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% sevenpack version 0.7.16
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% --- Timezone: CEST
% Creation date: 2019-09-16
% Creation time: 15-04-32
% --- Number of references
% 42
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@Article { Saverin2018,
   title = {Comparison of experimental and numerically predicted three-dimensional wake behaviour of a vertical axis wind turbine},
   journal = {Journal of Engineering Gas Turbine Power},
   year = {2018},
   month = {4},
   pages = {12},
   abstract = {The evolution of the wake of a wind turbine contributes significantly to its operation and performance, as well as to those of machines installed in the vicinity. The inherent unsteady and three-dimensional aerodynamics of Vertical Axis Wind Turbines (VAWT) have hitherto limited the research on wake evolution. In this paper the wakes of both a troposkien and a H-type VAWT rotor are investigated by comparing experiments and calculations. Experiments were carried out in the large-scale wind tunnel of the Politecnico di Milano, where unsteady velocity measurements in the wake were performed by means of hot wire anemometry. The geometry of the rotors was reconstructed in the open-source wind-turbine software QBlade, developed at the TU Berlin. The aerodynamic model makes use of a lifting line free-vortex wake (LLFVW) formulation, including an adapted Beddoes-Leishman unsteady aerodynamic model; airfoil polars are introduced to assign sectional lift and drag coefficients. A wake sensitivity analysis was carried out to maximize the reliability of wake predictions. The calculations are shown to reproduce several wake features observed in the experiments, including blade-tip vortex, dominant and submissive vortical structures, and periodic unsteadiness caused by sectional dynamic stall. The experimental assessment of the simulations illustrates that the LLFVW model is capable of predicting the unsteady wake development with very limited computational cost, thus making the model ideal for the design and optimization of VAWTs.},
   note = {GTP-17-1608},
   url = {http://gasturbinespower.asmedigitalcollection.asme.org/article.aspx?articleid=2678430},
   DOI = {10.1115/1.4039935},
   author = {Saverin, J. and Marten, D. and Holst, D. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O. and Persico, G.}
}

@Article { Eulalie2018,
   title = {Active flow control analysis at the rear of an SUV},
   journal = {International Journal of Numerical Methods for Heat \& Fluid Flow},
   year = {2018},
   abstract = {Purpose This research paper presents an experimental investigation of an active flow control solution mounted at rear of a Sport Utility vehicle (SUV) with the objective of drag reduction, thanks to a selection of flow control parameters leading to a pressure increase on the tailgate. Design/methodology/approach A flow control design of experiments was conducted with a pulsed jet system mounted on the top and sides of the rear window of the vehicle. The wall pressure, instantaneous velocity and drag were measured with this prototype in a wind tunnel. A Dynamic Modal Decomposition (DMD) analysis of the pressure enables to describe the pressure fluctuations. Fluid Dynamic Computations show relation between pressure and velocity fields. Findings Measurements with this prototype in the wind tunnel revealed small improvements in drag for the best flow control configurations. This small benefit is due to the core of the upper span wise vortex further away from the rear window than the lower span wise vortex. These small improvements in drag were confirmed with pressure measurements on the rear window and tailgate. The DMD analysis of the surface pressure showed a low frequency pendulum oscillation on the lower area of the tailgate, linked with low velocity frequencies in the shear layers near the tailgate. Originality/value Experimental and numerical results show interest to increase pressure at bottom of the rear end of this SUV prototype. The dynamic description of the wall pressure shows importance of flow control solutions reducing pressure fluctuations at low frequencies in the lower area of the tailgate.},
   url = {https://www.emeraldinsight.com/doi/abs/10.1108/HFF-06-2017-0230\#},
   ISSN = {0961-5539},
   DOI = {10.1108/hff-06-2017-0230},
   author = {Eulalie, Y. and Fournier, E. and Gilotte, Ph. and Holst, D. and Johnson, S. and Nayeri, C. N. and Sch{\"u}tz, Th. and Wieser, D.}
}

@Article { Lennie2018,
   title = {Vortex shedding and frequency lock in on stand still wind turbines, a baseline experiment},
   journal = {Journal of Engineering Gas Turbine Power},
   year = {2018},
   pages = {15},
   abstract = {During the commissioning and stand-still cycles of wind turbines, the rotor is often stopped or even locked leaving the rotor blades at a standstill. When the blades are at a stand still, angles of attack on the blades can be very high and it is therefore possible that they experience vortex induced vibrations. This experiment and analysis helps to explain the different regimes of flow at very high angles of attack, particularly on moderately twisted and tapered blades. A single blade was tested at two different flow velocities at a range of angles of attack with flow tuft visualisation and hotwire measurements of the wake. Hotwire wake measurements were able to show the gradual inception and ending of certain flow regimes. The power spectral densities of these measurements were normalized in terms of Strouhal number based on the projected chord to show that certain wake features have a relatively constant Strouhal number. The shedding frequency appears then to be relatively independent of chord taper and twist. Vortex generators were tested but were found to have little influence in this case. Gurney flaps were found to modify the wake geometry, stall onset angles and in some cases the shedding frequency.},
   note = {GTP-17-1616},
   url = {http://gasturbinespower.asmedigitalcollection.asme.org/article.aspx?articleid=2677759},
   DOI = {10.1115/1.4039818},
   author = {Lennie, M. and Selahi-Moghaddam, A. and Holst, D. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.}
}

@Proceedings { Edwige2018,
   title = {Flow Control Around a SUV Simplified Vehicle},
   journal = {ASME 2018 5th Joint US-European Fluids Engineering Division Summer Meeting},
   year = {2018},
   volume = {2 Development and Applications in Computational Fluid Dynamics; Industrial and Environmental Applications of Fluid Mechanics; Fluid Measurement and Instrumentation},
   abstract = {The research on the external aerodynamics of ground vehicles can nowadays be related to sustainable development strategies, confirmed by the worldwide CO2 regulation target. Automotive manufacturers estimate that a drag reduction of 30\% contributes to 10g/km of CO2 reduction. However, this drag reduction should be obtained without constraints on the design, the safety, comfort and habitability of the passengers. Thus, it is interesting to find flow control solutions, which will remove or remote recirculation zones due to separation edges with appropriate control techniques. In automotive sales, the SUV, 4x4 and compact cars represent a large part of the market share and the study of control approaches for this geometry is practically useful. In this work, appropriate control techniques are designed to decrease the drag forces around a reduced scale SUV car benchmark called POSUV. The control techniques are based on the DMD (Dynamic Mode Decomposition) algorithms generating an optimized drag reduction procedure. It involves independent transient inflow boundary conditions for flow control actuation in the vicinity of the separation zones and time resolved pressure sensor output signals on the rear end surface of the mockup. This study, that exploits dominant flow features behind the tailgate and the rear bumper, is performed using Large Eddy Simulations on a sufficient run time scale, in order to minimize a cost function dealing with the time and space average pressure coefficient. The resulting dynamic modal decomposition obtained by these LES simulations and by wind tunnel measurements has been compared for the reference case, in order to select the most appropriate run time scale. Analysis of the numerical results shows a significant pressure increase on the tailgate, for independent flow control frequencies. Similar decomposition performed in the wake with and without numerical flow control help understanding the flow modifications in the detachment zones.},
   note = {Montreal, Quebec, Canada, July 15-20, 2018},
   url = {http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2710650},
   series = {ASME Proceedings | 25th Symposium on Industrial and Environmental Applications of Fluid Mechanics},
   organization = {ASME},
   ISBN = {978-0-7918-5156-2},
   DOI = {10.1115/FEDSM2018-83444},
   author = {Edwige, S. and Gilotte, Ph. and Mortazavi, I. and Eulalie, Y. and Holst, D. and Nayeri, C. N. and Aider, J.-L. and Varon, E.}
}

@Inproceedings { Holst2018a,
   title = {Static and dynamic analysis of a NACA 0021 airfoil section at low Reynolds numbers based on experiments and CFD},
   year = {2018},
   month = {6},
   pages = {12},
   abstract = {The wind industry needs airfoil data for ranges of Angle of Attack (AoA) much wider than those of aviation applications, since large portions of the blades may operate in stalled conditions for a significant part of their lives. Vertical axis wind turbines (VAWTs) are even more affected by this need, since data sets across the full incidence range of 180 degree are necessary for a correct performance prediction at different tip-speed ratios. However, the relevant technical literature lacks data in deep and post stall regions for nearly every airfoil. Within this context, the present study shows experimental and numerical results for the well-known NACA 0021 airfoil, which is often used for Darrieus VAWT design. Experimental data were obtained through dedicated wind tunnel measurements of a NACA 0021 airfoil with surface pressure taps, which provided further insight into the pressure coefficient distribution across a wide range of AoAs. The measurements were conducted at two different Reynolds umbers (Re=140k and Re=180k): each experiment was performed multiple times to ensure repeatability. Dynamic AoA changes were also investigated at multiple reduced frequencies. Moreover, dedicated unsteady numerical simulations were carried out on the same airfoil shape to reproduce both the static polars of the airfoil and some relevant dynamic AoA variation cycles tested in the experiments. The solved flow fieldwas then exploited both to get further insight into the flow mechanisms highlighted by the wind tunnel tests and to provide correction factors to discard the influence of the experimental apparatus, making experiments representative of open-field behaviour. The present study is then thought to provide the scientific community with high quality, low-Reynolds airfoil data, which may enable in the near future a more effective design of Darrieus VAWTs.},
   note = {GT2018-75426},
   url = {https://www.asme.org/events/turbo-expo2018},
   publisher = {ASME},
   series = {Proceedings of ASME Turbo Expo 2018 Turbomachinery Technical Conference and Exposition},
   booktitle = {Proceedings of the ASME Turbo Expo 2018},
   organization = {ASME},
   author = {Holst, D. and Balduzzi, F. and Bianchini, A. and Church, B. and Wegner, F. and Pechlivanoglou, G. and Ferrari, L. and Ferrara, G. and Nayeri, C. N. and Paschereit, C. O.}
}

@Inproceedings { Holst2018b,
   title = {Experimental analysis of a NACA 0021 airfoil under dynamic angle of attack variation and low Reynolds numbers},
   year = {2018},
   pages = {12},
   abstract = {The wind industry needs reliable and accurate airfoil polars to properly predict wind turbine performance, especially during the initial design phase. Medium- and low-fidelity simulations directly depend on the accuracy of the airfoil data and even more so if e.g. dynamic effects are modeled. This becomes crucial if the blades of a turbine operate under stalled conditions for a significant part of the turbine's lifetime. In addition, the design process of vertical axis wind turbines (VAWTs) needs data across the full range of angles of attack between 0 and 180 deg. Lift, drag and surface pressure distributions of a NACA 0021 airfoil equipped with surface pressure taps were investigated based on time-resolved pressure measurements. The present study discusses full range static polars and several dynamic sinusoidal pitching configurations covering two Reynolds numbers Re = 140k and 180 k, and different incidence ranges: near stall, post stall and deep stall. Various bi-stable flow phenomena are discussed based on high frequency measurements revealing large lift-fluctuations in the post and deep stall regime that exceed the maximum lift of the static polars and are not captured by averaged measurements. Detailed surface pressure distributions are discussed to provide further insight into the flow conditions and pressure development during dynamic motion. The experimental data provided within the present paper is dedicated to the scientific community for calibration and reference purposes, which in the future may lead to higher accuracy in performance predictions during the design process of wind turbines.},
   note = {GT2018-76514},
   url = {https://www.asme.org/events/turbo-expo2018},
   publisher = {ASME},
   series = {Proceedings of ASME Turbo Expo 2018 Turbomachinery Technical Conference and Exposition},
   booktitle = {Proceedings of the ASME Turbo Expo 2018},
   organization = {ASME},
   author = {Holst, D. and Church, B. and Wegner, F. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.}
}

@Inbook { Menzel2017,
   title = {Visualisierungswindkanal (ViWiKa) f{\"u}r Messe, Forschung und Lehre auf Basis von myRIO-1900},
   year = {2017},
   pages = {430 - 434},
   web_url = {http://www.etz.de/files/10_02_menzel-holst-fischer.pdf},
   editor = {Rahman J., Heinze R.},
   publisher = {VDE Verlag},
   chapter = {Forschung und Lehre in Virtuelle Instrumente in der Praxis 2017},
   ISBN = {978-3-800-4441-1},
   author = {Menzel, C. and Holst, D. and Fischer, J. and Nayeri, C. N. and Paschereit, C. O.}
}

@Inproceedings { Holst2017,
   title = {Experimental Analysis of a NACA 0021 Airfoil Section Through 180-Degree Angle of Attack at Low Reynolds Numbers for Use in Wind Turbine Analysis},
   year = {2017},
   month = {6},
   day = {30},
   volume = {9},
   pages = {12},
   abstract = {Wind turbine industry has a special need for accurate post stall airfoil data. While literature often covers incidence ranges [−10deg,+25deg] smaller machines experience a range of up to 90 deg for horizontal axis and up to 360 deg for vertical axis wind turbines (VAWTs). The post stall data of airfoils is crucial to improve the prediction of the start-up behavior as well as the performance at low tip speed ratios. The present paper analyzes and discusses the performance of the symmetrical NACA 0021 airfoil at three Reynolds numbers (Re = 100k, 140k, and 180k) through 180 deg incidence. The typical problem of blockage within a wind tunnel was avoided using an open test section. The experiments were conducted in terms of surface pressure distribution over the airfoil for a tripped and a baseline configuration. The pressure was used to gain lift, pressure drag, moment data. Further investigations with positive and negative pitching revealed a second hysteresis loop in the deep post stall region resulting in a difference of 0.2 in moment coefficient and 0.5 in lift.},
   url = {http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2650571},
   publisher = {ASME},
   series = {Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy},
   booktitle = {ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition},
   organization = {ASME},
   event_place = {Charlotte, North Carolina, USA},
   event_name = {ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition},
   event_date = {26 - 30 Juni 2017},
   language = {English},
   ISBN = {ISBN: 978-0-7918-5096-1},
   DOI = {10.1115/GT2017-63643},
   author = {Holst, D. and Church, B. and Pechlivanoglou, G. and T{\"u}z {\"U}ner, E. and Saverin, J. and Nayeri, C. N. and Paschereit, C. O.}
}

@Inproceedings { Holst2017a,
   title = {Comparison of Experimental and Numerically Predicted Three-Dimensional Wake Behaviour of a Vertical Axis Wind Turbine},
   year = {2017},
   month = {6},
   volume = {9},
   abstract = {The evolution of the wake of a wind turbine contributes significantly to its operation and performance, as well as to those of machines installed in the vicinity. The inherent unsteady and three-dimensional aerodynamics of Vertical Axis Wind Turbines (VAWT) have hitherto limited the research on wake evolution. In this paper the wakes of both a troposkien and a H-type VAWT rotor are investigated by comparing experiments and calculations. Experiments were carried out in the large-scale wind tunnel of the Politecnico di Milano, where unsteady velocity measurements in the wake were performed by means of hot wire anemometry. The geometry of the rotors was reconstructed in the open-source wind-turbine software QBlade, developed at the TU Berlin. The aerodynamic model makes use of a lifting line free-vortex wake (LLFVW) formulation, including an adapted Beddoes-Leishman unsteady aerodynamic model; airfoil polars are introduced to assign sectional lift and drag coefficients. A wake sensitivity analysis was carried out to maximize the reliability of wake predictions. The calculations are shown to reproduce several wake features observed in the experiments, including blade-tip vortex, dominant and submissive vortical structures, and periodic unsteadiness caused by sectional dynamic stall. The experimental assessment of the simulations illustrates that the LLFVW model is capable of predicting the unsteady wake development with very limited computational cost, thus making the model ideal for the design and optimization of VAWTs.},
   url = {http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2650574},
   publisher = {ASME},
   series = {Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy},
   booktitle = {ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition},
   organization = {ASME},
   event_place = {Charlotte, North Carolina, USA},
   event_name = {ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition},
   event_date = {26 - 30 Juni 2017},
   language = {English},
   ISBN = {ISBN: 978-0-7918-5096-1},
   DOI = {10.1115/GT2017-64004},
   author = {Saverin, J. and Marten, D. and Holst, D. and Pechlivanloglou, G. and Nayeri, C. N. and Paschereit, C. O.}
}

@Inproceedings { Holst2017b,
   title = {Vortex Shedding and Frequency Lock in on Stand Still Wind Turbines: A Baseline Experiment},
   year = {2017},
   month = {6},
   volume = {9},
   pages = {17},
   abstract = {During the commissioning and stand-still cycles of wind turbines, the rotor is often stopped or even locked leaving the rotor blades at a standstill. When the blades are at a stand still, angles of attack on the blades can be very high and it is therefore possible that they experience vortex induced vibrations. This experiment and analysis helps to explain the different regimes of flow at very high angles of attack, particularly on moderately twisted and tapered blades. A single blade was tested at two different flow velocities at a range of angles of attack with flow tuft visualisation and hotwire measurements of the wake. Hotwire wake measurements were able to show the gradual inception and ending of certain flow regimes. The power spectral densities of these measurements were normalized in terms of Strouhal number based on the projected chord to show that certain wake features have a relatively constant Strouhal number. The shedding frequency appears then to be relatively independent of chord taper and twist. Vortex generators were tested but were found to have little influence in this case. Gurney flaps were found to modify the wake geometry, stall onset angles and in some cases the shedding frequency.},
   url = {http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2650572},
   publisher = {ASME},
   series = {Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy},
   booktitle = {ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition},
   organization = {ASME},
   event_place = {Charlotte, North Carolina, USA},
   event_name = {ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition},
   event_date = {26 - 30 Juni 2017},
   language = {English},
   DOI = {0.1115/GT2017-63653},
   author = {Lennie, M. and Selahi-Moghaddam, A. and Holst, D. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.}
}

@Article { Grewe2016,
   title = {Assessing the climate impact of the AHEAD multi-fuel blended wing body},
   journal = {Meteorologische Zeitschrift},
   year = {2016},
   month = {10},
   volume = {139},
   pages = {1 - 15},
   abstract = {Air traffic is important to our society and guarantees mobility especially for long distances. Air traffic is also contributing to climate warming via emissions of CO2 and various non-CO2 effects, such as contrail-cirrus or increase in ozone concentrations. Here we investigate the climate impact of a future aircraft design, a multi fuel blended wing body (MF-BWB), conceptually designed within the EU-project AHEAD. We re-calculate the parameters for the contrail formation criterion, since this aircraft has very different characteristics compared to conventional technologies and show that contrail formation potentially already occurs at lower altitudes than for conventional aircraft. The geometry of the contrails, however, is similar to conventional aircraft, as detailed LES simulations show. The global contrail-cirrus coverage and related radiative forcing is investigated with a climate model including a contrail-cirrus parameterisation and shows an increase in contrail-cirrus radiative forcing compared to conventional technologies, if the number of emitted particles is equal to conventional technologies. However, there are strong indications that the AHEAD engines would have a substantial reduction in the emission of soot particles and there are strong indications that this leads to a substantial reduction in the contrail-cirrus radiative forcing. An overall climate impact assessment with a climate-chemistry response model shows that the climate impact is likely to be reduced by 20 \% to 25 \% compared to a future aircraft with conventional technologies. We further tested the sensitivity of this result with respect to different future scenarios for the use of bio fuels, improvements of the fuel efficiency for conventional aircraft and the impact of the number of emitted soot particles on the radiative forcing. Only the latter has the potential to significantly impact our findings and needs further investigation. Our findings show that the development of new and climate compatible aircraft designs requires the inclusion of climate impact assessments already at an early stage, i.e. pre-design level.},
   note = {Online ver{\"o}ffentlicht: Oct 14, 2016
Manuskript akzeptiert: Jun 22, 2016
Manuskript-Revision erhalten: Jun 16, 2016
Manuskript-Revision angefordert: Jan 2, 2014
Manuskript erhalten: Nov 18, 2015},
   keywords = {AHEAD project • Multi fuel blended wing body • contrails • climate impact • air traffic},
   url = {http://www.schweizerbart.de/papers/metz/detail/prepub/87038/Assessing_the_climate_impact_of_the_AHEAD_multi_fuel_blended_wing_body},
   publisher = {Schweizerbart Science Publishers},
   address = {Stuttgart, Germany},
   howpublished = {online Oct 14, 2016},
   DOI = {10.1127/metz/2016/0758},
   author = {Grewe, V. and Bock, L. and Burkhardt, U. and Dahlmann, K. and Gierens, K. and H{\"u}ttenhofer, L. and Unterstrasser, S. and Rao, A. G. and Bhat, A. and Yin, F. and Reichel, T. G. and Paschereit, C. O. and Leshayahou, Y.}
}

@Article { Holst_2016,
   title = {Potential of Retrofit Passive Flow Control for Small Horizontal Axis Wind Turbines},
   journal = {Journal of Engineering for Gas Turbines and Power},
   year = {2016},
   volume = {139},
   number = {6},
   pages = {032604-1 - 032604-8},
   abstract = {The present paper analyzes the effect of passive flow control (PFC) with respect to the retrofitting on small horizontal axis wind turbines (sHAWTs). We conducted extensive wind tunnel studies on a high performance low Reynolds airfoil using different PFC elements, i.e., vortex generators (VGs) and Gurney flaps (GF). qblade, an open source blade element momentum (BEM) code, is used to study the retrofitting potential of a simulated small wind turbine. The turbine design is presented and discussed. The simulations include the data and polars gained from the experiments and give further insight into the effects of PFC on sHAWTs. Therefore, several different blades were simulated using several variations of VG positions. This paper discusses their influence on the turbine performance. The authors especially focus on the startup performance as well as achieving increased power output at lower wind speeds. The vortex generators reduce the risk of laminar separation and enhance the lift in some configurations by more than 40 \% at low Reynolds numbers.},
   url = {http://gasturbinespower.asmedigitalcollection.asme.org/article.aspx?articleid=2547692},
   ISSN = {0742-4795},
   DOI = {10.1115/1.4034543},
   author = {Holst, D. and Pechlivanoglou, G. and Wegner, F. and Nayeri, C. N. and Paschereit, C. O.}
}

@Inbook { Holst2016c,
   title = {Entwicklung eines aerodynamischen Pr{\"u}fstands zur Fl{\"u}gelprofiluntersuchung von Kleinwindkraftanlagen unter dynamischen Winkel{\"a}nderungen auf Basis eines cRiO-9068},
   year = {2016},
   pages = {54 - 57},
   url = {http://sine.ni.com/cs/app/doc/p/id/cs-17418},
   editor = {Rahman J., Heinze R.,},
   publisher = {VDE Verlag},
   edition = {Begleitband zum 21. VIP-Kongress},
   chapter = {Mess-, Pr{\"u}f- und Regelungstechnik in Virtuelle Instrumente in der Praxis 2016},
   ISBN = {978-3-8007-4441-1},
   author = {Holst, D. and Thommes, K. and Sch{\"o}nlau, M. and Nayeri, C. N. and Paschereit, C. O.}
}

@Inproceedings { Holst2016a,
   title = {Potential of Retrofit Passive Flow Control for Small Horizontal Axis Wind Turbines},
   year = {2016},
   volume = {9},
   pages = {11},
   abstract = {The present paper analyzes the effect of passive flow control (PFC) with respect to the retrofitting on small horizontal axis wind turbines (sHAWT). We conducted extensive wind tunnel studies on an high performance low Reynolds airfoil using different PFC elements, i.e. vortex generators (VGs) and Gurney flaps. QBlade, an open source Blade Element Momentum (BEM) code, is used to study the retrofitting potential of a simulated small wind turbine. The turbine design is presented and discussed. The simulations include the data and polars gained from the experiments and give further insight into the effects of PFC on sHAWT. Therefore several different blades were simulated using several variations of VG positions. This paper discusses their influence on the turbine performance. The authors focus especially on the start-up performance as well as achieving increased power output at lower wind speeds. The vortex generators reduce the risk of laminar separation and enhance the lift in some configurations by more than 40\% at low Reynolds numbers.},
   note = {Paper No. GT2016-56679},
   publisher = {ASME},
   series = {Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy},
   booktitle = {ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy},
   DOI = {10.1115/GT2016-56679},
   author = {Holst, D. and Pechlivanoglou, G. and Wegner, F. and Nayeri, C. N. and Paschereit, C. O.}
}

@Inproceedings { Host2016b,
   title = {sHAWT Design: Airfoil Aerodynamics Under the Influence of Roughness},
   year = {2016},
   volume = {9},
   pages = {10},
   abstract = {Small horizontal axis wind turbines (sHAWTs) are mostly designed by smaller companies with no or just small possibilities of aerodynamic testing and hence, airfoil selection is often based on published performance data and minimal or no experimental testing from the blade designer's side. This paper focuses on the aerodynamic consequences resulting from an unqualified airfoil selection and accumulating surface soiling. The high performance low Reynolds profile FX 63-137 is compared to an Eppler-338 wing section as well as to a high performance utility scale wind turbine airfoil, AH 93-W-174 -1ex. We extensively investigated these three different airfoils within the low Reynolds regime between 50,000 and 200,000. This regime is especially important for the starting behavior of a wind turbine, i.e. a quick speed up, and is crucial for small wind turbines because they have more frequent start/stop events. A Reynolds number of 200 k is additionally the operational regime of some sHAWT under the 5-10 kW level. The present study discusses not only the low Reynolds performance of the smooth profiles but investigates the influence of surface soiling. This ranges from 2D disturbances, such as a 0.2mm thin tripwire or several zigzag tapes, up to the simulation of massive sand build up by covering the entire leading edge region with a 40 grit sand paper. The experiments reveal that even small surface soiling has an impact and massive roughness leads in some cases to the loss of 50\% in lift coefficient. The experimental data is used to simulate a sHAWT in different stages of debris. While the peak power was reduced by two thirds compared to the clean configuration the annual energy production has halved under certain conditions.},
   url = {http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2555661},
   publisher = {ASME},
   series = {Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy},
   booktitle = {ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition},
   event_name = {ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition},
   DOI = {10.1115/GT2016-56377},
   author = {Holst, D. and Pechlivanoglou, G. and Kohlrausch, C. T. and Nayeri, C. N. and Paschereit, C. O.}
}

@Article { Hoffmann2015,
   title = {Drag Reduction using Base Flaps Combined with Vortex Generators and Fluidic Oscillators on a Bluff Body},
   journal = {SAE Int. J. Passeng. Cars - Mech. Syst.},
   year = {2015},
   volume = {8},
   number = {2},
   number2 = {2015-01-2890},
   pages = {705-712},
   abstract = {The potential of drag reduction on a generic model of a heavy vehicle using base flaps operated in combination with flow control devices is investigated experimentally. Base flaps are well known as drag reduction devices for bluff bodies and heavy road vehicles. However, for optimal performance their deflection angle should typically not exceed 12\(^{\circ}\). In this paper the primary goal is to increase the usable range of the deflection angles by applying flow control. The secondary goal is to find the most suitable method for flow control. A comparison is made between triangular vortex generators and fluidic oscillators as passive and active flow control methods, respectively. Vortex generators have the advantage of being very simple devices but produce drag. Fluidic oscillators are also quite simple devices but require additional air supply. Their advantages are that they can be activated when needed and that they do not generate additional drag. The wind tunnel model used corresponds to the geometrical dimensions of a 10\% scaled model yielding a Reynolds number of 7·105. Various flap angles with a length of 100mm were attached to the base. Other geometrical parameters such as the height of the vortex generators were also varied as well as their axial position. The results show that base flaps deflected by 20\(^{\circ}\) combined with vortex generators reduce drag by 26\% compared to the baseline. At deflection angles of 22.5\(^{\circ}\) the passive and active concepts show similar drag reduction. Furthermore, possibilities for performance improvement of the active concept are identified.},
   DOI = {10.4271/2015-01-2890},
   author = {Hoffmann, F. and Schmidt, H. J. and Nayeri, C. N. and Paschereit, C. O.}
}

@Article { Oberleithner2015,
   title = {Formation and flame-induced suppression of the precessing vortex core in a swirl combustor: Experiments and linear stability analysis},
   journal = {Combustion and Flame},
   year = {2015},
   volume = {162},
   number = {8},
   pages = {3100-3114},
   keywords = {Precessing vortex core},
   url = {http://www.sciencedirect.com/science/article/pii/S0010218015000577},
   ISSN = {0010-2180},
   DOI = {10.1016/j.combustflame.2015.02.015},
   author = {Oberleithner, K. and St{\"o}hr, M. and Ho Im, S. and Arndt, C. M. and Steinberg, A. M.}
}

@Article { Holst2015,
   title = {Wake Analysis of a Finite Width Gurney Flap},
   journal = {Journal of Engineering for Gas Turbines and Power},
   year = {2015},
   volume = {138},
   number = {6},
   pages = {062602--062602},
   url = {http://dx.doi.org/10.1115/1.4031709},
   publisher = {ASME},
   ISSN = {0742-4795},
   DOI = {10.1115/1.4031709},
   author = {Holst, D. and Bach, A. and Nayeri, C. N. and Paschereit, C. O. and Pechlivanoglou, G.}
}

@Inproceedings { Schwadtke2015,
   title = {BeRT im gro{\ss}en Windkanal},
   year = {2015},
   pages = {218-221},
   publisher = {VDE Verlag},
   booktitle = {Virtuelle Instrumente in der Praxis 2015: Begleitband zum 20. VIP-Kongress},
   ISBN = {978-3800736690},
   author = {Schwadtke, U. and Holst, D. and Paschereit, C. O.}
}

@Inproceedings { Huang2015a,
   title = {Numerical and Experimental Investigation of Wind Turbine Wakes},
   year = {2015},
   number = {AIAA paper no. 2015-2310},
   booktitle = {AIAA Aviation, 45th AIAA Fluid Dynamics Conference, June 22-25, 2015, Dallas, Texas, USA},
   ISBN = {978-1-62410-362-9},
   DOI = {10.2514/6.2015-2310},
   author = {Huang, X. and Vey, S. and Meinke, M. and Schroeder, W. and Pechlivanoglou, G. and Nayeri, C. N. and Paschereit, C. O.}
}

@Inproceedings { Holst2015a,
   title = {Wake Analysis of a Finite Width Gurney Flap},
   year = {2015},
   number = {ASME Paper GT2015-43220},
   pages = {V009T46A017 (13 pages)},
   abstract = {The results of stereo Particle-Image-Velocimetry measurements are presented in this paper to gain further insight into the wake of a finite width Gurney flap. It is attached to an FX 63-137 airfoil which is known for a very good performance at low Reynolds numbers and is therefore used for small wind turbines and is most appropriate for tests in the low speed wind tunnel presented in this study. The Gurney flaps are a promising concept for load control on wind turbines but can have adverse side effects, e.g. shedding of additional vortices. The investigation focuses on frequencies and velocity distributions in the wake as well as on the structure of the induced tip vortices. Phase averaged velocity fields are derived of a Proper-Orthogonal-Decomposition based on the stereo PIV measurements. Additional hot-wire measurements were conducted to analyze the fluctuations downstream of the finite width Gurney flaps. Experiments indicate a general tip vortex structure that is independent from flap length but altered by the periodic shedding downstream of the flap. The influence of Gurney flaps on a small wind turbine is investigated by simulating a small 40 kW turbine in Q-Blade. They can serve as power control without the need of an active pitch system and the starting performance is additionally improved. The application of Gurney flaps imply tonal frequencies in the wake of the blade. Simulation results are used to estimate the resulting frequencies. However, the solution of Gurney flaps is a good candidate for large scale wind turbine implementation as well. A FAST simulation of the NREL 5MW turbine is used to generate realistic time series of the lift. The estimations of control capabilities predict a reduction in the standard deviation of the lift of up to 65\%. Therefore finite width Gurney flaps are promising to extend the lifetime of future wind turbines.},
   booktitle = {Proceedings of ASME Turbo Expo 2015, June 15-19, 2015, Montreal, Quebec, Canada},
   ISBN = {978-0-7918-5680-2},
   DOI = {10.1115/GT2015-43220},
   author = {Holst, D. and Bach, A. and Nayeri, C. N. and Paschereit, C. O. and Pechlivanoglou, G.}
}

@Article { Mitchell2014,
   title = {Coherent structure and sound production in the helical mode of a screeching axisymmetric jet},
   journal = {Journal of Fluid Mechanics},
   year = {2014},
   month = {6},
   volume = {748},
   pages = {822--847},
   url = {http://journals.cambridge.org/article_S0022112014001736},
   ISSN = {1469-7645},
   DOI = {10.1017/jfm.2014.173},
   author = {Edgington-Mitchell, D. and Oberleithner, K. and Honnery, D. R. and Soria, J.}
}

@Inproceedings { Geiser2014a,
   title = {Thermoacoustics of a turbulent premixed flame},
   year = {2014},
   number = {AIAA paper no. 2015-2476},
   booktitle = {AIAA Aviation, 13th AIAA/CEAS Aeroacoustics Conference, 16-20 June 2014, Atlanta, Georgia, USA},
   ISBN = {978-1-62410-285-1},
   DOI = {10.2514/6.2014-2476},
   author = {Geiser, G. and Nawroth, H. and Hosseinzadeh, A. and Zhang, F. and Bockhorn, H. and Habisreuther, P. and Janicka, J. and Paschereit, C. O. and Schroeder, W.}
}

@Article { Krebs2013,
   title = {Comparison of Nonlinear to Linear Thermoacoustic Stability Analysis of a Gas Turbine Combustion System},
   journal = {Journal of Engineering for Gas Turbines and Power},
   year = {2013},
   month = {6},
   day = {24},
   volume = {135},
   number = {8},
   pages = {081503 (8 Pages)},
   ISSN = {0742-4795 (online), 1528-8919 (print)},
   DOI = {10.1115/1.4023887},
   author = {Krebs, W. and Krediet, H. and Hermeth, S. and Poinsot, T. E. P. and Schimek, S. and Paschereit, C. O.}
}

@Article { zhang2013,
   title = {On prediction of combustion generated noise with the turbulent heat release rate},
   journal = {Acta Acustica united with Acustica},
   year = {2013},
   volume = {99},
   number = {6},
   pages = {940-951},
   DOI = {10.3813/AAA.918673},
   author = {Zhang, F. and Habisreuther, P. and Bockhorn, H. and Nawroth, H. and Paschereit, C. O.}
}

@Conference { nawroth2013e,
   title = {Large Eddy Simulation of Premixed Flames Using F-Tacles and ATF Approaches},
   year = {2013},
   booktitle = {Euromech Colloquium 546: Combustion Dynamics and Combustion Noise, May 13-16, 2013, Menaggio, Italy},
   author = {Hosseinzadeh, A. and Nawroth, H. and Janicka, J. and Paschereit, C. O.}
}

@Conference { nawroth2013f,
   title = {Numerical and Experimental Investigation of the Noise Emitted by a Premixed Flame at Various Operating Conditions},
   year = {2013},
   booktitle = {Euromech Colloquium 546: Combustion Dynamics and Combustion Noise, May 13-16, 2013, Menaggio, Italy},
   author = {Geiser, G. and Hosseinzadeh, A. and Nawroth, H. and Zhang, F. and Schr{\"o}der, J. and Janicka, J. and Paschereit, C. O. and Habisreuther, P. and Bockhorn, H.}
}

@Inproceedings { nawroth2013c,
   title = {Flow Investigation and Acoustic Measurements of an Unconfined Turbulent Premixed Jet Flame},
   year = {2013},
   number = {AIAA paper 2013-2459},
   publisher = {American Institute of Aeronautics and Astronautics},
   booktitle = {43rd AIAA Fluid Dynamics Conference, June 24-27, 2013, San Diego, California, USA},
   ISBN = {978-1-62410-214-1},
   DOI = {10.2514/6.2013-2459},
   author = {Nawroth, H. and Paschereit, C. O. and Zhang, F. and Habisreuther, P. and Bockhorn, H.}
}

@Inproceedings { Holst2013,
   title = {Influence of a Finite Width Micro-Tab on the Spanwise Lift Distribution},
   year = {2013},
   number = {ASME paper GT2013-94381},
   pages = {V008T44A011 (10 pages)},
   booktitle = {Proc. ASME Turbo Expo 2013, June 3-7, San Antonio, Texas, USA},
   ISBN = {978-0-7918-5529-4},
   DOI = {10.1115/GT2013-94381},
   author = {Holst, D. and Bach, A. and Nayeri, C. N. and Paschereit, C. O.}
}

@Inproceedings { Hodzic2013,
   title = {Large Eddy Simulation of lean blow off},
   year = {2013},
   number = {AIAA paper 2013-3080},
   pages = {1--13},
   url = {http://arc.aiaa.org/doi/abs/10.2514/6.2013-3080},
   publisher = {American Institute of Aeronautics and Astronautics},
   booktitle = {21th AIAA Computational Fluid Dynamics Conference, June 24-27, 2013, San Diego, California, USA},
   DOI = {10.2514/6.2013-3080},
   author = {Hodizc, E. and Duwig, C. and Szasz, R. and Kr{\"u}ger, O. and Fuchs, L.}
}

@Inproceedings { Bach2013,
   title = {Transitional Effects of Active Micro-Tabs for Wind Turbine Load Control},
   year = {2013},
   number = {ASME paper GT2013-94369},
   pages = {V008T44A010 (8 pages)},
   booktitle = {Proc. ASME Turbo Expo 2013, June 3-7, San Antonio, Texas, USA},
   ISBN = {978-0-7918-5529-4},
   DOI = {10.1115/GT2013-94369},
   author = {Bach, A. and Holst, D. and Nayeri, C. N. and Paschereit, C. O.}
}

@Inproceedings { Krebs2012,
   title = {Comparison of nonlinear to linear thermoacoustic stability analysis of a gas turbine combustion system},
   year = {2012},
   number = {ASME paper GT2012-69477},
   pages = {1113-1124 (12 pages)},
   booktitle = {Proc. ASME Turbo Expo 2012, June 11-15, Bella Center, Copenhagen, Denmark},
   ISBN = {978-0-7918-4468-7},
   DOI = {10.1115/GT2012-69477},
   author = {Krebs, W. and Krediet, H. and Hermeth, S. and Poinsot, T. E. P. and Schimek, S. and Paschereit, C. O.}
}

@Inproceedings { nawroth2012a,
   title = {Experimental and Numerical Investigation of a Turbulent Premixed Flame in an Anechoic Environment},
   year = {2012},
   number = {AIAA paper 2012-3072},
   url = {http://arc.aiaa.org/doi/abs/10.2514/6.2012-3072},
   publisher = {American Institute of Aeronautics and Astronautics},
   booktitle = {42nd AIAA Fluid Dynamics Conference, June 25-28, 2012, New Orleans, Louisiana, USA},
   DOI = {10.2514/6.2012-3072},
   author = {Nawroth, H. and Saurabh, A. and Paschereit, C. O. and Zhang, F. and Habisreuther, P. and Bockhorn, H.}
}

@Article { Petz2011,
   title = {Global modes in a swirling jet undergoing vortex breakdown},
   journal = {Physics of Fluids},
   year = {2011},
   volume = {23},
   number = {9},
   pages = {091102},
   keywords = {bifurcation; confined flow; flow visualisation; fluid oscillations; jets; nozzles; shear turbulence; vortices;},
   publisher = {AIP},
   ISSN = {1070-6631 (print), 1089-7666 (online)},
   DOI = {10.1063/1.3640007},
   author = {Petz, C. and Hege, H. C. and Oberleithner, K. and Sieber, M. and Nayeri, C. N. and Paschereit, C. O. and Wygnanski, I. and Noack, B. R.}
}

@Article { Oberleithner2011a,
   title = {Three-dimensional coherent structures in a swirling jet undergoing vortex breakdown: stability analysis and empirical mode construction.},
   journal = {Journal of Fluid Mechanics},
   year = {2011},
   volume = {679},
   pages = {383-414},
   abstract = {The spatio-temporal evolution of a turbulent swirling jet undergoing vortex breakdown has been investigated. Experiments suggest the existence of a self-excited global mode having a single dominant frequency. This oscillatory mode is shown to be absolutely unstable and leads to a rotating counter-winding helical structure that is located at the periphery of the recirculation zone. The resulting time-periodic 3D velocity field is predicted theoretically as being the most unstable mode determined by parabolized stability analysis employing the mean flow data from experiments. The 3D oscillatory flow is constructed from uncorrelated 2D snapshots of particle image velocimetry data, using proper orthogonal decomposition, a phase-averaging technique and an azimuthal symmetry associated with helical structures. Stability-derived modes and empirically derived modes correspond remarkably well, yielding prototypical coherent structures that dominate the investigated flow region. The proposed method of constructing 3D time-periodic velocity fields from uncorrelated 2D data is applicable to a large class of turbulent shear flows.},
   note = {Available on CJO},
   url = {http://journals.cambridge.org/article_S0022112011001418},
   DOI = {10.1017/jfm.2011.141},
   author = {Oberleithner, K. and Sieber, M. and Nayeri, C. N. and Paschereit, C. O. and Petz, C. and Hege, H. C. and Noack, B. R. and Wygnanski, I.}
}

@Inproceedings { Lacarelle2010a,
   title = {Modeling the fuel/air mixing to control the pressure pulsations and NOx emissions in a lean premixed combustor},
   year = {2010},
   month = {4},
   volume = {108},
   pages = {307--321},
   abstract = {This paper presents an overviewof the methodology developed to predict, control and optimize the NOx emissions and stability of lean premixed combustors. Investigations are performed firstly in cold flow and are validated with reacting flow measurements. A new cold flow mixing model describes the relevant characteristics of the fuel/airmixing, i.e. themixing quality and convective time delays, for different operating points of the system.Measurements in the combustor are performed to correct the flame position effect or calibrate the cold flowresults.The model is for the first time implemented in an extremum seeking controller to optimize the emissions and pressure pulsations of the combustor by adjusting the fuel mixing profile. A further increase of the fuel/air mixing, necessary for further NOx reductions, with pulsating fuel injection, is demonstrated. At the end, the developed adaptive control strategies demonstrate opportunities for future efficiency increases in industrial combustors.},
   editor = {King, Rudibert},
   publisher = {Springer-Verlag Berlin},
   series = {Notes on Numerical Fluid Mechanics and Multidisciplinary Design},
   booktitle = {Active Flow Control II, Papers Contributed to the Conference ''Active Flow Control II 2010'', Berlin, Germany, May 26 to 28, 2010},
   ISBN = {978-3-642-11734-3 (print), 978-3-642-11735-0 (online)},
   DOI = {10.1007/978-3-642-11735-0_20},
   author = {Lacarelle, A. and Moeck, J. P. and Paschereit, C. O. and Gelbert, G. and King, R. and Luchtenburg, D. M. and Noack, B. R. and Kasten, J. and Hege, H. C.}
}

@Inproceedings { Uruba2010,
   title = {Spatio-Temporal Analysis of Swirling Jets Undergoing Vortex Breakdown},
   year = {2010},
   url = {http://www.it.cas.cz/files/u1868/Uruba-Ober-Sieber-Hladik-SB.pdf},
   address = {Prague},
   booktitle = {Colloquium Fluid Dynamics, Institute of Thermomechanics AS CR, v.v.i., Prague, 20--22 Oct},
   author = {Uruba, V. and Oberleithner, K. and Sieber, M. and Hladik, O.}
}

@Inproceedings { Nayeri2009,
   title = {Drag Reduction on a Generic Tractor-Trailor Using Active Flow Control in Combination with solid flaps},
   year = {2009},
   pages = {179-191},
   editor = {Browand, McCallen, Ross},
   booktitle = {Lecture Notes in Applied and Computational Mechanics 41 ''The Aerodynamics of Heavy Vehicles II: Trucks, Buses and Trains''},
   ISBN = {1613-7763},
   author = {Nayeri, C. N. and Greenblatt, D. and Haff, J. and Paschereit, C. O. and L{\"o}fdahl, L.}
}

@Inproceedings { Harr2009,
   title = {Feasibility study of a recuperated turboshaft-engine based on a micro-gasturbine},
   year = {2009},
   number = {ASME paper GT2009-59204},
   pages = {55-62},
   abstract = {The present paper shows the current state of a feasibility study of the University of Applied Sciences Esslingen. The intention of this study is the conversion of a model-turbine into a turboshaft-engine for variable applications, with as few as possible modifications. The shaft power of the engine is estimated on 20 kW at least. It is intended to use a recuperator to augment its efficiency. After a general introduction possible applications are discussed and the previous design-process is explained: Subsequent to the concept-phase cycle parameters were calculated and the power turbine was designed and manufactured. At present turbine tests are running. The recuperator is of counter flow type. To shorten the flow path it is mounted directly around the combustor. Currently different variations are being designed which will be optimised. The pressure loss within the exhaust manifold between power turbine and recuperator has already been reduced by simulations and tests. This will be minimised through application of a genetic optimisation software.},
   url = {http://link.aip.org/link/abstract/ASMECP/v2009/i48869/p55/s1},
   publisher = {ASME},
   booktitle = {Proc. ASME Turbo Expo 2009: Power for Land, Sea, and Air (GT2009), June 8-12, Orlando, Florida, USA},
   ISBN = {9780791838495 (DVD), 978-0-7918-4886-9 (online)},
   DOI = {10.1115/GT2009-59204},
   author = {Harr, C. and Paschereit, C. O. and G{\"a}rtner, U.}
}

@Inproceedings { Hoefener2009,
   title = {Wind tunnel experiments of a high speed train exposed to cross wind on ground and bridge configurations},
   year = {2009},
   booktitle = {EUROMECH COLLOQUIUM 509 ''Vehicle Aerodynamics External Aerodynamics of Railway Vehicles, Trucks, Buses and Cars'', 24-26 M{\"a}rz 2009, Berlin, Germany},
   author = {Hoefener, L. and Romann, D. and Nayeri, C. N. and Tielkes, Th. and Paschereit, C. O.}
}

@Inproceedings { Paschereit2000c,
   title = {Identification and control of unstable modes in an isothermal and reacting swirling jet},
   year = {2000},
   volume = {VIII},
   pages = {101-104},
   editor = {Dopazo, C.},
   series = {Proceedings of the 8th European Turbulence Conference, Barcelona, Spain 27-30 June 2000},
   booktitle = {Advances in Turbulence},
   author = {Paschereit, C. O. and Gutmark, E. J. and Haber, L.}
}

@Inproceedings { Paschereit2000d,
   title = {Numerical and experimental analysis of acoustically excited combustion instabilities in gas turbines},
   year = {2000},
   booktitle = {6th AIAA/CEAS Aeroacoustics Conference, June 12-14, 2000, Maui, Hawaii},
   author = {Paschereit, C. O. and Flohr, P. and Gutmark, E. J. and Haber, L.}
}