidlo S.Gärtlein C. N.Nayeri C. O.Paschereit inproceedings Kabiraj2014 2014 AIAA paper no. 2014-0623 http://arc.aiaa.org/doi/abs/10.2514/6.2014-0623 AIAA SciTech, 52nd Aerospace Sciences Meeting, January 13- 17, 2014, National Harbor, MD, USA 978-1-62410-256-1 10.2514/6.2014-0623 L.Kabiraj H.Nawroth A.Saurabh C. O.Paschereit inproceedings Wassmer2014 2014 American Institute of Aeronautics and Astronautics AIAA Aviation 0010-2202 10.2514/6.2014-3179 D.Wassmer B.Ćosić C. O.Paschereit inproceedings Saurabh2014a 2014 ASME Paper GT2014-26829 V04BT04A043 (9 pages) http://proceedings.asmedigitalcollection.asme.org/data/Conferences/ASMEP/80916/V04BT04A043-GT2014-26829.pdf Proceedings of ASME Turbo Expo 2014, June 16-20, 2014, Düsseldorf, Germany 978-0-7918-4569-1 10.1115/GT2014-26829 A.Saurabh R.Steinert J. P.Moeck C. O.Paschereit inproceedings Ostermann2014a 2014 AIAA paper no. 2014-1143 http://arc.aiaa.org/doi/abs/10.2514/6.2014-1143 AIAA SciTech, 52nd Aerospace Sciences Meeting, January 13- 17, 2014, National Harbor, MD, USA 978-1-62410-256-1 10.2514/6.2014-1143 S.Gärtlein R.Woszidlo F.Ostermann C. N.Nayeri C. O.Paschereit inproceedings Geiser2014a 2014 AIAA paper no. 2015-2476 AIAA Aviation, 13th AIAA/CEAS Aeroacoustics Conference, 16-20 June 2014, Atlanta, Georgia, USA 978-1-62410-285-1 10.2514/6.2014-2476 G.Geiser H.Nawroth A.Hosseinzadeh F.Zhang H.Bockhorn P.Habisreuther J.Janicka C. O.Paschereit W.Schroeder inproceedings Vahl2014 2014 2 35-40 http://dx.doi.org/10.1007/978-3-642-54696-9_6 Hölling, Michael and Peinke, Joachim and Ivanell, Stefan Springer Berlin Heidelberg Research Topics in Wind Energy Wind Energy - Impact of Turbulence English 978-3-642-54695-2 10.1007/978-3-642-54696-9_6 H.Mueller-Vahl C.Strangfeld C. N.Nayeri C. O.Paschereit D.Greenblatt inproceedings Pechlivanoglou2014a 2014 ASME Paper GT2014-25309 V03BT46A005 (9 pages) http://proceedings.asmedigitalcollection.asme.org/data/Conferences/ASMEP/80912/V03BT46A005-GT2014-25309.pdf Proceedings of ASME Turbo Expo 2014, June 16-20, 2014, Düsseldorf, Germany 978-0-7918-4566-0 10.1115/GT2014-25309 G.Pechlivanoglou G.Weinzierl I.Masmanidis C. N.Nayeri T.Philippidis C. O.Paschereit article Bobusch2013b Journal of Engineering for Gas Turbines and Power 2013 11 1 136 2 021506 0742-4795 (online), 1528-8919 (print) 10.1115/1.4025375 B.Bobusch B.Ćosić J. P.Moeck C. O.Paschereit article OberleithnerTRP2013 Journal of Engineering for Gas Turbines and Power 2013 9 23 135 12 121506 (9 Pages) 0742-4795 (online), 1528-8919 (print) 10.1115/1.4025130 K.Oberleithner S.Terhaar L.Rukes C. O.Paschereit article Krebs2013 Journal of Engineering for Gas Turbines and Power 2013 6 24 135 8 081503 (8 Pages) 0742-4795 (online), 1528-8919 (print) 10.1115/1.4023887 W.Krebs H.Krediet S.Hermeth T. E. P.Poinsot S.Schimek C. O.Paschereit article Marten2013c International Journal of Emerging Technology and Advanced Engineering (IJETAE) 2013 2 3 special issue 3 264-269 http://www.ijetae.com/files/Conference%20ICERTSD-2013/IJETAE_ICERTSD_0213_41.pdf 2250–2459 (Online) D.Marten J.Wendler G.Pechlivanoglou C. N.Nayeri C. O.Paschereit article Krueger2013 Journal of Engineering for Gas Turbines and Power 2013 1 3 135 2 021501 (10 pages) http://link.aip.org/link/?GTP/135/021501/1 ASME 0742-4795 (online), 1528-8919 (print) 10.1115/1.4007718 O.Krüger S.Terhaar C. O.Paschereit C.Duwig article LacosteMPL2013 Journal of Propulsion and Power 2013 29 3 748-751 American Institute of Aeronautics and Astronautics 0748-4658, EISSN: 1533-3876 10.2514/1.B34819 D. A.Lacoste J. P.Moeck C. O.Paschereit C. O.Laux article Albin2013b Fuel Processing Technology 2013 107 27--35 Global burning velocities of methane–air–steam mixtures are measured on prismatic laminar Bunsen flames and lifted turbulent V-flames for various preheating temperatures, equivalence ratios and steam mixture fractions at atmospheric pressure. Experiments are conducted on a new rectangular slot-burner. Experimental burning velocities are compared to computed flame speeds of one dimensional adiabatic premixed flames using detailed mechanisms (Konnov 0.5 and GRI Mech 3.0). Mean profiles of radicals OH* are also extracted from these flames and compared to simulation results. http://www.sciencedirect.com/science/article/pii/S0378382012002652 0378-3820 10.1016/j.fuproc.2012.06.027 E.Albin H.Nawroth S.Göke Y.D'Angelo C. O.Paschereit article Bobusch2013d Experiments in Fluids 2013 54 6 1-12 The internal flow characteristics of a fluidic oscillator were investigated experimentally. Particle image velocimetry and time-resolved pressure measurements were employed in water to visualize and quantify the internal flow patterns. The method of proper orthogonal decomposition was applied to random flow field snap shots for phase reconstruction of one oscillation cycle. The resulting phase-averaged information provides detailed insight into the oscillation mechanism as well as into the interaction between the main chamber of the oscillator and its feedback channels. A growing recirculation bubble between the main jet and the attachment wall is identified as an underlying mechanism that causes the main jet to oscillate. The flow field measurements are complemented by time-resolved pressure measurements at various internal locations which yield additional comprehension of the switching behavior and accompanying timescales. Geometrical features, in particular at the inlet and outlet of the mixing chamber, are found to have a crucial impact on important flow characteristics such as oscillation frequency and jet deflection. http://link.springer.com/content/pdf/10.1007%2Fs00348-013-1559-6.pdf Springer-Verlag 0723-4864 (print), 1432-1114 (online) 10.1007/s00348-013-1559-6 B.Bobusch R.Woszidlo J. M.Bergada C. N.Nayeri C. O.Paschereit article Goeke2012b Fuel Processing Technology 2013 107 14-22 http://www.sciencedirect.com/science/article/pii/S0378382012002408 Goeke_FuProc2012.pdf 0378-3820 10.1016/j.fuproc.2012.06.019 S.Göke M.Füri G.Bourque B.Bobusch K.Göckeler O.Krüger S.Schimek S.Terhaar C. O.Paschereit article zhang2013 Acta Acustica united with Acustica 2013 99 6 940-951 10.3813/AAA.918673 F.Zhang P.Habisreuther H.Bockhorn H.Nawroth C. O.Paschereit conference saurabh2013c 2013 Euromech Colloquium 546: Combustion Dynamics and Combustion Noise, May 13-16, 2013, Menaggio, Italy A.Saurabh C. O.Paschereit conference nawroth2013d 2013 Euromech Colloquium 546: Combustion Dynamics and Combustion Noise, May 13-16, 2013, Menaggio, Italy H.Nawroth J. P.Moeck C. O.Paschereit conference Gray2013c 2013 #193 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) J.Gray J. P.Moeck C. O.Paschereit conference nawroth2013e 2013 Euromech Colloquium 546: Combustion Dynamics and Combustion Noise, May 13-16, 2013, Menaggio, Italy A.Hosseinzadeh H.Nawroth J.Janicka C. O.Paschereit conference nawroth2013f 2013 Euromech Colloquium 546: Combustion Dynamics and Combustion Noise, May 13-16, 2013, Menaggio, Italy G.Geiser A.Hosseinzadeh H.Nawroth F.Zhang J.Schröder J.Janicka C. O.Paschereit P.Habisreuther H.Bockhorn conference Bobusch2013e 2013 #181 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) B.Bobusch P.Berndt C. O.Paschereit R.Klein conference saurabh2013e 2013 3rd International Symposium on Bifurcations and Instabilities in Fluid Dynamics (BIFD 2013), July 8-11, 2013, Technion, Haifa, Israel A.Saurabh C. O.Paschereit inproceedings PaschereitTOo2013 2013 Proceedings of 4th International Conference on Jets, Wakes and Separated Flows (ICJWSF), Sep 17-21, 2013, Nagoya, Aichi, Japan 978-4-88898-234-4 (CD) C. O.Paschereit S.Terhaar K.Oberleithner B.Ćosić inproceedings Gockeler2013 2013 1--6 Japan Society of Mechanical Engineers

Nagoya

Proceedings of 4th International Conference on Jets, Wakes and Separated Flows (ICJWSF), Sep 17-21, 2013, Nagoya, Aichi, Japan 978-4-88898-234-4 (CD) K.Göckeler E.Albin O.Krüger C. O.Paschereit inproceedings kabiraj2013b 2013 P4-60 6 pages Proceedings of the 6th European Combustion Meeting (ECM), June 25-28, 2013, Lund, Sweden 978-91-637-2151-9 L.Kabiraj H.Nawroth A.Saurabh C. O.Paschereit inproceedings saurabh2013a 2013 Volume 1B: Combustion, Fuels and Emissions ASME paper GT2013-95732 V01BT04A057 http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=1775958 Proc. ASME Turbo Expo 2013, June 3-7, San Antonio, Texas, USA 978-0-7918-5511-9 10.1115/GT2013-95732 A.Saurabh C. O.Paschereit inproceedings MoeckLLP2013 2013 AIAA paper no. 2013-0565 http://arc.aiaa.org/doi/pdfplus/10.2514/6.2013-565 51st AIAA Aerospace Science Meeting, Grapevine, Texas, USA, Jan. 07-10 10.2514/6.2013-565 J. P.Moeck D. A.Lacoste C. O.Laux C. O.Paschereit inproceedings Marten2013b 2013 ASME paper GT2013-94979 V008T44A017 (9 pages) Proc. ASME Turbo Expo 2013, June 3-7, San Antonio, Texas, USA 978-0-7918-5529-4 10.1115/GT2013-94979 D.Marten J.Wendler G.Pechlivanoglou C. N.Nayeri C. O.Paschereit inproceedings saurabh2013b 2013 P1-24 Proceedings of the 6th European Combustion Meeting (ECM), June 25-28, 2013, Lund, Sweden 978-91-637-2151-9 A.Saurabh C. O.Paschereit inproceedings Schimek2013 2013 AIAA paper no. 2013-0693 http://arc.aiaa.org/doi/pdfplus/10.2514/6.2013-693 51st AIAA Aerospace Science Meeting, Grapevine, Texas, USA, Jan. 07-10 10.2514/6.2013-693 S.Schimek S.Göke C. O.Paschereit inproceedings Nayeri2013a 2013 44 9-27 Interdisziplinärer Forschungsverbund (IFV) Bahntechnik e.V., Salzufer 17-19, 10587 Berlin, Germany Bahntechnik aktuell, Schriftenreihe des Interdisziplinären Forschungsverbundes Bahntechnik e.V. 2nd international symposium on Rail Aerodynamics, Aerodynamics of Trains and Infrastructure, Berlin, Germany 978-3-940727-37-4 1867-240X C. N.Nayeri U.Gencaslan A.Tietze C.Strangfeld M.Sieber D.Wieser M.Weise C. O.Paschereit inproceedings nawroth2013b 2013 AIAA paper 2013-2601 American Institute of Aeronautics and Astronautics 43rd AIAA Fluid Dynamics Conference, June 24-27, 2013, San Diego, California, USA 978-1-62410-214-1 10.2514/6.2013-2601 H.Nawroth K.Moriarty J.Beuth C. O.Paschereit inproceedings Schroedinger2013d 2013 paper no. P3-65 Proceedings of the 6th European Combustion Meeting (ECM) June 25-28, 2013, Lund, Sweden 978-91-637-2151-9 C.Schrödinger D.Nolte M.Oevermann C. O.Paschereit inproceedings Strangfeld2013a 2013 SAE Technical Paper 2013-01-1251 The realistic car model DrivAer is investigated experimentally up to a Reynolds number of 2.8 million in the closed-loop wind tunnel at the “Technische Universität” Berlin. This new open-source design-hybrid of an “Audi A4™” and a “BMW 3 series™” possesses more representative car features as the well-known generic “Ahmed-Body”. Therefore, the study of realistic flow structures is enabled. The main focus of the experimental investigations is the analysis of unsteady flow phenomena in the near wake of the model with a fastback configuration. An internal six component force balance and 63 pressure sensors measured simultaneously the forces and surface pressures with a sample rate of 5kHz. Furthermore, the velocity field in the plane of symmetry is visualized through Particle Image Velocimetry. In the trailing edge region of the roof and the beginning of the rear window a local low pressure peak likely caused by a vortex is detected. This vortex may sustain the flow attachment downstream and hence, improves the pressure recovery. Although instantaneous flow field snapshots illustrate large-scale structures and the meandering of a free stagnation point in the model's wake, no dominant frequencies are found from spectral analysis of time-resolved pressure and force measurements. http://papers.sae.org/2013-01-1251/ Society of Automobile Engineers SAE 2013 World Congress & Exhibition, 16. April 2013, Detroit, Michigan, USA 10.4271/2013-01-1251 C.Strangfeld D.Wieser H.-J.Schmidt R.Woszidlo C. N.Nayeri C. O.Paschereit inproceedings kabiraj2013a 2013 AIAA paper 2013-2002 http://arc.aiaa.org/doi/pdf/10.2514/6.2013-2002 American Institute of Aeronautics and Astronautics 19th AIAA/CEAS Aero-acoustics Conference, May 27-29, 2013, Berlin, Germany 10.2514/6.2013-2002 L.Kabiraj H.Nawroth A.Saurabh C. O.Paschereit inproceedings Reichel2013e 2013 36.1-36.7 Kähler, C. and Hain, R. and Cierpka, C. and Ruck, B. and Leder, A. and Dopheide, D. Proceedings der 21. GALA-Fachtagung "Lasermethoden in der Strömungsmesstechnik", 3.-5. September 2013, Universität der Bundeswehr, München, Germany 978-3-9805613-9-6 2194-2447 T. G.Reichel C. O.Paschereit inproceedings Reichel2013d 2013 AIAA paper no. 2013-2603 http://arc.aiaa.org/doi/pdfplus/10.2514/6.2013-2603 51st AIAA Aerospace Science Meeting, Grapevine, Texas, USA, Jan. 07-10 10.2514/6.2013-2603 T. G.Reichel S.Terhaar C. O.Paschereit inproceedings nawroth2013c 2013 AIAA paper 2013-2459 American Institute of Aeronautics and Astronautics 43rd AIAA Fluid Dynamics Conference, June 24-27, 2013, San Diego, California, USA 978-1-62410-214-1 10.2514/6.2013-2459 H.Nawroth C. O.Paschereit F.Zhang P.Habisreuther H.Bockhorn inproceedings Terhaar2013 2013 ASME paper GT2013-95729 V01BT04A056 (13 pages) Proc. ASME Turbo Expo 2013, June 3-7, San Antonio, Texas, USA 978-0-7918-5511-9 10.1115/GT2013-95729 S.Terhaar B.Ćosić K.Oberleithner C. O.Paschereit inproceedings Holst2013 2013 ASME paper GT2013-94381 V008T44A011 (10 pages) Proc. ASME Turbo Expo 2013, June 3-7, San Antonio, Texas, USA 978-0-7918-5529-4 10.1115/GT2013-94381 D.Holst A.Bach C. N.Nayeri C. O.Paschereit inproceedings Cosic2012d 2013 ASME paper GT2013-94782 V01AT04A056 (11 pages) Proc. ASME Turbo Expo 2013, June 3-7, San Antonio, Texas, USA 978-0-7918-5510-2 10.1115/GT2013-94782 S.Göke S.Schimek S.Terhaar T. G.Reichel K.Göckeler O.Krüger J.Fleck P.Griebel C. O.Paschereit inproceedings kabiraj2013c 2013 P2-30 6 pages Proceedings of the 6th European Combustion Meeting (ECM), June 25-28, 2013, Lund, Sweden 978-91-637-2151-9 L.Kabiraj A.Saurabh R.Steinert C. O.Paschereit inproceedings Kruger2013a 2013 1--6 Japan Society of Mechanical Engineers Proceedings of 4th International Conference on Jets, Wakes and Separated Flows (ICJWSF), Sep 17-21, 2013, Nagoya, Aichi, Japan 978-4-88898-234-4 (CD) O.Krüger C.Duwig S.Terhaar C. O.Paschereit inproceedings Kruger2013b 2013 AIAA paper 2013-2953 1--16 http://arc.aiaa.org/doi/abs/10.2514/6.2013-2953 American Institute of Aeronautics and Astronautics 21th AIAA Computational Fluid Dynamics Conference, June 24-27, 2013, San Diego, California, USA 10.2514/6.2013-2953 O.Krüger C.Duwig S.Terhaar C. O.Paschereit inproceedings Schroedinger2013c 2013 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) C.Schrödinger M.Oevermann C. O.Paschereit inproceedings Bobusch2013b 2013 AIAA paper 2013-2953 1--15 a parametric study of,active flow control actuator,cfd,flow control actuators,fludic oscillator,fluid dynamics,fluidic oscillators are gaining,interest as novel active,modeling and simulation,numerical model to perform,parameter study,subject,the current,the internal,work utilizes a validated http://arc.aiaa.org/doi/abs/10.2514/6.2013-2709 American Institute of Aeronautics and Astronautics 21th AIAA Computational Fluid Dynamics Conference, June 24-27, 2013, San Diego, California, USA 10.2514/6.2013-2709 B.Bobusch R.Woszidlo O.Krüger C. O.Paschereit inproceedings Kruger2013 2013 AIAA paper 2013-3087 1--13 http://arc.aiaa.org/doi/abs/10.2514/6.2013-3087 American Institute of Aeronautics and Astronautics 21th AIAA Computational Fluid Dynamics Conference, June 24-27, 2013, San Diego, California, USA 10.2514/6.2013-3087 O.Krüger B.Bobusch R.Woszidlo C. O.Paschereit inproceedings Bobusch2013c 2013 ASME paper GT2013-95649 V01BT04A048 (12 pages) Proc. ASME Turbo Expo 2013, June 3-7, San Antonio, Texas, USA 978-0-7918-5511-9 10.1115/GT2013-95649 B.Bobusch B.Ćosić J. P.Moeck C. O.Paschereit inproceedings Cosic2013e 2013 ASME paper GT2013-94160 V01AT04A007 (11 pages) Proc. ASME Turbo Expo 2013, June 3-7, San Antonio, Texas, USA 978-0-7918-5510-2 10.1115/GT2013-94160 B.Ćosić J. P.Moeck C. O.Paschereit inproceedings Marten2013 International Journal of Emerging Technology and Advanced Engineering, vol. 3, special issue 3 2013 http://www.ijetae.com/files/Conference%20ICERTSD-2013/IJETAE_ICERTSD_0213_41.pdf International Conference on Energy Resources and Technologies for Sustainable Development (ICERTSD), Bengal Engineering & Science University, Shibpur, Howrah, West Bengal, INDIA ISSN 2250 – 2459 (Online) D.Marten J.Wendler G.Pechlivanoglou C. N.Nayeri C. O.Paschereit inproceedings Goeckeler2013a 2013 Volume 1B: Combustion, Fuels and Emissions ASME paper GT2013-95594 V01BT04A047 (12 pages) Proc. ASME Turbo Expo 2013, June 3-7, San Antonio, Texas, USA 978-0-7918-5511-9 10.1115/GT2013-95594 K.Göckeler S.Terhaar C. O.Paschereit inproceedings saurabh2013d 2013 1--6 Proceedings of 4th International Conference on Jets, Wakes and Separated Flows (ICJWSF), Sep 17-21, 2013, Nagoya, Aichi, Japan 978-4-88898-234-4 (CD) A.Saurabh C. O.Paschereit inproceedings Vahl2013 2013 AIAA paper no. 2013-0854 http://arc.aiaa.org/doi/pdfplus/10.2514/6.2013-693 51st AIAA Aerospace Science Meeting, Grapevine, Texas, USA, Jan. 07-10 10.2514/6.2013-854 H.Mueller-Vahl C.Strangfeld C. N.Nayeri C. O.Paschereit D.Greenblatt inproceedings Bach2013 2013 ASME paper GT2013-94369 V008T44A010 (8 pages) Proc. ASME Turbo Expo 2013, June 3-7, San Antonio, Texas, USA 978-0-7918-5529-4 10.1115/GT2013-94369 A.Bach D.Holst C. N.Nayeri C. O.Paschereit inproceedings TerhaarBP2013 2013 37.1-37.8 Kähler, C. and Hain, R. and Cierpka, C. and Ruck, B. and Leder, A. and Dopheide, D. Proceedings der 21. GALA-Fachtagung "Lasermethoden in der Strömungsmesstechnik", 3.-5. September 2013, Universität der Bundeswehr, München, Germany 978-3-9805613-9-6 (print) 2194-2447 S.Terhaar J.Beuth C. O.Paschereit inproceedings Terhaar2013a 2013 1--16 http://arc.aiaa.org/doi/pdfplus/10.2514/6.2013-2602 Proceedings of 43st AIAA Fluid Dynamics Conference and Exhibit, June 24-27 2013, San Diego, CA, USA 10.2514/6.2013-2602 S.Terhaar T. G.Reichel C.Schrödinger L.Rukes K.Oberleithner C. O.Paschereit inproceedings Oberleithner2013 2013 ASME paper GT2013-95509 V01BT04A041 (12 pages) Proc. ASME Turbo Expo 2013, June 3-7, San Antonio, Texas, USA 978-0-7918-5511-9 10.1115/GT2013-95509 K.Oberleithner S.Terhaar L.Rukes C. O.Paschereit inproceedings Nayeri2013c 2013 1--6 nayeri_ICJWSF_2013.pdf Japan Society of Mechanical Engineers Proceedings of 4th International Conference on Jets, Wakes and Separated Flows (ICJWSF), Sep 17-21, 2013, Nagoya, Aichi, Japan 978-4-88898-234-4 (CD) C. N.Nayeri U.Neumann J.Tschepe C.Strangfeld D.Wieser C. O.Paschereit article TerhaarBP2012_2 Journal of Engineering for Gas Turbines and Power 2012 9 20 134 11 111501 0742-4795 (online), 1528-8919 (print) 10.1115/1.4007165 S.Terhaar B.Bobusch C. O.Paschereit article Cosic2012c Journal of Engineering for Gas Turbines and Power 2012 8 22 134 10 101503 http://link.aip.org/link/?GTP/134/101503/1 ASME 0742-4795 (online), 1528-8919 (print) 10.1115/1.4007024 B.Ćosić T. G.Reichel C. O.Paschereit article Krediet2012a Combustion Science and Technology 2012 7 184 7-8 888--900 Thermo-acoustic characterization of gas turbine combustion systems is crucial for a successful development of new gas turbine engines to meet emission and efficiency targets. In this context, it becomes more and more necessary to predict the limit cycle amplitudes of thermo-acoustic induced combustion instabilities in order to figure out if they can be tolerated or if they are above the critical design limit and will cause damage to the engine. For the prediction of limit cycle amplitudes, the nonlinear flame response of the combustion system is needed, which is represented in this work by the flame describing function (FDF). In this article, the identification of the FDF from a large eddy simulation (LES) is validated. The test case used was a premixed atmospheric swirl flame, for which experimental data on the FDF were available. First a steady reacting LES solution was obtained and compared to experimental data. The simulation was then excited by superimposing a mono-frequency harmonic wave on the velocity inlet boundary condition. Both the frequency and amplitude of the acoustic wave were varied to obtain the FDF. The calculated FDF was in good agreement with experimental data. At a frequency of 115 Hz, the heat release rate of the flame was found to saturate for larger excitation amplitudes. http://www.mendeley.com/research/identification-flame-describing-function-premixed-swirl-flame-les/ 0010-2202 10.1080/00102202.2012.663981 H. J.Krediet C. H.Beck W.Krebs S.Schimek C. O.Paschereit J. B. W.Kok article cosic:2012 Journal of Engineering for Gas Turbines and Power 2012 4 12 134 6 061502 http://link.aip.org/link/?GTP/134/061502/1 ASME 0742-4795 (online), 1528-8919 (print) 10.1115/1.4005986 B.Ćosić B.Bobusch J. P.Moeck C. O.Paschereit article Gelbert2012 Journal of Process Control 2012 22 4 700-709 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. http://www.sciencedirect.com/science/article/pii/S0959152412000340 0959-1524 10.1016/j.jprocont.2012.01.022 G.Gelbert J. P.Moeck C. O.Paschereit R.King article Winkler2012 AIAA Journal 2012 50 7 1614--1620 10.2514/1.J051578 M.Winkler K.Becker C.Doolan F.Kameier C. O.Paschereit article Gelbert2012a Control Engineering Practice 2012 20 8 770-782 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. http://www.sciencedirect.com/science/article/pii/S0967066112000809 0967-0661 10.1016/j.conengprac.2012.03.016 G.Gelbert J. P.Moeck C. O.Paschereit R.King article Oberleithner2012a AIAA Journal 2012 50 7 1437-1452 10.2514/1.J050642 K.Oberleithner R.Seele C. O.Paschereit I.Wygnanski article lacarelle2012 Journal of Engineering for Gas Turbines and Power 2012 134 2 021503 (7 pages) Jets in crossflow are widely used in the industry for homogenization or cooling tasks.Recently, pulsating jets have been investigated as a mean to increase the scalar mixingefficiency of such configurations, whether for a single jet or for an array of jets. To avoidthe disadvantages of mechanically actuated flows (costs, maintenance), a new injectorbased on a fluidics oscillator has been designed. Four injectors have been implementedin a generical jet in crossflow configuration and the mixing efficiency of the setup wascompared with the one of the same setup equiped with standard non oscillating jets. Withhelp of high-speed concentration measurement technique, the scalar mixing quality ofboth setups was measured at three positions downstream of the injection plane. In all thecases tested, the fluidics injectors present a better temporal homogenization, characterized by the Danckwerts unmixedness criterion, than the standard jets. For a defined mixing quality, a decrease of the mixing length by approximately 50% can be achieved with the fluidics injectors. Furthermore, the new injectors exhibit a mixing quality which isless sensitive to variations of the jet to crossflow momentum. The flapping motion of thefluidics injectors induces a wider azimuthal spreading of the fluidics jets immediatelydownstream of the injection location. This increases the macro- and micro-mixing phenomea which lead then to the high gains in mixing quality. It is thus demonstrated that fluidics oscillators present a strong potential to improve the passive scalar homogenization of jet in crossflow configurations. http://link.aip.org/link/?GTP/134/021503/1 ASME 0742-4795 (online), 1528-8919 (print) 10.1115/1.4004373 A.Lacarelle C. O.Paschereit article Goeke2012d Journal of Propulsion and Power 2012 American Institute of Aeronautics and Astronautics 0748-4658, EISSN: 1533-3876 10.2514/1.B34577 S.Göke C. O.Paschereit article Moeck2012 International journal of spray and combustion dynamics 2012 4 1 1-28 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. Multi-Science Publishing 1756-8277 J. P.Moeck C. O.Paschereit article Candel2012 Comptes Rendus Mécanique 2012 340 11--12 758--768 http://www.sciencedirect.com/science/article/pii/S163107211200188X 1631-0721 10.1016/j.crme.2012.10.024 S.Candel D.Durox T. S.Schuller P.Palies J.-F.Bourgouin J. P.Moeck article Schneider:2012 tm - Technisches Messen 2012 79 6 304--309 http://www.oldenbourg-link.com/doi/abs/10.1524/teme.2012.0211 Oldenbourg Wissenschaftsverlag GmbH 0171-8096 10.1524/teme.2012.0211 T.Schneider L.Goubergrits C. O.Paschereit U.Kertzscher K.Affeld conference Pechlivanoglou2012 2012 Conference on Modelling Fluid Flow, The 15th International Conference on Fluid Flow Technologies, Budapest, Hungary, 4-7 Sep. G.Pechlivanoglou C. N.Nayeri C. O.Paschereit conference Sieber2012 2012 http://www.efmc9.eu/absbook/files/0519_SH3_Sieber_Moritz.pdf 9th European Fluid Mechanics Conference, University of Rome "Tor Vergata", Italy, 9-13 September M.Sieber L.Rukes K.Oberleithner C. N.Nayeri C. O.Paschereit conference Wendler2012 2012 QBlade_poster.pdf Renewable Energy 2030 - Experts Visions, Carl von Ossietzky University, Oldenburg, Germany, 1-2 Oct. J.Wendler D.Marten G.Pechlivanoglou C. N.Nayeri C. O.Paschereit conference Rukes2012 2012 http://www.efmc9.eu/absbook/files/0242_IN11_Rukes_Lothar.pdf 9th European Fluid Mechanics Conference, University of Rome "Tor Vergata", Italy, 9-13 September L.Rukes K.Oberleithner M.Sieber C. N.Nayeri C. O.Paschereit conference Vahl2012b 2012 EUROMECH Colloquium 528 - Wind Energy and the impact of turbulence on the conversion process, Oldenburg, Germany, 22-24 Feb. H.Mueller-Vahl C.Strangfeld C. N.Nayeri C. O.Paschereit D.Greenblatt inproceedings Cosic2012b 2012 ASME paper GT2012-69033 767-779 (13 pages) Proc. ASME Turbo Expo 2012, June 11-15, Bella Center, Copenhagen, Denmark 978-0-7918-4468-7 10.1115/GT2012-69033 B.Ćosić T. G.Reichel C. O.Paschereit inproceedings Schimek2012c 2012 ASME paper GT2012-69785 1321-1333 (13 pages) Proc. ASME Turbo Expo 2012, June 11-15, Bella Center, Copenhagen, Denmark 978-0-7918-4468-7 10.1115/GT2012-69785 S.Schimek B.Ćosić J. P.Moeck S.Terhaar C. O.Paschereit inproceedings schimek2012 2012 AIAA paper no. 2012-0932 http://arc.aiaa.org/doi/pdfplus/10.2514/6.2012-932 50th AIAA Aerospace Science Meeting, Nashville, Tennessee, USA, Jan. 9-12 10.2514/6.2012-932 S.Schimek S.Göke C.Schrödinger C. O.Paschereit inproceedings Krebs2012 2012 ASME paper GT2012-69477 1113-1124 (12 pages) Proc. ASME Turbo Expo 2012, June 11-15, Bella Center, Copenhagen, Denmark 978-0-7918-4468-7 10.1115/GT2012-69477 W.Krebs H.Krediet S.Hermeth T. E. P.Poinsot S.Schimek C. O.Paschereit inproceedings TerhaarBP2012 2012 1295-1306 (12 pages) Proc. ASME Turbo Expo 2012, June 11-15, Bella Center, Copenhagen, Denmark , ASME paper GT2012-69753 978-0-7918-4468-7 10.1115/GT2012-69753 S.Terhaar B.Bobusch C. O.Paschereit inproceedings nawroth2012a 2012 AIAA paper 2012-3072 http://arc.aiaa.org/doi/abs/10.2514/6.2012-3072 American Institute of Aeronautics and Astronautics 42nd AIAA Fluid Dynamics Conference, June 25-28, 2012, New Orleans, Louisiana, USA 10.2514/6.2012-3072 H.Nawroth A.Saurabh C. O.Paschereit F.Zhang P.Habisreuther H.Bockhorn inproceedings Schimek2012b 2012 ASME paper GT2012-69788 1335-1344 (10 pages) Proc. ASME Turbo Expo 2012, June 11-15, Bella Center, Copenhagen, Denmark 978-0-7918-4468-7 10.1115/GT2012-69788 S.Schimek S.Göke C.Schrödinger C. O.Paschereit inproceedings TerhaarP2012 2012 http://ltces.dem.ist.utl.pt/lxlaser/lxlaser2012/upload/212_paper_bysdxt.pdf 16th Int Symp on Applications of Laser Techniques to Fluid Mechanics Lisbon, Portugal, 09-12 July, 2012 S.Terhaar C. O.Paschereit inproceedings Goeke2012 2012 AIAA paper no. 2012-1272 http://arc.aiaa.org/doi/pdfplus/10.2514/6.2012-1272 50th AIAA Aerospace Science Meeting, Nashville, Tennessee, USA, Jan. 9-12 10.2514/6.2012-1272 S.Göke C. O.Paschereit inproceedings Goeke2012a 2012 The Eleventh International Conference on Combustion and Energy Utilization (11th ICCEU) S.Göke M.Füri G.Bourque K.Göckeler O.Krüger B.Bobusch S.Schimek S.Terhaar C. O.Paschereit inproceedings Kruger2012 2012 ASME paper GT2012-69446 1081-1094 (14 pages) Proc. ASME Turbo Expo 2012, June 11-15, Bella Center, Copenhagen, Denmark 978-0-7918-4468-7 10.1115/GT2012-69446 O.Krüger C.Duwig S.Terhaar C. O.Paschereit inproceedings Albin2012 2012 The Eleventh International Conference on Combustion and Energy Utilization (11th ICCEU) E.Albin H.Nawroth S.Göke Y.D'Angelo C. O.Paschereit inproceedings Schuller2012 2012 AIAA paper no. 2012-0985 http://arc.aiaa.org/doi/pdfplus/10.2514/6.2012-985 50th AIAA Aerospace Science Meeting, Nashville, Tennessee, USA, Jan. 9-12 10.2514/6.2012-985 T. S.Schuller A.Cuquel P.Palies J. P.Moeck D.Durox S.Candel inproceedings Schroedinger2012 2012 http://www.iccfd.org/iccfd7/assets/pdf/papers/ICCFD7-3401_paper.pdf Seventh International Conference on Computational Fluid Dynamics (ICCFD7), Big Island, Hawaii, July 9-13 C.Schrödinger C. O.Paschereit M.Oevermann inproceedings Schroedinger2012b 2012 ASME paper GT2012-69843 1345--1356 (12 pages) Proc. ASME Turbo Expo 2012, June 11-15, Bella Center, Copenhagen, Denmark 978-0-7918-4468-7 10.1115/GT2012-69843 C.Schrödinger J. P.Moeck M.Oevermann C. O.Paschereit inproceedings Vey2012 2012 AIAA paper no. 2012-317 http://arc.aiaa.org/doi/pdfplus/10.2514/6.2012-317 50th AIAA Aerospace Science Meeting, Nashville, Tennessee, USA, Jan. 9-12 10.2514/6.2012-317 S.Vey C. N.Nayeri C. O.Paschereit D.Greenblatt inproceedings Oberleithner2012 2012 ASME paper GT2012-69774 1307-1320 (14 pages) Proc. ASME Turbo Expo 2012, June 11-15, Bella Center, Copenhagen, Denmark 978-0-7918-4468-7 10.1115/GT2012-69774 K.Oberleithner S.Schimek C. O.Paschereit inproceedings Weinzierl2012 2012 ASME paper GT2012-69200 915-927 (13 pages) Proc. ASME Turbo Expo 2012, June 11-15, Bella Center, Copenhagen, Denmark 978-0-7918-4472-4 10.1115/GT2012-69200 G.Weinzierl G.Pechlivanoglou C. N.Nayeri C. O.Paschereit inproceedings Bobusch2012 2012 ASME paper GT2012-69034 781-794 (14 pages) Proc. ASME Turbo Expo 2012, June 11-15, Bella Center, Copenhagen, Denmark 978-0-7918-4468-7 10.1115/GT2012-69034 B.Bobusch J. P.Moeck S.Sadig C. O.Paschereit inproceedings Goeke2012c 2012 Paper ID Number: 17 Goeke2012c.pdf European Turbine Network ETN: The Future of Gas Turbine Technology, 6th IGTC, Brussels, Belgium, Oct. 17-18 S.Göke E.Albin K.Göckeler O.Krüger S.Schimek S.Terhaar C. O.Paschereit inproceedings Krueger2012 2012 http://www.iccfd.org/iccfd7/assets/pdf/papers/ICCFD7-3403_paper.pdf Seventh International Conference on Computational Fluid Dynamics (ICCFD7), Big Island, Hawaii, July 9-13 O.Krüger C.Duwig S.Terhaar C. O.Paschereit inproceedings Vahl2012 2012 ASME paper GT2012-69197 899-914 (16 pages) Proc. ASME Turbo Expo 2012, June 11-15, Bella Center, Copenhagen, Denmark 978-0-7918-4472-4 10.1115/GT2012-69197 H.Mueller-Vahl G.Pechlivanoglou C. N.Nayeri C. O.Paschereit article schimek2011 Journal of Engineering for Gas Turbines and Power 2011 4 25 133 10 101502 (7 pages) 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. http://link.aip.org/link/?GTP/133/101502/1 ASME 0742-4795 (online), 1528-8919 (print) 10.1115/1.4002946 S.Schimek J. P.Moeck C. O.Paschereit article Goeke2011c VGB PowerTech 2011 10 44--49 1435-3199 (print) S.Göke C. O.Paschereit article Petz2011 Physics of Fluids 2011 23 9 091102 bifurcation; confined flow; flow visualisation; fluid oscillations; jets; nozzles; shear turbulence; vortices; AIP 1070-6631 (print), 1089-7666 (online) 10.1063/1.3640007 C.Petz H. C.Hege K.Oberleithner M.Sieber C. N.Nayeri C. O.Paschereit I.Wygnanski B. R.Noack article Oberleithner2011c Pflügers Archiv European Journal of Physiology 2011 462 4 519-528 Sodium overload stiffens vascular endothelial cells in vitro and promotes arterial hypertension in vivo. The hypothesis was tested that the endothelial glycocalyx (eGC), a mesh of anionic biopolymers covering the surface of the endothelium, participates in the stiffening process. By using a mechanical nanosensor, mounted on an atomic force microscope, height (400 nm) and stiffness (0.25 pN/nm) of the eGC on the luminal endothelial surface of split-open human umbilical arteries were quantified. In presence of aldosterone, the increase of extracellular sodium concentration from 135 to 150 mM over 5 days (sodium overload) led the eGC shrink by 50% and stiffening by 130%. Quantitative eGC analyses reveal that sodium overload caused a reduction of heparan sulphate residues by 68% which lead to destabilization and collapse of the eGC. Sodium overload transformed the endothelial cells from a sodium release into a sodium-absorbing state. Spironolactone, a specific aldosterone antagonist, prevented these changes. We conclude that the endothelial glycocalyx serves as an effective buffer barrier for sodium. Damaged eGC facilitates sodium entry into the endothelial cells. This could explain endothelial dysfunction and arterial hypertension observed in sodium abuse. Institute of Physiology II, University of Münster, Robert-Koch-Str. 27b, 48149 Münster, Germany Biomedizin & Life Sciences Springer Berlin / Heidelberg 0031-6768 10.1007/s00424-011-0999-1 H.Oberleithner W.Peters K.Kusche-Vihrog S.Korte H.Schillers K.Kliche K.Oberleithner article Oberleithner2011a Journal of Fluid Mechanics 2011 679 383-414 The spatio-temporal evolution of a turbulent swirling jet undergoing vortex breakdown has been investigated. Experiments suggest the existence of a self-excited global mode having a single dominant frequency. This oscillatory mode is shown to be absolutely unstable and leads to a rotating counter-winding helical structure that is located at the periphery of the recirculation zone. The resulting time-periodic 3D velocity field is predicted theoretically as being the most unstable mode determined by parabolized stability analysis employing the mean flow data from experiments. The 3D oscillatory flow is constructed from uncorrelated 2D snapshots of particle image velocimetry data, using proper orthogonal decomposition, a phase-averaging technique and an azimuthal symmetry associated with helical structures. Stability-derived modes and empirically derived modes correspond remarkably well, yielding prototypical coherent structures that dominate the investigated flow region. The proposed method of constructing 3D time-periodic velocity fields from uncorrelated 2D data is applicable to a large class of turbulent shear flows. Available on CJO http://journals.cambridge.org/article_S0022112011001418 10.1017/jfm.2011.141 K.Oberleithner M.Sieber C. N.Nayeri C. O.Paschereit C.Petz H. C.Hege B. R.Noack I.Wygnanski conference Rukes2011 2011 EUROMECH Colloquium 525 - Instabilities and transition in three-dimensional flows with rotation, 21–-23 June 2011, École centrale de Lyon, France L.Rukes K.Oberleithner C. O.Paschereit conference Oberleithner2011d 2011 9th ERCOFTAC SIG 33 Workshop, Progress in Transition Modeling and Control K.Oberleithner C. O.Paschereit inproceedings Schimek2011b 2011 9 http://www.combustion-institute.it/proceedings/MCS-7/papers/PEC/PEC-05.pdf Proceedings of 7th Mediterranean Combustion Symposium (MCS), Chia Laguna, Cagliari, Sardinia, Italy, September 978-88-88104-12-6 (CD-ROM) H. J.Krediet C. H.Beck W.Krebs S.Schimek C. O.Paschereit inproceedings Strangfeld2011b 2011 36.1--36.9 Proceedings der 19. GALA-Fachtagung "Lasermethoden in der Strömungsmesstechnik", 2011, Ilmenau, Germany 978-3-9805613-7-2 (print) C.Strangfeld K.Göckeler S.Terhaar C. O.Paschereit inproceedings Goeke2011 2011 ASME paper GT2011-45696 Proc. ASME Turbo Expo 2011: Advancing Clean and Efficient Turbine Technology (GT2011), June 6-10, Vancouver, BC, Canada S.Göke S.Terhaar S.Schimek K.Göckeler C. O.Paschereit inproceedings Eisele2011 2011 Conventional wind turbine rotor blades are exposed to unsteady aerodynamic loads caused by wind gusts. Typically, the wind gusts have a duration of 1s to 10min, whereby maximum wind gusts with speeds 1.7 times faster than the hourly mean wind speed can occur [1]. These dynamic loads lead to undesired responses of the blade flap and chord-wise oscillations. The lifetime of a blade is significantly reduced by fatigue due to this effect. Furthermore, the tower is adversely affected by the resulting rotor dynamics. A proper way to minimize unsteady aerodynamic loads on rotor blades is to apply active flow control elements. Such solutions however require appropriate sensors and control strategies in order to ensure a stable operation. Designing a conventional controller for active flow control elements on a real wind turbine blade requires a very large amount of physical insights. However, the aerodynamics and aeroelastic effects on wind turbine blades are not yet well understood. Because of this lack, a feasible way of designing a controller is to use the so-called black box method. Thereby the controller is designed by observing inputs and outputs without taking into account the dynamics in between. http://www.ewec2010proceedings.info/ewea2011/papers/170.pdf EWEA 2011 (European Wind Energy Association), Brussels, Belgium, 14-17 March O.Eisele G.Pechlivanoglou C. N.Nayeri C. O.Paschereit inproceedings Schimek2011c 2011 AIAA paper no. 2011-5702 47th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, San Diego, California, Jul 31 -- Aug 3 S.Schimek J. P.Moeck C. O.Paschereit inproceedings Kruger2011c 2011 AIAA paper 2011-3549 1--14 The isothermal flow dynamics of a generic swirl burner are studied employing large eddy simulation (LES). A sensitivity analysis was conducted, considering different mesh sizes and subgrid-scale models and the results were compared to experimental data. It was found that the overall influence of the computational grid and the subgrid-scale model was neglectable and the simulations were in line with the experiments. A dominant frequency was found in the turbulent kinetic energy spectrum representing a coherent structure. Moreover, by applying the proper orthogonal decomposition (POD) this structure could be identified as a convective helical instability. This helical instability and can be represented by a pair of modes, and is assumed to be triggered by a precessing vortex core (PVC). 20th AIAA Computational Fluid Dynamics Conference, June 27-30, 2011, Honolulu, Hawaii, USA O.Krüger C.Duwig K.Göckeler S.Terhaar C.Strangfeld C. O.Paschereit L.Fuchs inproceedings Goeke2011b 2011 AIAA paper no. 2011-5535 47th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, San Diego, California, Jul 31 -- Aug 3 S.Göke S.Schimek A.Fateev S.Clausen P.Kuhn S.Terhaar C. O.Paschereit inproceedings Kruger2011b 2011 1--6 The present study employs large eddy simulations (LES) to investigate a generic swirl-stabilized burner operated with methane at ultra-wet conditions. In order to investigate the reactive flow, a customized solver for handling low Mach number flows based on an implicit LES approach was developed. A reduced 4 steps / 7 species global scheme was used as combustion model . To compare the simulations with experiments, OH chemiluminescence pictures served as a reference. Kruger2011b.pdf Proceedings of the European Combustion Meeting 2011, Jun 29 – Jul 1, Cardiff, UK O.Krüger C.Duwig S.Göke C. O.Paschereit L.Fuchs inproceedings vey2011 2011 2 614-625 http://toc.proceedings.com/10945webtoc.pdf Proc. 51st Israel Annual Conference on Aerospace Sciences 2011, Feb 23-24, Tel-Aviv and Haifa, Israel 978-1-61782-401-2 S.Vey C. N.Nayeri D.Greenblatt C. O.Paschereit inproceedings Sieber2011 2011 http://www.it.cas.cz/files/DT2011/Sieber_A.pdf

Prague

Colloquium Fluid Dynamics, Institute of Thermomechanics AS CR, v.v.i., Prague, 19--21 Oct M.Sieber K.Oberleithner C. N.Nayeri C. O.Paschereit inproceedings Terhaar2011 2011 AIAA paper no. 2011-3584 1--14 The flow field of a swirl-stabilized burner for ultra-wet combustion is experimentally investigated by assessing the isothermal and the reacting flow. The ultra-wet combustion technique promises high cycle efficiency and low NOx emissions. Investigations of the non- reacting flow field are carried out in a water tunnel facility and the reacting flow is assessed in an atmospheric combustion test rig. Experiments were conducted at a theoretical swirl number of 0.7 and Reynolds numbers in the range of 22,000 to 32,000. Particle Image Velocimetry and OH-Chemiluminescence are employed to measure the flow velocities as well as the spatial distribution of heat release. The effect of steam addition up to levels of 30% of the air mass flow is investigated for natural gas fuel and mixtures of natural gas and hydrogen. The results show a strong impact of steam addition on the flow field and the position of the reaction zone. In particular, three different flow patterns were found. Dry flames and hydrogen flames show a broad inner recirculation zone with very low local turbulent kinetic energy. At high rates of steam dilution, the flow fields show good agreement to the non-reacting flow field in water as well as in isothermal air. At intermediate to high steam dilution rates the flame shows a trumpet like shape. Several sudden changes of the flow field and flame shapes could be observed for various operating conditions. Proc. 41st AIAA Fluid Dynamics Conference and Exhibit, 27-30 June, Honolulu, Hawaii 978-1-61839167-4 (DVD) S.Terhaar K.Göckeler S.Schimek S.Göke C. O.Paschereit inproceedings Kruger2011a 2011 ASME paper GT2011-45866 The present study focuses on the numerical investigation of a generic swirl-stabilized burner operated with methane at ultra-wet conditions. The burner is fed with a preheated homogeneous mixture formed by steam and air. As a set of operating conditions atmospheric pressure, inlet temperature of 673 K, equivalence ratio of 0: 85 and a steam content of 30% is applied. Large eddy simulations have been performed to investigate the flow features. In a first step the non-reacting flow field was in-vestigated with water as working medium. Comparison with Par-ticle Image Velocimetry (PIV) and Laser-Doppler Velocimetry (LDV) measurements conducted in a water tunnel facility showed that an excellent agreement within the experimental uncertainty is obtained for the flow field. A dominant frequency in the tur-bulent energy spectrum was identified, which corresponds to the motion associated with a precessing vortex core (PVC). In order to investigate the reactive flow in a second step, a customized solver for handling low Mach number reacting flows based on an implicit LES approach was developed. As reaction mechanism a reduced 4 steps / 7 species global scheme was used. To compare the simulations qualitatively with a wet flame, OH chemiluminescence pictures serve as a reference. The simula-tions showed a more compact flame compared to the OH pic-tures. Nevertheless, the prolongation and position of the flame were found to be reasonable. The reduced mechanism captures the main effects, such as the reduction of the peak and mean temperatures. Furthermore, the presence of a PVC in the react- ing flow could be determined and was not suppressed by heat- release. Proc. ASME Turbo Expo 2011: Advancing Clean and Efficient Turbine Technology (GT2011), June 6-10, Vancouver, BC, Canada O.Krüger C.Duwig S.Göke K.Göckeler C. O.Paschereit L.Fuchs inproceedings Oberleithner2011b 2011 318 3 032050 The aim of this work is to control the self-excited global mode that concomitants vortex breakdown in turbulent swirling jets. This mode is characterized by a co-rotating counter winding single helical instability wave that originates from the jet center. Experiments show that the amplitude of this global mode is effectively reduced by exciting a double-helical mode in the outer shear layer. This mode is shown to be convective unstable at growth rates that are well predicted by spatial linear stability analysis. The dampening of the global mode occurs through an energy transfer between the inner and the outer shear layer. In preparation of closed-loop experiments, a reduced order model of the flow dynamics is developed based on five leading POD modes. The model is calibrated to flow�transients recorded via time-resolved PIV. A state estimator is designed that predicts the flow state from two hotwire probes. The performance of the estimator is validated in open-loop experiments. First results support the design of the model and state estimator. http://stacks.iop.org/1742-6596/318/i=3/a=032050 Journal of Physics: Conference Series Warsaw 13th European Turbulence Conference (ETC13) 12–15 September 2011 1742-6588 (Print), 1742-6596 (Online) 10.1088/1742-6596/318/3/032050 K.Oberleithner M.Sieber C. N.Nayeri C. O.Paschereit inproceedings Cosic2011 2011 ASME paper GT2011-46503 Proc. ASME Turbo Expo 2011: Advancing Clean and Efficient Turbine Technology (GT2011), June 6-10, Vancouver, BC, Canada B.Ćosić B.Bobusch J. P.Moeck C. O.Paschereit inproceedings Strangfeld2011a 2011 AIAA-2011-3895 1--12 20th AIAA Computational Fluid Dynamics Conference, June 27-30, 2011, Honolulu, Hawaii, USA C.Strangfeld C. N.Nayeri L.Taubert C. O.Paschereit inproceedings Pechlivanoglou2011b 2011 ASME paper GT2011-45493 A control system consisting of a force sensor, a controller and the microflap as an actuator was designed and tested in the wind tunnel. For this purpose a test wing with constant cross section, based on the dedicated wind turbine airfoil AH 93-W-174 was equipped with a trailing edge microflap with a flap-chord of 1.6%c. Measurements were accomplished at the large wind tunnel of the Herman Föttinger Institute (HFI) of the TU-Berlin. Wind gusts were simulated by varying the angle of attack of the airfoil model with a maximum angular velocity of 2.2°/s. The microflap could be deflected simultaneously with a deflection speed of approximately 300°/s. Proc. ASME Turbo Expo 2011: Advancing Clean and Efficient Turbine Technology (GT2011), June 6-10, Vancouver, BC, Canada G.Pechlivanoglou C. N.Nayeri C. O.Paschereit inproceedings Goeckeler2011 2011 AIAA-2011-3585 13 Reactor network models are widely used in studies of combustion kinetics. The mean residence time in the reactors is a crucial input for these models, however few attempts have been conceived so far to determine it accurately. In this study, the temporal and spatial distribution of a fluorescent tracer, injected as a short pulse, was measured using Highspeed planar laser-induced fluorescence (HS-PLIF), and Particle Image Velocimetry (PIV) was utilized for measuring the flow field. In a pulse experiment the tracer response in the combustor exit stream almost readily yields the residence time density function, which directly gives the mean residence time in the combustor. For a volume element within the combustor, the respective tracer response yields the time delay from the injection until the elements exit, but not its residence time, due to dispersion of the tracer input. The density function describes the deviation from the ideal transport in a plug flow and a perfectly mixed flow by considering two characteristic times: (1) a convective time delay τc, representing the time until the first detection of the tracer, and (2) a dispersive time delay τd, which characterizes the degree of dispersion upstream,and mixing within the respective volume element. A plug flow is solely described by τc, whereas a perfectly mixed flow is characterized only by τd. Time density functions were obtained at the injection holes, the combustion chamber inlet and outlet, as well as in an axicentric cross-section of the combustion chamber. The shape of density functions in the combustion chamber varies between that of an approx- imate plug flow and perfectly mixed flow, but mostly is represented by a superposition of the two. The distribution of τc indicates the path of the tracer through the combus- tor. By means of the τd distribution, zones of similar mixing characteristics are identified. The external recirculation zone (ERZ) is among these; however, only part of the internal recirculation zone (IRZ), that is less effected by entrainment from the jet, exhibits these similar mixing characteristics. Based on the experimental findings, a semi-empirical re- actor network model was developed applying an extended tanks-in-series approach. The model agrees very well with the measured time density functions. The transfer functions of the recirculation zones are used to determine the actual mean residence time in these zones. The mean residence time in the IRZ yields 21% of the total combustor residence time and 25% in the ERZ. Proc. 41st AIAA Fluid Dynamics Conference and Exhibit, 27-30 June, Honolulu, Hawaii 978-1-61839167-4 (DVD) K.Göckeler S.Terhaar A.Lacarelle C. O.Paschereit inproceedings schroedinger2011 2011 AIAA paper no. 2011-5747 47th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, San Diego, California, Jul 31 -- Aug 3 C.Schrödinger A.Lacarelle M.Oevermann C. O.Paschereit inproceedings moeck2011 2011 Proc. of the 18th International Congress on Sound and Vibration (ICSV), July 10-14, Rio de Janeiro, Brazil 978-85-63243-01-0 (CDROM J. P.Moeck C. O.Paschereit article konle2011 Journal of Engineering for Gas Turbines and Power 2010 9 14 133 1 011602 (8 Pages) acoustic measurement; acoustic wave interferometry; fibre optic sensors; microphones http://link.aip.org/link/?GTP/133/011602/1 ASME 0742-4795 (online), 1528-8919 (print) 10.1115/1.4001983 H. J.Konle C. O.Paschereit I.Röhle article Bothien2010 Journal of Engineering for Gas Turbines and Power 2010 8 20 32 12 121502 (10 pages) 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. http://link.aip.org/link/?GTP/132/121502/1 ASME 0742-4795 (online), 1528-8919 (print) 10.1115/1.4000806 M. R.Bothien J. P.Moeck C. O.Paschereit article SchuermansGPGP2010 Journal of Engineering for Gas Turbines and Power 2010 8 10 132 11 111503 (9 pages) Thermoacoustic transfer functions of a full-scale gas turbine burner operating under full engine pressure have been measured. The excitation of the high-pressure test facility was done using a siren that modulated a part of the combustion airflow. Pulsation probes have been used to record the acoustic response of the system to this excitation. In addition, the flame's luminescence response was measured by multiple photomultiplier probes and a light spectrometer. Three techniques to obtain the thermoacoustic transfer function are proposed and employed: two acoustic-optical techniques and a purely acoustic technique. The first acoustical-optical technique uses one single optical signal capturing the chemiluminescence intensity of the flame as a measure for the heat release in the flame. This technique only works if heat release fluctuations in the flame have only one generic source, e.g., equivalence ratio or mass flow fluctuations. The second acoustic-optical technique makes use of the different response of the flame's luminescence at different optical wavelengths bands to acoustic excitation. It also works, if the heat release fluctuations have two contributions, e.g., equivalence ratio and mass flow fluctuation. For the purely acoustic technique, a new method was developed in order to obtain the flame transfer function, burner transfer function, and flame source term from only three pressure transducer signals. The purely acoustic method could be validated by the results obtained from the acoustic-optical techniques. The acoustic and acoustic-optical methods have been compared and a discussion on the benefits and limitations of each is given. The measured transfer functions have been implemented into a nonlinear, three-dimensional, time domain network model of a gas turbine with an annular combustion chamber. The predicted pulsation behavior shows a good agreement with pulsation measurements on a field gas turbine. http://link.aip.org/link/?GTP/132/111503/1 ASME 0742-4795 (online), 1528-8919 (print) 10.1115/1.4000854 B.Schuermans F.Guethe D.Pennell D.Guyot C. O.Paschereit article Bothien2010a Journal of Engineering for Gas Turbines and Power 2010 6 17 132 9 091503 (10 pages) In the design process, new burners are generally tested in combustion test rigs. With these experiments, as well as with computational fluid dynamics, finite element calculations, and low-order network models, the burner's performance in the full-scale engine is sought to be predicted. Especially, information about the thermoacoustic behavior and the emissions is very important. As the thermoacoustics strongly depend on the acoustic boundary conditions of the system, it is obvious that test rig conditions should match or be close to those of the full-scale engine. This is, however, generally not the case. Hence, if the combustion process in the test rig is stable at certain operating conditions, it may show unfavorable dynamics at the same conditions in the engine. In previous works, the authors introduced an active control scheme, which is able to mimic almost arbitrary acoustic boundary conditions. Thus, the test rig properties can be tuned to correspond to those of the full-scale engine. The acoustic boundary conditions were manipulated using woofers. In the present study, an actuator with higher control authority is investigated, which could be used to apply the control scheme in industrial test rigs. The actuator modulates an air mass flow to generate an acoustic excitation. However, in contrast to the woofers, it exhibits a strong nonlinear response regarding amplitude and frequency. Thus, the control scheme is further developed to account for these nonlinear transfer characteristics. This modified control scheme is then applied to change the acoustic boundary conditions of an atmospheric swirl-stabilized combustion test rig. Excellent results were obtained in terms of changing the reflection coefficient to different levels. By manipulating its phase, different resonance frequencies could be imposed without any hardware changes. The nonlinear control approach is not restricted to the actuator used in this study and might therefore be of use for other actuators as well. http://link.aip.org/link/?GTP/132/091503/1 ASME 0742-4795 (online), 1528-8919 (print) 10.1115/1.4000599 M. R.Bothien C. O.Paschereit article Albrecht2010 Journal of Engineering for Gas Turbines and Power 2010 1 12 132 4 041501 (8 pages) Premixed flames of swirl-stabilized combustors (displaced half-cone) are susceptible to thermo-acoustic instabilities, which should be avoided under all operating conditions in order to guarantee a long service life for both stationary and aircraft gas turbines. The source of this unstable flame behavior can be found in a transition of the premix flame structure between two stationary conditions that can be easily excited by fuel fluctuations, coherent structures within the flow, and other mechanisms. Pilot flames can alleviate this issue either by improving the dynamic stability directly or by sustaining the main combustion process at operating points where instabilities are unlikely. In the present study, the impact of two different premixed pilot injections on the combustion stability is investigated. One of the pilot injector (pilot flame injector) was located upstream of the recirculation zone at the apex of the burner. The second one was a pilot ring placed at the burner outlet on the dump plane. A noticeable feature of the pilot injector was that an ignition device allowed for creating pilot premixed flames. The present investigation showed that these premixed pilot flames were able to suppress instabilities over a wider fuel/air ratio range than the conventional premixed pilot injection alone. Furthermore, it was possible to prevent instabilities and maintain the flame burning near the lean blowout when a percentage of the fuel was premixed with air and injected through the pilot ring. NOx emissions were significantly reduced. Ehttp://link.aip.org/link/?GTP/132/041501/1 ASME 0742-4795 (online), 1528-8919 (print) 10.1115/1.3019293 P.Albrecht S.Bade A.Lacarelle C. O.Paschereit E. J.Gutmark article Konle2010 Measurement Science and Technology 2010 21 1 015302 A high-temperature resistant fiber-optical microphone (FOM) was developed and successfully applied in a combustion chamber (~1.2 × 105 Pa, ~1400 K gas temperature) with thermo-acoustic oscillations resulting in a sound pressure level of 154 dB at the dominant frequency. The core of the optical set-up used for the FOM is a Fabry–Perot interferometer. To create an acoustical sensor based on this type of interferometer, a new method of generation and postprocessing of the interference signal was developed. The simple replaceability of the used membrane material allows the adaptation of the sensor sensitivity to the projected field of application. http://iopscience.iop.org/0957-0233/21/1/015302/pdf/0957-0233_21_1_015302.pdf 0957-0233 (Print), 1361-6501 (Online) 10.1088/0957-0233/21/1/015302 H. J.Konle I.Röhle C. O.Paschereit article Lacarelle2010 AIAA Journal 2010 48 8 1708-1720 00011452 10.2514/1.J050188 A.Lacarelle D. M.Luchtenburg M. R.Bothien B. R.Noack C. O.Paschereit article Paschereit2010 "Energien für die Zukunft", Zeitschrift für Internationale Absolventen der Technischen Universität Berlin 2010 65 6-7 http://www.alumni.tu-berlin.de/fileadmin/Redaktion/ABZ/PDF/TUI/65/paschereit_TUI65.pdf C. O.Paschereit article Paschereit2010a η[energie] Energieeffizienz & kohlenstoffarme Energietechnik 2010 2 8-11 Mit einem völlig neuen Ansatz entwickelt der Lehrstuhl für Strömungsmechanik an der TU Berlin ein Verfahren, das die Verbrennung in Gasturbinen den Anforderungen einer modernen Energiepolitik anpasst: Bei geringerem Ressourcenverbrauch soll eine höhere Effizienz erreicht werden. Gleichzeitig werden Gasturbinen für die Verbrennung alternativer Rohstoffe fit gemacht. Prof. Dr. Christian Oliver Paschereit und Sebastian Göke berichten über dieses Vorhaben, das von der EU mit großzügigen Fördermitteln ausgezeichnet wurde. http://www.etaenergie.com/news/9,237376/%CE%B7%5Benergie%5D-2-2010/Verbrennung-von-Gasen.html succidia AG C. O.Paschereit S.Göke conference Oberleithner2010c 2010 63rd Annual DFD Meeting American Physical Society K.Oberleithner C. N.Nayeri C. O.Paschereit I.Wygnanski conference Oberleithner2010d 2010 Altes Koenigliches Kurhaus, Bad Reichenhall, Germany 8th Euromech Fluid Mechanics Conference K.Oberleithner C. N.Nayeri C. O.Paschereit I.Wygnanski inproceedings Moeck2010 2010 4 108 291--306 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. King, R. Springer-Verlag Berlin Notes on Numerical Fluid Mechanics and Multidisciplinary Design Active Flow Control II, Papers Contributed to the Conference ''Active Flow Control II 2010'', Berlin, Germany, May 26 to 28, 2010 978-3-642-11734-3 (print), 978-3-642-11735-0 (online) 10.1007/978-3-642-11735-0_19 J. P.Moeck C.Scharfenberg C. O.Paschereit R.Klein inproceedings Lacarelle2010a 2010 4 108 307--321 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. King, Rudibert Springer-Verlag Berlin Notes on Numerical Fluid Mechanics and Multidisciplinary Design Active Flow Control II, Papers Contributed to the Conference ''Active Flow Control II 2010'', Berlin, Germany, May 26 to 28, 2010 978-3-642-11734-3 (print), 978-3-642-11735-0 (online) 10.1007/978-3-642-11735-0_20 A.Lacarelle J. P.Moeck C. O.Paschereit G.Gelbert R.King D. M.Luchtenburg B. R.Noack J.Kasten H. C.Hege inproceedings Lacarelle2010c 2010 ASME paper GT2010-23132 919-931 The feasibility of using cold flow measurements in a conical swirl-inducing burner to predict the fuel/air mixture probability density function (PDF) at the flame location in a staged premixed swirl-inducing burner is discussed in the present work. Particle Image Velocity (PIV) measurements are used to investigate the impact of the flame on the mean and coherent velocity field upstream of the premixed flame of a conical swirl-inducing burner. When the flame does not anchor inside the burner, a good agreement between the reacting and the cold-flow fields is ensured. The scalar mixing field, dominated by coherent concentration fluctuations, is thus marginally affected by the flame. In this case, a correction of the mixture PDF, recorded in a water test rig at the burner outlet with planar laser-induced fluorescence (PLIF), can be used to estimate the mixture PDF at the flame location. This correction is based on the exponential decay of the mixture variance associated with the flame-position information of the reacting flow. An experimental curve fitting and a chemical-reactor network model confirm that the resulting PDF approximates the real unmixedness at the flame better than the measured mixture PDF at the burner outlet. When the flame is anchored inside the burner, the correction approach does not apply anymore, due to the strong flow field changes. The methodology presented allows to quantitatively predict the mixture PDF at the flame location for different total powers, preheating temperatures, and equivalence ratios. The simple mixing model and reactor network model are able to satisfyingly capture the NOx emissions when the flame stabilizes completely downstream of the burner. http://link.aip.org/link/abstract/ASMECP/v2010/i43970/p919/s1 ASME Proc. ASME Turbo Expo 2010: Power for Land, Sea, and Air (GT2010), June 14–18, Glasgow, Scotland 978-0-7918-4397-0 10.1115/GT2010-23132 A.Lacarelle S.Göke C. O.Paschereit inproceedings Pechlivanoglou2010 2010 AIAA paper no. 2010-644 http://pdf.aiaa.org/preview/2010/CDReadyMASM10_1812/PV2010_644.pdf 48th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition, January 4 - 7, 2010, Orlando, Florida, USA G.Pechlivanoglou J.Wagner C. N.Nayeri C. O.Paschereit inproceedings Singh2010 2010 AIAA paper no. 2010-4417 http://pdf.aiaa.org/preview/2010/CDReadyMFD10_2119/PV2010_4417.pdf 5th Flow Control Conference, 28 June - 1 July, 2010, Chicago, Illinois, USA Y.Singh H.Mueller-Vahl D.Greenblatt C. N.Nayeri C. O.Paschereit inproceedings Moeck2010a 2010 Proc. DAGA 2010, Berlin, Germany J. P.Moeck G.Gelbert M.Paul C. O.Paschereit R.King inproceedings Schimek2010 2010 ASME paper GT2010-22827 665-675 http://link.aip.org/link/abstract/ASMECP/v2010/i43970/p665/s1 ASME Proc. ASME Turbo Expo 2010: Power for Land, Sea, and Air (GT2010), June 14–18, Glasgow, Scotland 978-0-7918-4397-0 10.1115/GT2010-22827 S.Schimek J. P.Moeck C. O.Paschereit inproceedings Konle2010a 2010 ASME paper no. GT2010-22022 1--10 A high temperature resistant fiber optical microphone (FOM) was developed and successfully applied in a combustion chamber at a thermal power of 8.4kW to measure thermo-acoustic oscillations at a frequency of 85Hz and a sound pressure level of 154dB. The sensor head temperature was estimated to ~ 1000K. The core of the optical setup used for the FOM is a Fabry-Perot interferometer. To create an acoustical sensor based on this type of interferometer, a new method of generation and postprocessing of the interference signal was developed. The simple replaceability of the sensor membrane reduces the requirements concerning the sensor handling compared to conventional condenser microphones and allows the adaption of the sensor sensitivity to its application case changing the membrane stiffness. http://link.aip.org/link/abstract/ASMECP/v2010/i43987/p1/s1 ASME Proc. ASME Turbo Expo 2010: Power for Land, Sea, and Air (GT2010), June 14–18, Glasgow, Scotland 978-0-7918-4398-7 10.1115/GT2010-22022 H. J.Konle I.Röhle C. O.Paschereit inproceedings Schroedinger2010 2010 GT2010-22910 777-789 In this paper, we investigate the feasibility and limitation of modeling non reacting and reacting flows of a premixed burner with steady RANS. The burner investigated here is a standard industrial swirl-inducing burner equipped with a staging of fuel injection. The simulation results on mixing quality, flame shape and position and convective time delays are compared to measurements which are performed in a water test rig and in a combustion chamber. The RANS simulations can qualitatively capture the trends observed from experimental data. The simulated mixing quality evolves in a similar way as the experimental data when the fuel distribution is changed. Using a turbulent Schmidt number of 0.2, the absolute values are in good agreement with the measured ones. Variations of the fuel injection distribution lead to changes in the flame shape and its stabilization location. The simulated reacting flow optimized with respect to the turbulent Schmidt/Prandtl number (Sct /Prt = 0.55) is able to predict the changes in flame shape and flame position. However, the shifting of the flame is not as distinct as observed in the experiments. This explains that variations in simulated convective time delays are also smaller than in reality. Nevertheless, the qualitative characteristics of the time delays depending on the fuel distribution parameter can be reproduced and absolute values are generally similar to those of the measurements. http://link.aip.org/link/abstract/ASMECP/v2010/i43970/p777/s1 ASME Proc. ASME Turbo Expo 2010: Power for Land, Sea, and Air (GT2010), June 14–18, Glasgow, Scotland 978-0-7918-4397-0 10.1115/GT2010-22910 C.Schrödinger O.Krüger A.Lacarelle M.Oevermann C. O.Paschereit inproceedings guyot2010b 2010 2010 GT2010-23135 933-944 In this work the relationship between the ratio of the global CH* and OH* flame chemiluminescece and the global equivalence ratio of a technically premixed swirl-stabilized flame is investigated. The burner allows for a modification of the premix fuel injection pattern. The global flame chemiluminescence is monitored by a high-sensitivity light spectrometer and multiple photo-multipliers. The photo-multipliers were equipped with narrow optical band-pass filters and recorded the flame's OH*, CH* and CO2* chemiluminescence intensity. To ensure an approximately uniform equivalence ratio distribution in the combustion zone, the spatial OH* and CH* flame chemiluminescence was recorded simultaneously with one ICCD camera using a special optical setup, which incorporated among other things one fully reflective and one semi-reflective mirror and appropriate optical filters. The flame chemiluminescence intensity was mapped for a range of equivalence ratios and air mass flows. The mapping shows that (as stated for perfectly premixed flames in the literature) the OH*, CH* and CO2* intensity of the investigated flame depends linearly on the air mass flow and exponentially on the equivalence ratio. Hence for the investigated operating conditions (i.e., quasi premix conditions) the global CH*/OH* intensity can be employed as a measure of the global equivalence ratio for the operating conditions investigated in this work. However, the contribution of broadband CO2* chemiluminescence in the wave length range of CH* chemiluminescence has to be accounted for. http://link.aip.org/link/abstract/ASMECP/v2010/i43970/p933/s1 ASME Proc. ASME Turbo Expo 2010: Power for Land, Sea, and Air (GT2010), June 14–18, Glasgow, Scotland 978-0-7918-4397-0 10.1115/GT2010-23135 D.Guyot F.Guethe B.Schuermans A.Lacarelle C. O.Paschereit inproceedings Goeke2010 2010 ASME paper no. GT2010-23417 1125--1135 Humidified gas turbines (HGT), operating with humidified air, promise a higher efficiency compared to dry gas turbines, as well as reduced NOx emissions. In this study, premixed, near-stoichiometric combustion was investigated for gas turbine applications at ultra wet conditions with steam levels up to 35w%. Based on a generic burner, an experimental study was conducted for the combustion of natural gas at atmospheric pressure. The influence of humidity on emissions and flammability limits was investigated for different inlet temperatures, swirl numbers, and fuel injection strategies. At near-stoichiometric conditions, a degree of humidity of 35w% was achieved with a stable flame and single-digit NOx and CO emissions. In experiments conducted in a water tunnel, the flow field of the combustor was investigated using Laser Doppler Anemometry and Laser-induced Fluorescence. In addition to the experiments, a kinetic assessment of the emission formation was conducted with a reactor network, using a combination of several perfectly stirred reactors. The results of these simulations confirm the experimental findings. http://link.aip.org/link/abstract/ASMECP/v2010/i43970/p1125/s1 Proc. ASME Turbo Expo 2010: Power for Land, Sea, and Air (GT2010), June 14–18, Glasgow, Scotland 978-0-7918-4397-0 10.1115/GT2010-23417 S.Göke K.Göckeler O.Krüger C. O.Paschereit inproceedings Goeckeler2010 2010 Proceedings of 3rd International Conference on Jets, Wakes and Separated Flows (ICJWSF), Cincinnati, Ohio K.Göckeler S.Göke S.Schimek C. O.Paschereit inproceedings Pfeifer2010 2010 36. Deutsche Jahrestagung für Akustik, Dresden, 15.03. - 18.03.2010 C.Pfeifer B.Pardowitz C. O.Paschereit L.Enghardt inproceedings Pechlivanoglou2010a 2010 http://10.dewek.de/fileadmin/pdf/abstracts/S15_3.pdf Proceedings of DEWEK 2010, 17-18 November 2010, Bremen, Germany G.Pechlivanoglou C. N.Nayeri C. O.Paschereit inproceedings Eisele2010 2010 http://smart-blade.com/fileadmin/downloads/abstract_plasma.pdf Proceedings of DEWEK 2010, 17-18 November 2010, Bremen, Germany O.Eisele G.Pechlivanoglou C. N.Nayeri C. O.Paschereit inproceedings Oberleithner2010b 2010 Proceedings of 3rd International Conference on Jets, Wakes and Separated Flows (ICJWSF), Cincinnati, Ohio K.Oberleithner P.Kuhn C. N.Nayeri C. O.Paschereit I.Wygnanski inproceedings Marten2010a 2010 http://10.dewek.de/fileadmin/pdf/abstracts/S15_4.pdf Proceedings of DEWEK 2010, 17-18 November 2010, Bremen, Germany D.Marten G.Pechlivanoglou C. N.Nayeri C. O.Paschereit inproceedings Konle2010b 2010 36. Deutsche Jahrestagung für Akustik, Fortschritte der Akustik - DAGA 2010, 15.-18. März 2010 Berlin, Germany H. J.Konle I.Röhle C. O.Paschereit inproceedings Vey2010 2010 AIAA paper no. 2010-4865 http://pdf.aiaa.org/preview/2010/CDReadyMFD10_2120/PV2010_4865.pdf 40th Fluid Dynamics Conference and Exhibit, June 28 - July 1, 2010, Chicago, Illinois S.Vey D.Greenblatt C. N.Nayeri C. O.Paschereit inproceedings Moeck2010b 2010 Technische Universität München Proceedings of the Int'l Summer School and Workshop on Non-Normal and Nonlinear Effects in Aero- and Thermoacoustics J. P.Moeck C. O.Paschereit inproceedings Vey2010a 2010 AIAA paper no. 2010-1222 http://pdf.aiaa.org/preview/2010/CDReadyMASM10_1812/PV2010_1222.pdf 48th AIAA Aerospace Science Meeting, January 4 - 7, 2010, Orlando, Florida, USA S.Vey C. N.Nayeri C. O.Paschereit D.Greenblatt inproceedings Lacarelle2010b 2010 AIAA paper no. 2010-1332 http://pdf.aiaa.org/preview/2010/CDReadyMASM10_1812/PV2010_1332.pdf 48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition, Jan. 4-7, 2010, Orlando, Florida, USA A.Lacarelle L.Matho C. O.Paschereit inproceedings Kastantin2010 2010 AIAA paper no. 2010-4864 http://pdf.aiaa.org/preview/2010/CDReadyMFD10_2120/PV2010_4864.pdf 40th Fluid Dynamics Conference and Exhibit, 28 June - 1 July 2010, Chicago, Illinois Y.Kastantin S.Vey C. N.Nayeri C. O.Paschereit inproceedings Pechlivanoglou2010b 2010 ASME paper no. GT2010-23258 845-855 The effects of distributed roughness on wind turbines are extensively investigated in this paper. The sources of roughness are identified and analyzed and their effects on airfoil are estimated from simulations and measured with wind tunnel measurements. In addition to the environmental and manufacturing induced roughness, several forms of roughness-related shape deviations are investigated and their effects on the aerodynamic performance of airfoils is qualitatively predicted through numerical simulations. The actual effects of roughness on wind turbine performance are also presented through power production measurements of wind turbines installed in sandy environments. These measurements are correlated with simulated power predictions, utilizing a steady state BEM code. http://link.aip.org/link/abstract/ASMECP/v2010/i44007/p845/s1 ASME Proc. ASME Turbo Expo 2010: Power for Land, Sea, and Air (GT2010), June 14–18, Glasgow, Scotland 978-0-7918-4400-7 10.1115/GT2010-23258 G.Pechlivanoglou S.Führ C. N.Nayeri C. O.Paschereit inproceedings Moeck2010c 2010 ASME paper no. GT2010-23577 1219-1232 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. http://link.aip.org/link/abstract/ASMECP/v2010/i43970/p1219/s1 ASME Proc. ASME Turbo Expo 2010: Power for Land, Sea, and Air (GT2010), June 14–18, Glasgow, Scotland 978-0-7918-4397-0 10.1115/GT2010-23577 J. P.Moeck M.Paul C. O.Paschereit miscellaneous Paschereit2010b 2010 Invited Talk, 3rd International Conference on Jets, Wakes and Separated Flows (ICJWSF), Cincinnati, Ohio C. O.Paschereit article Moeck2009 Proceedings of the Combustion Institute 2009 32 1 1199-1207 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 5λ/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. 1540-7489 10.1016/j.proci.2008.05.062 J. P.Moeck M.Oevermann R.Klein C. O.Paschereit H.-J.Schmidt article Guyot2009 International Journal of Flow Control 2009 1 2 155-166 http://multi-science.metapress.com/content/y114p22636211h45/fulltext.pdf 1756-8250 (Print) 10.1260/175682509788913335 D.Guyot C. O.Paschereit S.Raghu article Bothien2009a Journal of Engineering for Gas Turbines and Power 2009 131 2 021502 (10 pages) http://link.aip.org/link/?GTP/131/021502/1 ASME 0742-4795 (online), 1528-8919 (print) 10.1115/1.2969088 M. R.Bothien J. P.Moeck C. O.Paschereit article Konle2009 International Journal of Spray and Combustion 2009 1 2 251-281 Thermo-acoustic investigations require reliable measurement techniques in hot environments for pressure, density fluctuations with a high dynamic range and acoustic particle velocity. This paper presents recent developments of optical measurement techniques in combustion diagnostics. A fibre-optic microphone based on the interferometric detection of membrane deflections was designed to measure acoustic pressure oscillations. Due to the heat resistant design, the sensor has an upper temperature limitation of approximately 970 K. Rayleigh-Scattering measurements, using the density dependent intensity of scattered light were performed in an unconfined flame with approximately 1600 K to study amplitude and phase distribution of the flame pulsation. Acoustic particle velocity can be determined applying acoustic PIV (particle image velocimetry) technique. This paper shows a way to measure simultaneously the acoustic particle velocity and the locally resolved mean flow velocity of a turbulent flow. Together these non-invasive techniques are applicable to study thermo-acoustic processes and sound generation in combustion chambers or turbines. http://lambda.qsensei.com/content/164v7m H. J.Konle A.Rausch A.Fischer U.Doll C.Willert C. O.Paschereit I.Röhle article Greenblatt2009 AIAA Journal 2009 47 12 2845-2856 10.2514/1.41767 D.Greenblatt S.Vey C. O.Paschereit R.Meyer article Lacarelle2009b Journal of Engineering for Gas Turbines and Power 2009 131 3 031504-1 (12 pages) http://link.aip.org/link/?GTP/131/031504/1 ASME 0742-4795 0742-4795 (online), 1528-8919 (print) 10.1115/1.2982139 A.Lacarelle T.Faustmann D.Greenblatt C. O.Paschereit O.Lehmann D. M.Luchtenburg B. R.Noack conference KrugerSP2009 2009 11 18 ANSYS Conference & 27th CADFEM Users Meeting Leipzig, Germany ANSYS Conference & 27th CADFEM Users Meeting November 18-20, 2009 3-937523-06-5 O.Krüger A.Spille-Kohoff C. O.Paschereit inproceedings Singh2009 2009 Proceedings of the 6th International Symposium on Turbulence and Shear Flow Phenomena (TSFP6), June 22-24, Seoul, South Korea Y.Singh D.Greenblatt C. N.Nayeri C. O.Paschereit inproceedings Bothien2009 2009 ASME paper GT2009-60016 773-786 In the design process, new burners are generally tested in combustion test rigs. With these experiments, as well as with CFD, finite element calculations, and low-order network models, the burner's performance in the full-scale engine is sought to be predicted. Especially, information about the thermoacoustic behaviour and the emissions is very important. As the thermoacoustics strongly depend on the acoustic boundary conditions of the system, it is obvious that test rig conditions should match or be close to those of the full-scale engine. This is, however, generally not the case. Hence, if the combustion process in the test rig is stable at certain operating conditions, it may show unfavourable dynamics at the same conditions in the engine. In previous works, the authors introduced an active control scheme which is able to mimic almost arbitrary acoustic boundary conditions. Thus, the test rig properties can be tuned to correspond to those of the full-scale engine. The acoustic boundary conditions were manipulated using woofers. In the present study, an actuator with higher control authority is investigated, which could be used to apply the control scheme in industrial test rigs. The actuator modulates an air mass flow to generate an acoustic excitation. However, in contrast to the woofers, it exhibits a strong non-linear response regarding amplitude and frequency. Thus, the control scheme is further developed to account for these non-linear transfer characteristics. This modified control scheme is then applied to change the acoustic boundary conditions of an atmospheric swirl-stabilized combustion test rig. Excellent results were obtained in terms of changing the reflection coefficient to different levels. By manipulating its phase, different resonance frequencies could be imposed without any hardware changes. The non-linear control approach is not restricted to the actuator used in this study and might therefore be of use for other actuators as well. http://link.aip.org/link/abstract/ASMECP/v2009/i48838/p773/s1 Proc. ASME Turbo Expo 2009: Power for Land, Sea, and Air (GT2009), June 8-12, Orlando, Florida, USA 9780791838495 (DVD), 978-0-7918-4883-8 (online) 10.1115/GT2009-60016 M. R.Bothien C. O.Paschereit inproceedings Oberleithner2009 2009 MinnowbrookVI Workshop Syracuse University K.Oberleithner C. O.Paschereit I.Wygnanski inproceedings Schimek2009 2009 M. Pawelczyk and D. Bismor (Hrsg.), 16th International Congress of Sound and Vibration, Krakov, Poland 978-83-60716-71-7 (CD-Rom) S.Schimek J. P.Moeck C. O.Paschereit inproceedings Nayeri2009 2009 179-191 Browand, McCallen, Ross Lecture Notes in Applied and Computational Mechanics 41 "The Aerodynamics of Heavy Vehicles II: Trucks, Buses and Trains" 1613-7763 C. N.Nayeri D.Greenblatt J.Haff C. O.Paschereit L.Löfdahl inproceedings Lacarelle2009 2009 AIAA paper no. AIAA-2009-986 47th AIAA Aerospace Sciences Meeting including The New Horizons Forum and Aerospace Exposition, Jan. 5-8, 2009, Orlando, Florida, USA 1-56347-969-9 (DVD) A.Lacarelle J. P.Moeck A.Tenham C. O.Paschereit inproceedings Bothien2009c 2009 Volume 2: Combustion, Fuels and Emissions ASME paper GT2009-60019 787-798 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. http://link.aip.org/link/abstract/ASMECP/v2009/i48838/p787/s1 Proc. ASME Turbo Expo 2009: Power for Land, Sea, and Air (GT2009), June 8-12, Orlando, Florida, USA 978-0-7918-3849-5 (CD-ROM), 978-0-7918-4883-8 10.1115/gt2009-60019 M. R.Bothien J. P.Moeck C. O.Paschereit inproceedings Harr2009 2009 ASME paper GT2009-59204 55-62 The present paper shows the current state of a feasibility study of the University of Applied Sciences Esslingen. The intention of this study is the conversion of a model-turbine into a turboshaft-engine for variable applications, with as few as possible modifications. The shaft power of the engine is estimated on 20 kW at least. It is intended to use a recuperator to augment its efficiency. After a general introduction possible applications are discussed and the previous design-process is explained: Subsequent to the concept-phase cycle parameters were calculated and the power turbine was designed and manufactured. At present turbine tests are running. The recuperator is of counter flow type. To shorten the flow path it is mounted directly around the combustor. Currently different variations are being designed which will be optimised. The pressure loss within the exhaust manifold between power turbine and recuperator has already been reduced by simulations and tests. This will be minimised through application of a genetic optimisation software. http://link.aip.org/link/abstract/ASMECP/v2009/i48869/p55/s1 ASME Proc. ASME Turbo Expo 2009: Power for Land, Sea, and Air (GT2009), June 8-12, Orlando, Florida, USA 9780791838495 (DVD), 978-0-7918-4886-9 (online) 10.1115/GT2009-59204 C.Harr C. O.Paschereit U.Gärtner inproceedings Pfeifer2009 2009 XVIII 269-291 Schwarz, A. and Janicka, J. Springer-Verlag Berlin Combustion Noise 978-3-642-02037-7 C.Pfeifer C. O.Paschereit J. P.Moeck L.Enghardt inproceedings Oberleithner2009a 2009 Proc. 47th AIAA Aerospace Sciences Meeting including The New Horizons Forum and Aerospace Exposition 1-56347-969-9 (DVD) K.Oberleithner C. O.Paschereit inproceedings Lacarelle2009a 2009 Volume 2: Combustion, Fuels and Emissions ASME paper GT2009-59300 217-229 http://link.aip.org/link/abstract/ASMECP/v2009/i48838/p217/s1 Proc. ASME Turbo Expo 2009: Power for Land, Sea, and Air (GT2009), June 8-12, Orlando, Florida, USA 978-0-7918-4883-8 10.1115/gt2009-59300 A.Lacarelle J. P.Moeck C. O.Paschereit G.Gelbert R.King inproceedings Moeck2009a 2009 Proceedings of the 16th International Congress on Sound and Vibration, Krakow, Poland 978-83-60716-71-7 (CD-Rom) J. P.Moeck C. O.Paschereit inproceedings Guyot2009a 2009 AIAA paper no. 2009-1236 47th AIAA Aerospace Sciences Meeting including The New Horizons Forum and Aerospace Exposition, Jan. 5-8, 2009 , Orlando, Florida, USA D.Guyot J. P.Moeck C. O.Paschereit B.Schuermans inproceedings Guyot2009b 2009 AIAA Paper 2009-5413 http://pdf.aiaa.org/preview/CDReadyMJPC09_1980/PV2009_5413.pdf Proc. 45th AIAA/ ASME/ SAE/ ASEE Joint Propulsion Conference, Denver, USA 1-56347-976-1 (DVD) D.Guyot C. O.Paschereit inproceedings Emara2009 2009 Proc. 45th AIAA/ ASME/ SAE/ ASEE Joint Propulsion Conference, Denver, USA 1-56347-976-1 (DVD) A.Emara A.Lacarelle C. O.Paschereit inproceedings Albrecht2009 2009 ASME paper GT2009-59181 125-135 A premixed pilot injection with reduced NOx formation is proposed as a fail-safe and simple control method to extend the operating range of gas turbines. Different pilot locations within the combustion chamber were chosen to see the impact of pilot injection flames on the local extinction behavior and on the NOx formation. The pilot flame injector (PFI) represents a device for premixed pilot injection and was located in the center of the swirl burner cone. Moreover, the premixed pilot could be ignited by an embedded spark plug inside the PFI so that the main flame, especially near the lean limit, can be provided with additional radicals at the lower stagnation point of the central recirculation zone. A second pilot injection was located at the combustor dump to inject the pilot fuel/air mixture axially into the shear layer between the central and side recirculation zone. It could be shown for different main air preheat temperatures and with activated PFI flame (at 110 Hz spark frequency), that the premixed pilot is the most efficient control method for local extinction prevention without CO emission increase. Also the NOx emissions keep on similar level as the baseline case. The spark plug might also be replaced by a laser ignition device. The efficiency of laser spark plugs could be already demonstrated under atmospheric conditions in Moesl2008 [1] where different ignition devices are proposed to ignite a swirl-stabilized kerosine mixture. Moreover, former tests with the PFI flame indicate also a method to control instabilities so that high amplitude of p[prime] oscillations could be suppressed. http://link.aip.org/link/abstract/ASMECP/v2009/i48838/p125/s1 ASME Proc. ASME Turbo Expo 2009: Power for Land, Sea, and Air (GT2009), June 8-12, Orlando, Florida, USA 978-0-7918-4883-8 (online) 10.1115/GT2009-59181 P.Albrecht C. O.Paschereit S.Bade F.Dinkelacker E. J.Gutmark inproceedings Emara2009a 2009 ASME paper GT2009-59948 707-716 The swirling flow velocity profiles can be strongly influenced by the outlet conditions of the combustion chamber especially at subcritical flow conditions. The effect of such changes on the mean flow or coherent structures is still unclear. It is investigated in the present work in an industrial swirl inducing burner in cold flow conditions with help of PIV. Proper orthogonal decomposition (POD) as well as acoustic measurements were used to characterize the coherent structures shed from the burner mouth. The combustor length (670, and 2020mm) and the outlet area contraction ratio (1, 0.56, 0.27, and 0.09) are varied. Major changes in the flow field are achieved when using a short combustor and the smallest contraction ratio. For this case, a central jet with streamwise velocity is added to the typical central recirculation zone. The POD analysis of the contraction ratios 1 and 0.09 for the long combustor shows that the first helical mode as well as Kelvin Helmholtz vortices are present with minor changes for both cases. At a contraction ratio of 0.09, some new structures at the jet location and near the combustor wall appear. http://link.aip.org/link/abstract/ASMECP/v2009/i48838/p707/s1 Proc. ASME Turbo Expo 2009: Power for Land, Sea, and Air (GT2009), June 8-12, Orlando, Florida, USA 9780791838495 (DVD), 978-0-7918-4883-8 (online) 10.1115/GT2009-59948 A.Emara A.Lacarelle C. O.Paschereit inproceedings Bachmann2009 2009 1-20 Proc. 49th Israel Annual Conference on Aerospace Sciences, Tel Aviv, Israel 9781605609836 M.Bachmann C. O.Paschereit S.Utehs S.Vey D.Greenblatt inproceedings Konle2009a 2009 Proc. 15th AIAA/CEAS Aeroacoustics Conference, May 2009, Orlando, Florida, USA 978-1-56347-937-0 (CD-ROM) H. J.Konle I.Röhle C. O.Paschereit inproceedings Konle2009b 2009 DEGA Proc. International Conference on Acoustics, German Acoustical Society 978-3-9808659-6-8 (CD-ROM) H. J.Konle I.Röhle C. O.Paschereit inproceedings Schuermans2009 2009 ASME paper GT2009-59605 503-514 Thermoacoustic transfer functions have been measured of a full-scale gas turbine burner operating at full engine pressure. Excitation of the high-pressure test facility was done using a siren that modulated part of the combustion airflow. Pulsation probes have been used to record the acoustic response of the system to this excitation. In addition, the flame's luminescence response was measured by multiple photomultiplier tubes and a light spectrometer. Three techniques to obtain the thermoacoustic transfer function are proposed and employed: two combined acoustical-optical technique and a purely acoustic technique. The first acoustical-optical technique uses one single optical signal capturing the chemiluminescence intensity of the flame as a measure for the heat release in the flame. It only works, if heat release fluctuations in the flame have only one contribution, e.g. equivalence ratio or mass flow fluctuations. The second acoustic-optical acoustic-optical technique makes use of the different response of the flame's luminescence at different optical wavelengths bands to acoustic excitation. It also works, if the heat release fluctuations have two contributions, e.g. equivalence ratio and mass flow fluctuation. For the purely acoustic technique, a new method was developed in order to obtain the flame transfer function, burner transfer function and flame source term from only three pressure transducer signals. The purely acoustic method could be validated by the results obtained from the acoustic-optical techniques. The acoustic and acoustic-optical methods have been compared and a discussion on the benefits and limitations of the methods is given. The measured transfer functions have been implemented into a non-linear, three-dimensional, time domain network model of a gas turbine with an annular combustion chamber. The predicted pulsation behavior shows a good agreement with pulsation measurements on a field gas turbine. http://link.aip.org/link/abstract/ASMECP/v2009/i48838/p503/s1 ASME Proc. ASME Turbo Expo 2009: Power for Land, Sea, and Air (GT2009), June 8-12, Orlando, Florida, USA 9780791838495 (DVD), 978-0-7918-4883-8 (online) 10.1115/GT2009-59605 B.Schuermans F.Güthe D.Pennell D.Guyot C. O.Paschereit inproceedings Hoefener2009 2009 EUROMECH COLLOQUIUM 509 "Vehicle Aerodynamics External Aerodynamics of Railway Vehicles, Trucks, Buses and Cars", 24-26 März 2009, Berlin, Germany L.Hoefener D.Romann C. N.Nayeri Th.Tielkes C. O.Paschereit article Bothien2008 Journal of Sound and Vibration 2008 318 678-701 0022-460X 10.1016/j.jsv.2008.04.046 M. R.Bothien J. P.Moeck C. O.Paschereit article Gutmark2008 Journal of Turbomachinery 2008 130 1 011012 (8 pages) Open-loop control methodologies were used to suppress symmetric and helical thermoacoustic instabilities in an experimental low-emission swirl-stabilized gas-turbine combustor. The controllers were based on fuel (or equivalence ratio) modulations in the main premixed combustion (premixed fuel injection (PMI)) or, alternatively, in the secondary pilot fuel. PMI included symmetric and asymmetric fuel injection. The symmetric instability mode responded to symmetric excitation only when the two frequencies matched. The helical fuel injection affected the symmetric mode only at frequencies that were much higher than that of the instability mode. The asymmetric excitation required more power to obtain the same amount of reduction as that required by symmetric excitation. Unlike the symmetric excitation, which destabilized the combustion when the modulation amplitude was excessive, the asymmetric excitation yielded additional suppression as the modulation level increased. The NOx emissions were reduced to a greater extent by the asymmetric modulation. The second part of the investigation dealt with the control of low frequency symmetric instability and high frequency helical instability by the secondary fuel injection in a pilot flame. Adding a continuous flow of fuel into the pilot flame controlled both instabilities. However, modulating the fuel injection significantly decreased the amount of necessary fuel. The reduced secondary fuel resulted in a reduced heat generation by the pilot diffusion flame and therefore yielded lower NOx emissions. The secondary fuel pulsation frequency was chosen to match the time scales typical to the central flow recirculation zone, which stabilizes the flame in the burner. Suppression of the symmetric mode pressure oscillations by up to 20 dB was recorded. High frequency instabilities were suppressed by 38 dB, and CO emissions reduced by using low frequency modulations with 10% duty cycle. http://link.aip.org/link/?JTM/130/011012/1 0889-504X, 1528-8900 10.1115/1.2749292 C. O.Paschereit E. J.Gutmark article Greenblatt2008a AIAA Journal 2008 46 6 1554-1560 0001-1452 10.2514/1.33808 D.Greenblatt Y.Kastantin C. N.Nayeri C. O.Paschereit article Greenblatt2008b AIAA Journal 2008 46 6 1528-1541 0001-1452 10.2514/1.33388 D.Greenblatt B.Göksel I.Rechenberg C. Y.Schüle D.Romann C. O.Paschereit article Pfeifer2008b Acoustical Society of America Journal 2008 123 3405-+ 10.1121/1.2934112 C.Pfeifer J. P.Moeck L.Enghardt C. O.Paschereit inproceedings Konle2008 2008 http://in3.dem.ist.utl.pt./lxlaser2008 Proc. 14th International Symposium on Applications of Laser Techniques to Fluid Mechanics, Lissabon, Portugal, Juli 2008 H. J.Konle I.Röhle C. O.Paschereit inproceedings Guyot2008 2008 paper no. GT2008-50797 583-595 In this work the performance of a fluidic actuator in an active combustion control scheme is demonstrated. The actuator was tested in two different burner configurations, a bluff body burner and a generic swirl-stabilized burner, where it modulated parts of the fuel flow. The oscillation frequency was controlled by varying the inlet mass flow of the actuator. Fluidic actuators are of special interest for fuel-based active control schemes featuring high frequency fuel flow modulation, as they are much more durable then conventional valves due to the absence of fast moving parts. Hot wire measurements were performed to investigate the fluidic actuator's oscillation characteristics without combustion. The actuator was then incorporated into a bluff body burner and a swirl-stabilized burner, respectively, where it modulated parts of the fuel flow blended with nitrogen. Pressure and heat release fluctuations in the combustor were recorded and images of the flame were taken. For both burners the heat release response of the flame to fuel flow modulation was first studied during stable combustion. The spectra of the heat release signals showed a clear peak corresponding to the fluidics' oscillation frequency, thus validating the ability of the actuator to influence the combustion process. As the next step, each of the two combustors was operated at conditions that featured a strong low-frequency combustion instability when no fuel was modulated. In case of the bluff body burner applying fuel modulation resulted in attenuation of the combustion instability for some oscillation frequencies. The attenuation was highest when modulating the fuel flow in between the fundamental instability frequency and its subharmonic. Modulating the fuel flow at the subharmonic, however, resulted in an amplification of the instable mode. Also when applied to the swirl burner, the fludics' fuel flow modulation caused a significant reduction of the pressure oscillations, although the actuator could only be operated at oscillation frequencies much lower than the instability frequency due to the attached tubes. The results obtained in this work show that the fluidic actuator in use allows for fuel modulation and hence combustion control without the need for complex and fast moving parts, thus ensuring a long actuator lifetime. This makes the fluidic actuator highly appropriate for application in industrial gas turbines. Proc. of GT2008, ASME Turbo Expo 2008: Power for Land, Sea and Air, 9-13 June 2008, Berlin, Germany 07918-3842-2, 978-0-7918-4313-0 (online) 10.1115/GT2008-50797 D.Guyot C. O.Paschereit S.Raghu inproceedings DepuruMohan2008 2008 Volume 6: Turbomachinery, Parts A, B, and C ASME paper GT2008-50484 815-827 ASME Turbo Expo 2008: Power for Land, Sea and Air, June 9-13, 2008, Berlin, Germany 978-0-7918-4316-1 10.1115/gt2008-50484 N. K. D.Mohan D.Greenblatt C. N.Nayeri C. O.Paschereit P. N.Ramamurthi inproceedings Guyot2008a 2008 AIAA paper no. 2008-4956 Proc. 44th AIAA/ ASME/ SAE/ ASEE Joint Propulsion Conference & Exhibit, Hartford, CT, USA, July 21-23, 2008 978-1-56437-943-4 D.Guyot B.Bobusch C. O.Paschereit S.Raghu inproceedings Singh2008 2008 4 ASME paper ESDA2008-59509 ASME 2008: 9th Biennial Conference on Engineering Systems Design and Analysis (ESDA2008), July 7-9, 2008 , Haifa, Israel 978-0-7918-4838-8 10.1115/esda2008-59509 Y.Singh D.Greenblatt N. K.Depuru Mohan C. N.Nayeri C. O.Paschereit inproceedings Guyot2008b 2008 paper no. AIAA 2008-1058 Proc. 46th AIAA Aerospace Sciences Meeting and Exhibit, 7-10 January 2008, Reno, Nevada, USA 978-1-56347-937-0 D.Guyot P.Taticchi Mandolini Borgia C. O.Paschereit S.Raghu inproceedings Greenblatt2008 2008 paper No. AIAA 2008-4186 Online-Ver\"ffentlichung Proc. 4th Flow Control Conference, Invited Paper, 23-26 June 2008, Seattle, Washington, USA 978-1-56347-942-7 D.Greenblatt C. S.Yao S.Vey C. O.Paschereit R.Meyer inproceedings Bothien2008a 2008 paper no. GT2008-50171 57-69 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. Proc. of GT2008, ASME Turbo Expo 2008: Power for Land, Sea and Air, 9-13 June 2008, Berlin, Germany 978-0-7918-4313-0 (online) 10.1115/GT2008-50171 M. R.Bothien J. P.Moeck C. O.Paschereit inproceedings Konle2008a 2008 Ruck, B. and Leder, A. and Dopheide, D. Proceedings der 16. GALA-Fachtagung "Lasermethoden in der Strömungsmesstechnik", 9. - 11. September 2008, Universität Karlsruhe, Germany 978-3-9805613-4-1 H. J.Konle I.Röhle C. O.Paschereit inproceedings Albrecht2008 2008 AIAA paper no. 2008-1058 Online-Veröffentlichung Proc. 46th AIAA Aerospace Sciences Meeting and Exhibit, 7-10 January 2008, Reno, Nevada, USA 1-56347-937-0 P.Albrecht S.Bade C. O.Paschereit E. J.Gutmark inproceedings Lacarelle2008 2008 AIAA paper no. 2008-1058 Online-Veröffentlichung Proc. 46th AIAA Aerospace Sciences Meeting and Exhibit, 7-10 January 2008, Reno, Nevada, USA 978-1-56347-937-9 A.Lacarelle G.Gelbert R.King C. O.Paschereit inproceedings Kaempf2008 2008 Proceedings of 2nd International Conference on Jets, Wakes and Separated Flows (ICJWSF), Berlin, Germany T.Kämpf C. N.Nayeri C. O.Paschereit inproceedings Schneider2008 2008 Proceedings of 2nd International Conference on Jets, Wakes and Separated Flows (ICJWSF), Berlin, Germany T.Schneider C. Y.Schüle D.Greenblatt C. N.Nayeri C. O.Paschereit inproceedings Vey2008 2008 AIAA paper no. 2008-1058 Online-Veröffentlichung Proc. 46th AIAA Aerospace Sciences Meeting and Exhibit, 7-10 January 2008, Reno, Nevada, USA 1-56347-937-0 S.Vey D.Greenblatt C. O.Paschereit R.Meyer inproceedings Albrecht2008a 2008 ASME paper GT2008-50255 Premixed flames of swirl-stabilized combustors (displaced-half-cone) are susceptible to thermo-acoustic instabilities which should be avoided under all operating conditions in order to guarantee a long service life for both stationary and aircraft gas turbines. The source of this unstable flame behavior can e.g. be found in a transition of the premix flame structure between two stationary conditions that can be easily excited by fuel fluctuations, coherent structures within the flow and other methods. Pilot flames can alleviate this issue by either improving the dynamic stability directly or by sustaining the main combustion process at operating points where instabilities are unlikely. In the present study, the impact of two different premixed pilot injection on the combustion stability is investigated. One of the pilot injector (pilot flame injector, PFI) was located upstream of the recirculation zone at the apex of the burner. The second one was a pilot ring (PR) placed at the burner outlet on the dump plane. A noticeable feature of the pilot injector was that an ignition device allowed for creating pilot premixed flames. The present investigation evidenced that these premixed pilot flames were able to suppress instabilities over a wider fuel/air ratio range than when the conventional premixed pilot injection alone. Furthermore, it was possible to prevent instabilities and maintain the flame burning near the lean blow out when a percentage of the fuel was premixed with air and injected through the pilot ring. In the mean time, NOx emissions were significantly reduced. Proc. of GT2008, ASME Turbo Expo 2008: Power for Land, Sea and Air, 9-13 June 2008, Berlin, Germany 0-7018-3842-2, 978-0-7918-4313-0 (online) 10.1115/GT2008-50255 P.Albrecht S.Bade A.Lacarelle C. O.Paschereit E. J.Gutmark inproceedings Pfeifer2008 2008 2nd International Conference on Jets, Wakes and Separated Flows, Berlin, Sep 16--19, 2008 C.Pfeifer J. P.Moeck L.Enghardt C. O.Paschereit inproceedings Pfeifer2008a 2008 Online-Veröffentlichung 34. Deutsche Jahrestagung für Akustik (DAGA 2008 - Deutsche Arbeitsgemeinschaft für Akustik, Dresden, März 2008) 978-2-9521105-4-9 C.Pfeifer J. P.Moeck L.Enghardt C. O.Paschereit inproceedings Pfeifer2008c 2008 34. Deutsche Jahrestagung für Akustik, Dresden, 10--13 März, 2008 C.Pfeifer J. P.Moeck L.Enghardt C. O.Paschereit inproceedings Gelbert2008 2008 AIAA paper no. 2008-1055 46th AIAA Aerospace Sciences Meeting, 7 - 10 January 2008, Reno, Nevada G.Gelbert J. P.Moeck M. R.Bothien R.King C. O.Paschereit inproceedings King2008 2008 AIAA paper no. 2008-3975 38th Fluid Dynamics Conference and Exhibit, June 23-26, 2008, Seattle, Washington, USA 1-56347-942-7 R.King K.Aleksic G.Gelbert N.Losse R.Muminovic A.Brunn W.Nitsche M. R.Bothien J. P.Moeck C. O.Paschereit B. R.Noack U.Rist M.Zengl inproceedings Lacarelle2008a 2008 Volume 3: Combustion, Fuels and Emissions, Parts A and B Paper no. GT2008-50970 735-748 Proc. of GT2008, ASME Turbo Expo 2008: Power for Land, Sea and Air, 9-13 June 2008, Berlin, Germany 978-0-7918-4313-0 10.1115/gt2008-50970 A.Lacarelle T.Faustmann D.Greenblatt C. O.Paschereit O.Lehmann D. M.Luchtenburg B. R.Noack inproceedings Moeck2008 2008 paper no. 2008-2946 Proc. 14th AIAA/CEAS Aeroacoustics Conference, 5-7 May 2008, Vancouver, Canada 1-56347-939-7 J. P.Moeck M. R.Bothien S.Schimek A.Lacarelle C. O.Paschereit inproceedings Seele2008 2008 Proceedings of 2nd International Conference on Jets, Wakes and Separated Flows (ICJWSF), Berlin, Germany R.Seele K.Oberleithner C. O.Paschereit I.Wygnanski inproceedings Oberleithner2008 2008 Proceedings of 2nd International Conference on Jets, Wakes and Separated Flows (ICJWSF), Berlin, Germany K.Oberleithner C. O.Paschereit I.Wygnanski article Guyot2007 Proceedings in Applied Mathematics and Mechanics (PAMM) 2007 7 1 4090015-4090016 10.1002/pamm.200700715 D.Guyot M. R.Bothien J. P.Moeck C. O.Paschereit article Greenblatt2007 Notes on Numerical Fluid Mechanics and Multidisciplinary Design 2007 95 281-292 978-3-540-71438-5 D.Greenblatt Y.Kastantin Y.Singh C. N.Nayeri C. O.Paschereit article Bothien2007b Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 2007 221 5 657-668 Professional Engineering 0957-6509 (Print) 2041-2967 (Onl 10.1243/09576509jpe384 M. R.Bothien J. P.Moeck A.Lacarelle C. O.Paschereit inproceedings Guyot2007a 2007 CD-ROM/DVD 14th International Congress on Sound and Vibration, Cairns, Australia, 2007 978-0-733-42516-5 D.Guyot M.Roessler M. R.Bothien C. O.Paschereit inproceedings Moeck2007 2007 AIAA paper no. 2007-3540 13th AIAA/CEAS Aeroacoustics Conference (28th AIAA Aeroacoustics Conference), May 21-23, 2007, Rome, Italy J. P.Moeck M. R.Bothien C. O.Paschereit inproceedings Moeck2007a 2007 Proceedings of the 14th International Congress on Sound and Vibration, 9-12 July 2007, Cairns, Australia 978-0-733-42516-5 J. P.Moeck H. J.Konle C. O.Paschereit inproceedings Moeck2007b 2007 Proceedings of the 14th International Congress on Sound and Vibration, 9-12 July 2007, Cairns, Australia 978-0-733-42516-5 J. P.Moeck H.-J.Schmidt M.Oevermann C. O.Paschereit R.Klein inproceedings Gutmark2007 2007 AIAA paper no. 2007-3697 13th AIAA/CEAS Aeroacoustics Conference (28th AIAA Aeroacoustics Conference), May 21-23, 2007, Rome, Italy E. J.Gutmark C. O.Paschereit D.Guyot A.Lacarelle J. P.Moeck S.Schimek T.Faustmann M. R.Bothien inproceedings Greenblatt2007a 2007 AIAA paper no. 2007-4277 AIAA 25th AIAA Applied Aerodynamics Conference, 25-28 June, Miami, FL D.Greenblatt Y.Kastantin C. N.Nayeri C. O.Paschereit inproceedings Lacarelle2007 2007 AIAA paper no. 2007-1417 45th AIAA Aerospace Sciences Meeting and Exhibit, Jan. 8-11, 2007, Reno, Nevada, USA A.Lacarelle J. P.Moeck H. J.Konle S.Vey C. N.Nayeri C. O.Paschereit inproceedings Bothien2007 2007 Proceedings of the 14th International Congress on Sound and Vibration, Cairns, Australia 978-0-733-42516-5 M. R.Bothien J. P.Moeck C. O.Paschereit inproceedings Pfeifer2007 2007 11th CEAS/ASC Workshop of X3-Noise, 27/28 September, 2007, Istituto Superior Tecnico, Lisbon C.Pfeifer J. P.Moeck C. O.Paschereit L.Enghardt inproceedings Bothien2007a 2007 Volume 2: Turbo Expo 2007 ASME paper GT2007-27796 607-617 ASME Turbo Expo 2007: Power for Land, Sea, and Air (GT2007), May 14-17, 2007 , Montreal, Canada 0-7918-4791-8 10.1115/gt2007-27796 M. R.Bothien J. P.Moeck C. O.Paschereit inproceedings Albrecht2007 2007 AIAA paper no. 2007-5632 43rd AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, July 8-11, 2007, Cincinnati, OH, USA 1492-955909 P.Albrecht S.Speck S.Schimek F.Bauermeister C. O.Paschereit E. J.Gutmark inproceedings Paschereit2007 2007 20 638 Bundesministerium für Verkehr, Bau und Stadtentwicklung Verkehrsblatt-Verlag, Bonn Verkehrsblatt 0042-4013 C. O.Paschereit J. P.Moeck R.Engel inproceedings Moeck2007c 2007 Proceedings of the 14th International Congress on Sound and Vibration, Cairns, Australia 978-0-733-42516-5 J. P.Moeck R.Engel C. O.Paschereit inproceedings Moeck2007d Notes on Numerical Fluid Mechanics and Multidisciplinary Design (NNFM) 2007 95 Papers contributed to the 1st Conference on "Active Flow Control", Sep. 27-29, 2006, Berlin, Germany 408--421 King, R. Springer-Verlag Berlin Notes on Numerical Fluid Mechanics and Multidisciplinary Design (NNFM) 978-3-540-71438-5 und 3-540-7143 10.1007/978-3-540-71439-2 J. P.Moeck M. R.Bothien D.Guyot C. O.Paschereit inproceedings Guyot2007b 2007 AIAA paper no. 2007-5630 43rd AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, July 8-11, 2007, Cincinnati, OH, USA D.Guyot M. R.Bothien J. P.Moeck A.Lacarelle S.Schimek T.Faustmann C. O.Paschereit E. J.Gutmark inproceedings Goeksel2007 2007 95 Papers contributed to the 1st Conference on "Active Flow Control", Sep. 27-29, 2006, Berlin, Germany 42-55 King, R. Springer Verlag, Berlin Notes on Numerical Fluid Mechanics and Multidisciplinary Design (NNFM) 978-3-540-71438-5 und 3-540-7143 10.1007/978-3-540-71439-2 B.Göksel D.Greenblatt I.Rechenberg Y.Kastantin C. N.Nayeri C. O.Paschereit inproceedings Moeck2007e 2007 AIAA paper no. 2007-1416 Proc. 45th AIAA Aerospace Sciences Meeting and Exhibit, January 8-11, 2007, Reno, Nevada, USA J. P.Moeck M. R.Bothien C. O.Paschereit G.Gelbert R.King inproceedings Oberleithner2007a 2007 5010 http://hdl.handle.net/2042/15578 AFM, Maison de la Mécanique, 39/41 rue Louis Blanc - 92400 Courbevoie 18eme Congres Francais de Mécanique, 27-31 Août 2007, Grenoble, Colloquium C3: Stratified and Rotating Flows K.Oberleithner C. O.Paschereit I.Wygnanski article Paschereit2006 Journal of Turbomachinery 2006 128 4 679-688 C. O.Paschereit P.Flohr E. J.Gutmark article Paschereit2006a AIAA Journal 2006 44 3 550-557 C. O.Paschereit E. J.Gutmark inproceedings Bothien2006 2006 Proceedings of the 13th International Conference on Modelling Fluid Flow, Budapest, Hungary M. R.Bothien J. P.Moeck C. O.Paschereit inproceedings Greenblatt2006 2006 First Berlin Conference on Active Flow Control, Berlin, Germany D.Greenblatt Y.Singh Y.Kastantin C. N.Nayeri C. O.Paschereit inproceedings Albrecht2006 2006 Volume 1: Combustion and Fuels, Education ASME paper GT2006-90340 293-302 ASME Turbo Expo 2006: Power for Land, Sea, and Air (GT2006), May 8-11, 2006 , Barcelona, Spain 0-7918-4236-3 10.1115/gt2006-90340 P.Albrecht F.Bauermeister M. R.Bothien A.Lacarelle J. P.Moeck C. O.Paschereit E. J.Gutmark inproceedings Paschereit2006b 2006 Proc. Symposium in honor of Prof. I. Wygnanski, June 14-17, 2006, Eilat, Israel C. O.Paschereit inproceedings Schuermans2006 2006 44th AIAA Aerospace Sciences Meeting and Exhibit, January 9-12, 2006, Reno, NV, USA B.Schuermans C. O.Paschereit P.Monkewitz inproceedings Goeksel2006 2006 Proc. Symposium in honor of Professor I. Wygnanski, June 14-17, 2006, Eilat, Israel B.Göksel D.Greenblatt C. N.Nayeri C. O.Paschereit inproceedings Goeksel2006a 2006 Proc. Turbulence and Interactions TI2006, May 29 - June 2, 2006, Porquerolles, France B.Göksel D.Greenblatt I.Rechenberg Y.Singh C. N.Nayeri C. O.Paschereit inproceedings Paschereit2006c 2006 Vienna, Austria Proceedings of the 13th International Congress on Sound and Vibration, July 2-6, 2006, Vienna, Austria C. O.Paschereit J. P.Moeck M. R.Bothien inproceedings Goeksel2006b 2006 AIAA paper no. 2006-3686 3rd AIAA Flow Control Conference, June 5-8, 2006, San Francisco, CA, USA B.Göksel D.Greenblatt I.Rechenberg C. N.Nayeri C. O.Paschereit techreport Nayeri2006 2006 STAB Jahresbericht C. N.Nayeri O.Zühlke L.Löfdahl C. O.Paschereit unpublished Greenblatt2006a 2006 1st Conference on "Active Flow Control", Sep. 27-29, 2006, Berlin, Germany D.Greenblatt Y.Kastantin Y.Singh C. N.Nayeri C. O.Paschereit article Bellucci2005 Journal of Turbomachinery 2005 127 2 372-379 V.Bellucci B.Schuermans D.Nowak P.Flohr C. O.Paschereit inbook Paschereit2005 2005 210 445-479 Lieuwen, T. C. and Yang, V. Published by AIAA Progress in Astronautics and Aeronautics Implementation of instability prediction in design: ALSTOM approaches C. O.Paschereit B.Schuermans V.Bellucci P.Flohr inproceedings Sonnenberger2005 2005 Proc. of the International Conference on Jets, Wakes and Separated Flows, Oct. 5-8, 2005, Mie, Japan R.Sonnenberger C. N.Nayeri H. H.Fernholz C. O.Paschereit inproceedings Paschereit2005a 2005 Proc. of the Twelth International Congress on Sound and Vibration, July 11-14, 2005, Instituto Superior Técnico, Lisbon, Portugal. C. O.Paschereit E. J.Gutmark inproceedings Paschereit2005b 2005 Proc. of the International Conference on Jets, Wakes and Separated Flows, Oct. 5-8, 2005, Mie, Japan C. O.Paschereit B.Schuermans inproceedings Paschereit2005c 2005 Proc. of the Twelth International Congress on Sound and Vibration, July 11-14, 2005, Instituto Superior Técnico, Lisbon, Portugal. C. O.Paschereit B.Schuermans V.Bellucci article Bellucci2004 AIAA Journal 2004 42 8 1543-1549 V.Bellucci C. O.Paschereit P.Flohr inproceedings Schuermans2004 2004 2004-GT-53831 ASME Turbo Expo, June 14-17, 2004, Vienna, Austria B.Schuermans V.Bellucci F.Güthe P.Flohr C. O.Paschereit inproceedings Sonnenberger2004 2004 X 713-716 Andersson, H. I. and Krogstad, P. A. Advances in Turbulence R.Sonnenberger H. H.Fernholz C. O.Paschereit inproceedings Paschereit2004 2004 42nd AIAA Aerospace Sciences Meeting and Exhibit, January 5-8, 2004, Reno, Nevada, USA C. O.Paschereit E. J.Gutmark inproceedings Sonnenberger2004a 2004 10th European Turbulence Conference (ETC10), June 29-July 2, 2004, Norwegian University of Science and Technology, Trondheim, Norway R.Sonnenberger H. H.Fernholz C. O.Paschereit inproceedings Flohr2004 2004 Proc. of CHT-04, International Symposium on Advances in Computational Heat Transfer, CHT-04-233, April 19-24, 2004, Norway P.Flohr C. O.Paschereit inproceedings Paschereit2004a 2004 2004-GT-53587 ASME Turbo Expo, June 14-17, 2004, Vienna, Austria C. O.Paschereit E. J.Gutmark inproceedings Schuermans2004a 2004 AIAA paper no. 2004-456 42nd AIAA Aerospace Sciences Meeting and Exhibit, January 5-8, 2004, Reno, Nevada, USA B.Schuermans V.Bellucci C. O.Paschereit P.Flohr article Campos-Delgado2003 Transactions on Control Systems Technology 2003 11 4 429-447 D. U.Campos-Delgado B.Schuermans K.Zhou C. O.Paschereit E.Gallestey A.Poncet inproceedings Paschereit2003 2003 Conference on Modelling Fluid Flow (CMFF'03) The 12th International Conference on Fluid Flow Technologies, September 3-6, 2003, Budapest, Hungary C. O.Paschereit B.Schuermans V.Bellucci inproceedings Paschereit2003a 2003 2003-GT-38393 ASME Turbo Expo, June 16-19, 2003, Atlanta, USA C. O.Paschereit B.Schuermans D.Büche inproceedings Paschereit2003b 2003 41st AIAA Aerospace Sciences Meeting and Exhibit, January 6-9, 2003, Reno, Nevada, USA C. O.Paschereit E. J.Gutmark inproceedings Flohr2003 2003 41st AIAA Aerospace Sciences Meeting and Exhibit, January 6-9, 2003, Reno, Nevada, USA P.Flohr C. O.Paschereit V.Bellucci inproceedings Schuermans2003 2003 2003-GT-38688 ASME Turbo Expo, June 16-19, 2003, Atlanta, Georgia, USA B.Schuermans V.Bellucci C. O.Paschereit article Paschereit2002b Journal of Engineering for Gas Turbines and Power 2002 3 26 124 2 239-247 0742-4795 (online), 1528-8919 (print) 10.1115/1.1383255 C. O.Paschereit B.Schuermans W.Polifke O.Mattson article Paschereit2002f Journal of Propulsion and Power 2002 18 6 1298-1304 C. O.Paschereit E. J.Gutmark inproceedings Paschereit2002 2002 2002-GT-30462 ASME Turbo Expo, June 3-6, 2002, Amsterdam, Netherlands C. O.Paschereit P.Flohr H.Knöpfel W.Geng C.Steinbach P.Stuber K.Bengtsson E. J.Gutmark inproceedings Paschereit2002a 2002 29 1 123-129 Proc. of the Combustions Institute C. O.Paschereit E. J.Gutmark inproceedings Flohr2002 2002 Proc. of IMECE, New Orleans, LA, USA P.Flohr P.Schmitt C. O.Paschereit inproceedings Flohr2002a 2002 ASME International Mechanical Engineering Congress and Exposition, Symposium on Computational Modeling of Industrial Combustion Systems, November 17-22, 2002, New Orleans, LO P.Flohr C. O.Paschereit inproceedings Bellucci2002 2002 ASME Turbo Expo, June 3-6, 2002, Amsterdam, Netherlands. V.Bellucci C. O.Paschereit D.Tabacco P.Flohr inproceedings Nowak2002 2002 The 2002 International Congress and Exposition on Noise Control Engineering, August 19-21, 2002, Dearborn, MI, USA D.Nowak C. O.Paschereit inproceedings Paschereit2002c 2002 40th AIAA Aerospace Sciences Meeting and Exhibit, January 14-17, 2002, Reno, Nevada, USA C. O.Paschereit E. J.Gutmark inproceedings Paschereit2002d 2002 9th European Turbulence Conference (ETC9), July 2-5, 2002, University of Southampton, Southampton, UK. C. O.Paschereit E. J.Gutmark inproceedings Paschereit2002e 2002 9th International Congress on Sound and Vibration (ICSV9), July 8-11, 2002, Orlando, FL, USA C. O.Paschereit inproceedings Paschereit2002g 2002 The International Council of the Aeronautical Sciences (ICAS), 23rd Congress of ICAS, September 8-13, 2002, Toronto, Canada. C. O.Paschereit E. J.Gutmark inproceedings Paschereit2002h 2002 ASME Turbo Expo, June 3-6, 2002, Amsterdam, Netherlands C. O.Paschereit article Polifke2001 International Journal of Acoustics and Vibration 2001 6 3 135-146 W.Polifke C. O.Paschereit K.Döbbeling article Polifke2001a Journal of Sound and Vibration 2001 245 3 483-510 W.Polifke A.Poncet C. O.Paschereit K.Döbbeling inproceedings Paschereit2001 2001 39th AIAA Aerospace Science Meeting and Exhibit, January 8-11, 2001, Reno, Nevada, USA C. O.Paschereit B.Schuermans D. U.Campos-Delgado inproceedings Paschereit2001a 2001 invited paper, Verbrennungsschwingungen - Thermoakustik, November 13, 2001, Universität der Bundeswehr, Hamburg, Haus der Technik E.V. C. O.Paschereit inproceedings Paschereit2001b 2001 39th AIAA Aerospace Science Meeting and Exhibit, January 8-11, 2001, Reno, Nevada, USA C. O.Paschereit B.Schuermans D. U.Campos-Delgado inproceedings Paschereit2001c 2001 39th AIAA Aerospace Science Meeting and Exhibit, January 8-11, 2001, Reno, Nevada, USA C. O.Paschereit P.Flohr B.Schuermans inproceedings Bellucci2001 2001 ASME Turbo Expo, June 4-6, 2001, New Orleans, Louisiana, USA V.Bellucci C. O.Paschereit P.Flohr F.Magni inproceedings Paschereit2001d 2001 AIAA paper no. 2001-484 39th AIAA Aerospace Science Meeting and Exhibit, January 8-11, 2001, Reno, Nevada, USA C. O.Paschereit P.Flohr B.Schuermans inproceedings Bellucci2001a 2001 AIAA paper no. 2001-2794 31st AIAA Fluid Dynamics Conference (Aeroacoustics Section), June 11-14, 2001, Anaheim, California, USA V.Bellucci C. O.Paschereit P.Flohr B.Schuermans inproceedings Flohr2001 2001 ASME Turbo Expo, June 4-6, 2001, New Orleans, Louisiana P.Flohr C. O.Paschereit B.van Roon article Paschereit2000a AIAA Journal 2000 38 1025-1034 C. O.Paschereit E. J.Gutmark W.Weisenstein inproceedings Paschereit2000 2000 Topic Oriented Meeting "Intelligent Combustion Control" of the International Flame Research Foundation, September 25-27, 2000, Paris, France C. O.Paschereit E. J.Gutmark inproceedings Paschereit2000b 2000 Ziada, Staubli, Flow Induced Vibrations, Balkema C. O.Paschereit P.Flohr W.Polifke M.Bockholts inproceedings Paschereit2000c 2000 VIII 101-104 Dopazo, C. Proceedings of the 8th European Turbulence Conference, Barcelona, Spain 27-30 June 2000 Advances in Turbulence C. O.Paschereit E. J.Gutmark L.Haber inproceedings Schuermans2000 2000 Acoustics of combustion EUROTHERM Seminar No. 67, July 5-7, 2000, Univ of Twente, Enschede, The Netherlands B.Schuermans C. O.Paschereit inproceedings Gutmark2000 2000 Bulletin of the American Physical Society / Division of Fluid Dynamics, Annual Meeting, November 19-21, 2000, Washington, DC, USA E. J.Gutmark C. O.Paschereit inproceedings Paschereit2000d 2000 6th AIAA/CEAS Aeroacoustics Conference, June 12-14, 2000, Maui, Hawaii C. O.Paschereit P.Flohr E. J.Gutmark L.Haber inproceedings Paschereit2000e 2000 Applied vehicle technology panel symposium on active control technology for enhanced performance operation capabilities of military aircraft, land vehicles and sea vehicles, North Atlantic Treaty, May 8-11, 2000, Braunschweig, Germany C. O.Paschereit E. J.Gutmark B.Schuermans inproceedings Schuermans2000a 2000 ASME Turbo Expo, May 13-16, 2000, Munich, Germany B.Schuermans W.Polifke C. O.Paschereit J.van der Linden inproceedings Schuermans2000b 2000 ASME Turbo Expo, May 13-16, 2000, Munich, Germany B.Schuermans W.Polifke C. O.Paschereit inproceedings Paschereit2000f 2000 38th AIAA Aerospace Science Meeting and Exhibit, January 11-14, 2000, Reno, Nevada C. O.Paschereit E. J.Gutmark W.Weisenstein inproceedings Paschereit2000g 2000 Proc. of the Workshop on Combustion Instabilities, December 2000, Moscow, Russia C. O.Paschereit article Paschereit1999a Physics of Fluids 1999 9 2667-2678 C. O.Paschereit E. J.Gutmark W.Weisenstein inproceedings Paschereit1999 1999 14th International Symposium on Airbreathing EnginesSeptember 5-10, 1999, Florence, Italy C. O.Paschereit E. J.Gutmark W.Weisenstein inproceedings Paschereit1999b 1999 17th International Colloquium on the Dynamics of Explosions and Reactive Systems, July 25-30, 1999, Heidelberg, Germany C. O.Paschereit E. J.Gutmark W.Weisenstein inproceedings Paschereit1999c 1999 ASME Turbo Expo, June 7-10, 1999, Indianapolis, Indiana, USA, C. O.Paschereit E. J.Gutmark W.Weisenstein inproceedings Paschereit1999d 1999 AIAA paper no. 99-0711 37th AIAA Aerospace Science Meeting and Exhibit, January 11-14, 1999, Reno, Nevada C. O.Paschereit E. J.Gutmark W.Weisenstein inproceedings Paschereit1999e 1999 ASME Turbo Expo, June 7-10, 1999, Indianapolis, Indiana, USA C. O.Paschereit B.Schuermans W.Polifke O.Mattson inproceedings Schuermans1999 1999 ASME Turbo Expo, June 7-10, 1999, Indianapolis, Indiana, USA B.Schuermans C. O.Paschereit W.Polifke inproceedings Paschereit1999f 1999 Bulletin of the American Physical Society / Division of Fluid Dynamics, Annual Meeting, New Orleans, Louisiana, USA C. O.Paschereit E. J.Gutmark W.Weisenstein inproceedings Gutmark1999 1999 Bulletin of the American Physical Society / Division of Fluid Dynamics, Annual Meeting, New Orleans, Louisiana, USA E. J.Gutmark C. O.Paschereit W.Weisenstein inproceedings Gutmark1999a 1999 Sixth International Congress on Sound and Vibration, July 5-8, Lyngby, Denmark E. J.Gutmark C. O.Paschereit W.Weisenstein inproceedings Paschereit1999g 1999 5th AIAA/CEAS Aeroacoustics Conference, May 10-12, Seattle, WA, USA C. O.Paschereit E. J.Gutmark W.Weisenstein inproceedings Polifke1999 1999 Sixth International Congress on Sound and Vibration, July 5-8, 1999, Lyngby, Denmark W.Polifke C. O.Paschereit K.Döbbeling article Paschereit1998a Proceedings of the Combustion Institute 1998 27 1817-1824 C. O.Paschereit E. J.Gutmark W.Weisenstein article Polifke1998 ERCOFTAC Bulletin 1998 38 W.Polifke C. O.Paschereit article Paschereit1998f Combustion Science and Technology 1998 138 213-232 http://www.informaworld.com/smpp/ftinterface~content=a777336112~fulltext=713240930~frm=content 10.1080/00102209808952069 C. O.Paschereit E. J.Gutmark W.Weisenstein article Fiedler1998 Experimental Thermal and Fluid Science 1998 16 3-21 10.1016/s0894-1777(97)10003-6 H. E.Fiedler C. N.Nayeri R.Spieweg C. O.Paschereit inproceedings Paschereit1998 1998 Proc. of the IEEE International Conference on Control Applications, September 1-4, 1998 C. O.Paschereit E. J.Gutmark W.Weisenstein inproceedings Paschereit1998b 1998 AIAA paper no. 98-2274 4th AIAA/ CEAS Aeroacoustics Conference, June 2-4, 1998, Toulouse, France C. O.Paschereit E. J.Gutmark W.Weisenstein inproceedings Paschereit1998c 1998 ASME Paper 98-GT-582 ASME Turbo Expo, June 2-5, 1998, Stockholm, Sweden C. O.Paschereit W.Polifke inproceedings Paschereit1998d 1998 AIAA paper no. 98-2433 29th AIAA Fluid Dynamics Conference, June 15-18, 1998, Albuquerque, New-Mexico C. O.Paschereit E. J.Gutmark W.Weisenstein inproceedings Paschereit1998e 1998 AIAA paper no. 98-1067 36th AIAA Aerospace Science Meeting and Exhibit, January 12-15, 1998, Reno, Nevada C. O.Paschereit E. J.Gutmark W.Weisenstein inproceedings Paschereit1998g 1998 VII 293-296 Frisch, U. Kluwer Academics, Dordrecht/ Boston/ London Advances in Turbulence C. O.Paschereit E. J.Gutmark W.Weisenstein inproceedings Gutmark1997 1997 Bulletin of the American Physical Society/ Division of Fluid Dynamics, Annual Meeting, San Francisco, California, USA E. J.Gutmark C. O.Paschereit W.Weisenstein B.Paikert inproceedings Paschereit1997 1997 Bulletin of the American Physical Society/ Division of Fluid Dynamics, Annual Meeting, San Francisco, California, USA C. O.Paschereit W.Polifke techreport Polifke1997 1997 1313 455-460 VDI-Bericht W.Polifke C. O.Paschereit T.Sattelmayer article Paschereit1995a Journal of Fluid Mechanics 1995 283 365-407 C. O.Paschereit I.Wygnanski H. E.Fiedler techreport Paschereit1995 1995 DFG-Bericht C. O.Paschereit inproceedings Paschereit1994a 1994 Proc. of the International Conference on Railway Research C. O.Paschereit B.Barsikow techreport Paschereit1994 1994 Technical Report, akustik data, October 1994, Paris, France C. O.Paschereit inbook Paschereit1993 1993 149 53-64 Branover, H. and Mond, M. and Unger, Y. Published by AIAA Progress in Astronautics and Aeronautics On instabilities in the axisymmmetric jet: Subharmonic resonance C. O.Paschereit I.Wygnanski inbook Paschereit1993a 1993 21 115-123 Bonnet, J. P. and Glauser, M. N. Kluwer Academics, Dordrecht/ Boston/ London Fluid Mechanics and its Applications On the influence of initial parameters on subharmonic resonance in an axisymmetric jet C. O.Paschereit H. E.Fiedler I.Wygnanski inproceedings Paschereit1993b 1993 Bulletin of the American Physical Society/ Division of Fluid Dynamics, 46th Annual Meeting, Albuquerque, New Mexico, USA C. O.Paschereit H. E.Fiedler article Paschereit1992 Experiments in Fluids 1992 12 3 189-199 Springer-Verlag 0723-4864 (print), 1432-1114 (online) 10.1007/BF00188258 C. O.Paschereit D.Oster T. A.Long H. E.Fiedler I.Wygnanski inproceedings Paschereit1989 1989 Bulletin of the American Physical Society/ Division of Fluid Dynamics, 42nd Annual Meeting, Palo Alto, California, USA C. O.Paschereit I.Wygnanski inproceedings Paschereit1989a 1989 2 467-471 Fernholz, H. H. and Fiedler, H. E. Springer Verlag, Berlin Advances in Turbulence C. O.Paschereit M.Schüttpelz H. E.Fiedler