Wind Energy research

Institute of Aerodynamics und Gas Dynamics

Current and completed projects


Current projects of our working group are:

In order to be able to generate electricity with the help of wind turbines, the incoming air mass is decelerated via the rotor disk. Therefore, there is a wake behind the wind turbine, which can be divided into two regions and has a wind speed deficit compared undisturbed air flow. In the "near-wake" area of the wind turbine wake there are, among other things, the helical structures of the rotor blade tip vortices. These shield this area from the ambient flow and thus prevent a rapid freshening of the wind field. However, these helical structures are not stable and decay after a certain distance behind the wind turbine. This marks the beginning of the "far-wake". This decay of the helical structures leads to turbulent mixing of the wake, which in turn leads to a compensation of the velocity deficit. Especially with respect to wind farms, where many wind turbines are located one behind the other, this process of breakdown of the helical structures of the wake is of great interest, since wind turbines that are in the wake of a preceding turbine have significant performance losses due to the lower inflow velocities.

For this reason, the helical structures in the wake are investigated in cooperation with the TU Berlin within the DFG-funded project "UBeRT". The focus is on the dynamics of the helical structures as well as on the destabilization of these with different perturbations (long wavelength, short wavelength). In order to gain a fundamental understanding of this, both experiments and numerical simulations are performed for this purpose. The experiments will take place at the Underwater Berlin Research Turbine (UBeRT) in the water towing channel of the TU Berlin. These experiments serve as a comparison to the data from the numerical simulations performed at the IAG. Both in the experiment and in the simulation, disturbance-free as well as disturbance-affected (long-wave, short-wave) wakes of the turbine are investigated. With the help of this close cooperation between the TU Berlin and the IAG, fundamental knowledge in this field will be gained. The numerical simulations also include a turbine of the 15MW class. The results of the simulation can then be compared with the results of the UBeRT in order to investigate scaling effects and the transferability to real wind turbines.

The WINSENTvalid project aims to validate the numerical methods developed in WINSENT using measured data. The validated models will be suitable for both flow modeling and wind turbine design at complex wind energy sites worldwide. At the end of the project, the test site will be able to be used as a real and numerical platform in complex terrain for basic and applied research by academia and industry.

At IAG, the focus is on the high-fidelity CFD tool chain and its validation with sensor data from the WindForS test field. As part of the project, the most accurate 3D geometry of new turbine blades will be analyzed individually and used to provide 3D polars for use in engineering models and code-to-code comparisons, as these, together with meteorological mast data, allow reliable identification of the causes of inaccuracies. A complete turbine will also be simulated and supplemented with forest and terrain models developed at IAG. Data measured on the turbine will be used to validate the aeroelastic model developed in WINSENT, which includes both beam and shell models. Finally, different forest foliage densities, atmospheric stabilities, turbulence intensities and wind speeds and their influence on the interaction between the local wind situation and the turbine will be investigated to gain important insights into turbine loading, efficiency and turbine wake length.

Sabrina Haubold

This research project, funded by the Boysen Foundation, aims to answer the question, to what extend active flow control through micro-suction can reduce flow-induced noise on wind turbines while at the same time improving the aerodynamic efficiency. Numerical methods with different accuracy are applied for this purpose. On the one hand, scale-resolving methods with high temporal and spatial resolution are used. The very high accuracy and detail resolution of these methods captures the flow-physical processes in the interaction of the suction with the flow around the rotor blade segments and thus the effect of the micro-suction on the acoustic sources. On the other hand, more computationally efficient methods are selected for parametric studies on different suction configurations and inflow conditions, providing a basis for evaluating the potential for noise reduction and performance enhancement through micro-suction.

Vortex structures with vorticity in chord direction ω_x of an airfoil with high relative thickness without VGs (top) and with VGs (bottom). The VGs reduce greatly the separation on the airfoil. Computed with Detached Eddy Simulation.
Vortex structures with vorticity in chord direction ω_x of an airfoil with high relative thickness without VGs (top) and with VGs (bottom). The VGs reduce greatly the separation on the airfoil. Computed with Detached Eddy Simulation.

Cost savings on turbines are often coupled with weight savings on the rotor. However, these are only possible through load-adapted design and technological advances. Essential for this is the most accurate possible determination of the site-specific turbine loads, taking into account the changed design requirements for low wind sites. Computational Fluid Dynamics (CFD) methods are suitable for this purpose. Their goal is to precisely capture all parameters that are relevant for the load spectrum. Effects such as atmospheric inflow, orography, the flexible structural response of the components or the control of the turbines play an important role. It can also be used to investigate in detail various approaches for improving the performance of the turbines.

The overall scientific goal in the IndianaWind project is to apply and specifically extend the CFD-based simulation environment for wind turbines developed by the IAG in order to contribute to the most comprehensive and multidisciplinary numerical representation of the wind turbine possible. A new aspect is the extension of the simulation chain for the incorporation of arbitrary specifications from the operational management. Regarding the acoustic radiation, the primary goal is to determine and analyze the influence of the operational management on low-frequency noise components.

In addition, scale-resolving simulation methods are to be tested with regard to their industrial suitability. These are used for investigations of flows with high turbulence. Within the scope of this project, they will primarily be used to investigate thick airfoils with a tendency to flow separation as well as airfoils with blunt trailing edges (flatbacks). The aerodynamic and aeroacoustic behavior of these flatbacks has been little studied to date. While the aerodynamics are important for the loads and the efficiency of the turbine, the emitted sound of these profiles plays an important role in the acoustic evaluation of the turbines and ultimately in the acceptance by the public.

Another application of the hybrid RANS/LES methods in this project is the flow around blade segments equipped with vortex generators (VGs). First, the detailed flow-physical behaviour of the VGs for delaying the flow separation at the blade segment will be evaluated with Detached Eddy Simulations (DES). For the simulative implementation of VGs on the overall rotor, a substitute model is implemented in which only the effect of the VGs on the flow is considered using a suitable source term distribution. This eliminates the need for complex and time-consuming mesh generation of the hundreds of VGs mounted on a rotor blade.

Bild 2: Description: vorticity structures with vertical vorticity for different inflow conditions as well as orographic conditions.



Lighthouse simulation


During operation, a wind turbine is controlled by various very complex control laws, which are intended to optimise performance and protect against extreme events. In particular, the intervention of the controller in the event of an extreme meteorological event, such as a rapid change in wind direction or speed, must be tested simulatively before damage can occur to the wind turbine in the field. The video was created as part of the IndianaWind research project.

The video was created as part of the BMWK-funded IndianaWind research project.

Video transcription

Image source image 2: Wenz, F., Langner, J., Lutz, T., & Krämer, E. (2022). Impact of the wind field at the complex-terrain site Perdigão on the surface pressure fluctuations of a wind turbine. Wind Energy Science, 7(3), 1321–1340.

MERIDIONAL - Multiscale Modelling for Wind Wind Farm Design, Performance Assessment and Loading

the MERIDIONAL project, the IAG acts together with the SWE (Stuttgart Wind Energy) and HLRS (High Performance Computing Center Stuttgart) of the University of Stuttgart inside a large European initiative coordinated by the Delft University of Technology. The purpose of the initiative is to improve the current state-of-the-art understanding of turbulent inflow conditions for wind turbine parks and develop a comprehensive toolchain based on an open-source platform for the evaluation of the interactions between meteorological conditions, wind turbines and wind farms.

For this, the IAG conducts high fidelity Computational Fluid Dynamics CFD studies with its continuously updated code FLOWer and runs high resolution URANS and DDES simulations of wind turbines and wind farms. This includes the two instrumented research turbines that are currently being erected within the WINSENT project and for which detailed measurements of the local wind fields including deformations of the turbines are planned. In particular, interactions of a turbulent atmospheric inflow with wind turbines are investigated. Complex terrain orography, buildings or vegetation as well as fluid-structure interactions are also considered. Similarly, the influence of local atmospheric turbulence on the characteristics of the turbine wake will be studied. Measurement data from different field measurements will be available to validate the simulations.

Finally, the simulations will help validate the results using experimental data and provide data to the project partners to verify lower fidelity methods. The other partners are Danmarks Tekniske Universitet Technische, Universität München, Politecnico di Milano, ICONS, Whiffle, Airborne Wind Europe, Kitepower, Kitekraft, Kitenergy, and the National Renewable Energy Laboratory.

Former Projects

Within the BMWi funded project WINSENT a wind energy test field for the research of wind energy use in complex terrain is established and simulated by numerical models.

The expansion of wind energy as a renewable, climate-friendly source of energy is supported by the BMWi-funded WindForS Project


by the construction of a wind energy test field. Within the project, two research wind turbines will be installed in the mountainous complex terrain of the Swabian Alb. The turbines will have a hub height of approx. 75 metres and a rotor diameter of approx. 50 metres.
The wind fields in the terrain will be characterized by measuring masts equipped with various sensors for speed measurement. In addition, a model chain will be developed within the framework of the project in order to carry out realistic CFD simulations.

The aim of the research project is to gain a better understanding of the flow field and power generation of wind energy in complex terrain in order to profitably exploit the wind's velocity increase over the edge of the terrain.

Involved in the WINSENT project are, besides the University of Stuttgart, the Technical University of Munich, the Esslingen University of Applied Sciences, the Karlsruhe Institute of Technology, the Center for Solar Energy and Hydrogen Research Baden-Württemberg, the Eberhard Karls University of Tübingen and the Aalen University of Applied Sciences.

The project consists of smaller subprojects with different objectives:

Subproject FoWEA

Im Rahmen des Teilprojektes FoWEA werden numerische Modelle der Anlage erstellt und durch Vergleich mit Messdaten validiert. Das IAG entwickelt die Fluid-Struktur-Kopplung zwischen dem CFD Strömungslöser FLOWer und dem FEM-Löser Kratos, der von der TUM erweitert wird. Balken- und Schalenmodelle der Anlagenstruktur werden erstellt und die Ergebnisse der aeroelastischen Berechnungen verglichen. Zur Bewertung der FLOWer- Kratos Kopplung wird ein Vergleich mit Ergebnissen einer Kopplung von FLOWer mit dem Mehrkörpersimulationstool SIMPACK durchgeführt. Zusätzlich werden Feldmessungen und vereinfachte BEM- basierte Modelle mit diesen Ergebnissen verglichen.

Subproject Mikroklima

Im zweiten Teilprojekt Mikroklima werden Einflüsse mikrometeorologischer und topographischer Effekte auf das lokale Strömungsfeld untersucht. Es werden Messungen und Simulationen vor und nach Errichtung der beiden Windenergieanlagen durchgeführt, um Veränderungen des Windes im Testfeld zu bestimmen. Am IAG werden hochaufgelöste instationäre Simulationen mit Hilfe von Einströmdaten der Projektpartner durchgeführt, um so realistische Anströmbedingungen der Windenergieanlagen über die bewaldete Hangkante des Geländes hinweg zu erhalten. Hierzu müssen Implementierungen von thermischer Schichtung, Vegetationsmodellen und Rauigkeitswechseln etc. im Strömungslöser FLOWer eingearbeitet werden.

Musik / Music in Video: 'Voyager' composed and perfomed by Lamass,
licenced through
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Within the cooperative Graduate Program "Windy Cities", the wind energy usage in urban environment will be analysed through numerical simulation models. The cooperative Graduate Program is funded by Ministerium für Wissenschaft, Forschung und Kunst of Baden Württemberg.

"Loads and performance of small wind turbines in urban environment" is one of the projects of Windy Cities Graduate Program. In urban environment, due to complex instationary and strongly varying local inflow, the dynamic loads and performance of small wind turbine is significantly influenced. In this Project, the small wind turbines, which are installed in urban environment, will be simulated with high temporal and spatial resolution CFD.

The acceptance of wind turbines and wind parks is significantly influenced by their acoustic perception in the population. However, the noise mechanisms and various noise types of wind turbines are complex. Therefore, they are only incompletely understood and therefore difficult to predict and hence associated with potential economic risks for the operators. Due to the high density of wind turbines in northern Germany, development in the south is likely to increase in the future. A significant difference between the two regions is the nature of the terrain. In complex hilly terrain such as that found in southern Germany, the forecast uncertainty of noise generation and propagation is further increased. Orography, for example, requires increased consideration of the direction of radiation. In order to be able to use wind energy there economically, ecologically and with broad acceptance by the population, the typical, mostly gusty and turbulent wind regimes and noise propagation must be taken into account.

Within the scope of the research project Schall_KoGe, time-resolved CFD simulations of the flow around a wind turbine are performed at the IAG, taking into account the fluid-structure interaction in complex terrain. The results will be used to investigate the formation of acoustic sound waves in the low-frequency range. In order to extend the frequency range, models for improved prediction of the dominant sound sources of modern wind turbines in the higher frequency range (Inflow Noise and trailing edge noise) are developed on the basis of combined CFD-based simulations. Furthermore, the influence of vortex generators (VG) on aeroacoustics is evaluated with respect to their direct sound emission as well as their influence on the trailing edge emission of the rotor due to the modifications of the boundary layer characteristics.

In the HeliOW project, the wake of offshore wind turbines is being investigated in more detail. Special attention is paid to the effect of the wake on the flight of helicopters through these wake. It will be investigated which and how serious possible influences on the flight of helicopters are. The background of the research results from the necessity of maintenance of offshore wind turbines and the associated use of maintenance helicopters. In the project, two approaches are pursued to address these issues. On the one hand, high-resolution CFD simulations of the wake will be performed, which will then be fed into a helicopter simulator of the project partners in Braunschweig and Munich. Secondly, the helicopter wake in the wake of the wind turbine is directly considered in the flow simulation. Finally, it should be possible to make statements about the influence on the flight physics of the helicopters.


© IAG Uni Stuttgart

In this video, the decommissioned rotor is turned out of the wind in the so-called "L-position" for maintenance work, whereby large flow separations take place behind the cross-flow, angular nacelle. The nominal wind speed and the maximum wind speed designed for the turbine are simulated to investigate a normal and an extreme case. These cases were simulated with the DES method and the Lambda-2 isosurfaces of the vortex structures are shown here. Pilot studies with these flow fields will be carried out at the project partners with a helicopter flight simulator to determine the effects on helicopter flight dynamics".

Video transcription

Im Hinblick auf die Erhöhung der Akzeptanz der Windenergie und zur Erfüllung verschärfter Anforderungen an den Lärmschutz gewinnt die Reduktion der Emissionen von Windenergieanlagen beim Entwurf neuer Anlagen eine wichtige Bedeutung. Diese Emissionen können sich sowohl über die Luft in Form von Schall, als auch durch den Boden in Form von Erschütterungen (Körperschall) ausbreiten.
Während hochfrequente Emissionen (hauptsächlich Luftschall) gut erforscht sind und objektive Bewertungskriterien vorliegen, sind die Mechanismen die zu niederfrequenten Emissionen führen weitgehend unbekannt.
Im Rahmen des Forschungsprojekts TREMAC sollen Prognose- und Simulationsmodelle für niederfrequente Emissionen von Windkraftanlagen entwickelt werden. Auf Grundlage der Erkenntnisse sollen Optimierungsstrategien zur Minderung der Schall- und Erschütterungsemissionen durch konstruktiven Maßnahmen erstellt werden. Parallel dazu finden fundierte umweltmedizinische sowie umweltpsychologische Studien zur Wirkung von der Emissionen auf Anwohner statt. Insgesamt zielt das Vorhaben auf eine objektive Bewertung der Schall- und Erschütterungsbelastung von WEA ab.

Arbeiten am IAG:

Unter Anwendung hochaufgelöster Fluid-Struktur-gekoppelter CFD Simulationen wird am IAG ein Simulationsmodell aufgebaut, das aerodynamische und strukturmechanische Effekte und deren Wechselwirkung auf die Emissionen der WEA berücksichtigt. In Simulationsstudien wird der Einfluss von Parametern wie die Art der Anströmung oder die Anzahl der Freiheitsgrade im Strukturmodell auf die Emissionen untersucht. Es sollen dabei vor allem Erkenntnisse über die aerodynamisch induzierten Emissionen gewonnen werden. In einer gemeinsamen Prozesskette werden am IAG mit dem entwickelten Simulationsmodell zeitsynchrone akustische und mechanische Emissionen berechnet. Diese dienen als Randbedingungen für Ausbreitungsrechnungen am Institut für Bodenmechanik und Felsmechanik des KIT. Mit dieser Prozesskette, sollen die Emissionen von der Entstehung bis zum Beobachter nachgebildet werden. Anhand von Freifeldmessungen soll eine Plausibilisierung der Simulationsergebnisse stattfinden und die Möglichkeiten und Einschränkungen der numerischen Prozesskette bewertet werden.



Hintergrund und Problemstellung

Die Motivation für das EU-Forschungsprojekt AVATAR liegt in den Entwicklungsherausforderungen, die sich aus immer größer werdenden Windenergieanlagen ergeben. Um Anlagen mit einer Leistung von 10-20 MW möglich zu machen, müssen neue Designmethoden untersucht und angewandt werden. Dies sind beispielsweise lange, schlanke Blätter mit definierten aeroelastischen Eigenschaften, große Profildicken, hohe Schnellaufzahlen und die geziehlte Verwendung von Flow Control Devices. Sie ermöglichen noch größere Rotordurchmesser und somit eine Steigerung der Energieertrags. Allerdings erfordern diese Innovationen eine Überarbeitung der aktuell angewandten Entwicklungswerkzeuge (z.B. der Blattelement-Methode), da sie aus aerodynamischer und aerelastischer Sicht außerhalb des validierten Bereichs liegen. Durch höhere Gechwindigkeiten treten Kompressibilitäts- und Turbulenzeffekte auf, die bisher vernachlässigt werden konnten. Zusätzlich sind die Annahmen bezüglich Transitions- und Ablöseverhalten nicht mehr gültig und das Verhalten des Rotorblattes wird stark durch aeroelastische Interaktionen bestimmt. Das Ziel des AVATAR-Projekts ist daher die Evaluation, Verbesserung und Validierung der bisher verwendeten Entwicklungsmethoden hinsichtlich dieser neuen Effekte und Herausforderungen. Das Projekt wird im Rahmen der EERA (European Energy Research Alliance) durchgeführt und besteht aus zahlreichen europäischen Projektpartnern. EERA Homepage | AVATAR Homepage

Arbeiten am IAG

Am IAG sollen auf Basis der CFD-CSD Berechnungskette hochgenaue Simulationen durchgeführt werden um die auftretenden Effekte zu identifizieren und charakterisieren. Der Fokus liegt hierbei auf der Interaktion der Anlage mit atmosphärischer Turbulenz. Zusätzlich sollen die Möglichkeiten zur Lastreduktion durch Hinterkantenklappen untersucht werden, im speziellen mit Hinblick auf großer, elastische Rotoren.

Ansprechpartner: Dipl.-Ing. Annette Fischer, Dr.-Ing. Thorsten Lutz

Hintergrund und Problemstellung

Um die Energieausbeute zu erhöhen wurden in den vergangenen Jahren Windenergieanlagen mit zunehmend größerem Rotordurchmesser entwickelt. Eine weitere signifikante Vergrößerung der Rotoren erfordert die Entwicklung neuer Konzepte und Technologien, um einen überproportionalen Anstieg von Gewicht und Herstellungskosten zu vermeiden und die Energie-Erzeugungskosten zu senken. Das gemeinsame Ziel des Forschungsschwerpunktes besteht in der Entwicklung und Bewertung innovativer Konzepte zur Lastenkontrolle. An dem Projekt sind neben der Universität Stuttgart die TU Berlin, die RWTH Aachen, die TU Darmstadt und die Carl von Ossietzky Universität Oldenburg beteiligt.

Arbeiten am IAG

Am IAG soll eine hochgenaue CFD-basierte Berechnungskette weiterentwickelt und zur Berechnung der instationären Lasten einer Windenergieanlage mit bzw. ohne aktivierter Lastenkontrolle angewendet werden. Dabei soll eine realitätsnahe atmosphärische Zuströmung mit zeitlich aufgelöster Turbulenz betrachtet werden. Die Komplexität der betrachteten Konfiguration sowie der Zuströmung wird dabei sukzessive erhöht, um spezifische Einflüsse gezielt untersuchen zu können, Vergleiche mit Windkanalversuchen der Universität Oldenburg und der TU Darmstadt zu ermöglichen und schließlich Daten zur Verbesserung vereinfachter Berechnungsverfahren der TU Berlin und der TU Darmstadt zu liefern. Da sich die Windkanalversuche nur im Modellmaßstab durchführen lassen wird das entwickelte numerische Verfahren zur Bewertung der Wirksamkeit des Lastenkontrollkonzepts für eine generische Anlage im Original-Maßstab unter atmosphärischen Bedingungen genutzt.

Im Rahmen des durch das europäische Vorhaben IRPWind finanzierte Forschungsprojekt UNAFLOW soll die instationäre Aerodynamik einer schwimmenden Windenergieanlage untersucht werden. Ein dynamisch skaliertes Modell der Referenzturbine “DTU 10MW” soll unter Rotations- und Translationsschwingungen der gesamten Anlage analysiert werden. Dadurch sollen im hochfrequenten Bereich typische wind- und wellenbedingt angeregte Bewegungen einer Offshore-Plattform nachgebildet werden.
Somit soll ein tieferer Einblick in die damit verbundenen komplexen, instationären Effekte auf den Rotor und den Nachlauf gewonnen werden. Dabei werden sowohl Messungen in dem Grenzschichtwindkanal von PoliMi als auch numerische Strömungssimulationen durchgeführt. Am IAG sollen hochaufgelöste CFD Simulationen der Anlage bei ausgewählten Betriebszuständen mit dem Strömungslöser FLOWer durchgeführt werden, um detaillierte Strömungsdaten unter diesen instationären Bedingungen zu generieren. Die numerischen Ergebnisse sollen mit den von Projektpartnern bereitgestellten Windkanaldaten verglichen und für die Validierung der numerischen Methoden herangezogen werden.

Background of the AssiSt project

Contact: Pascal Weihing

As part of the joint project AssiSt (Plant Flow Simulation and Site Calibration), a contribution was made to further develop simulation approaches from university and large-scale research and apply them to new innovative product series and operating modes of wind turbines. The central goal was the transient simulation of complete wind turbines with high-resolution numerical methods in the field for aerodynamic load and power prediction in order to be able to transfer these into the industrial design process. Realistic boundary condition specifications for the inflow and throughflow of the integration domain, i.e. the plant near field, were developed and entered into the industrially used CFD solver. The physics of the nacelle bypass flow was studied in detail and optimised for its performance-enhancing flow displacement with rotating spinner, fixed nacelle part and the air flows from the generator cooling.


Work at IAG

Two main objectives were pursued at the IAG. On the one hand, a coupling of the wind fields from the meteorology code PALM of the project partner IMUK with the code FLOWer used at the IAG for the detailed flow simulation of the wind turbines was carried out. The methodical process chain for the simulation of wind turbines in complex terrain with atmospheric inflow was extended. The effects of the turbulent inflow in the complex terrain were evaluated in relation to the rotor loads. Another important work package dealt with the detailed flow around the rotor blade/nacelle transition. The influence of a voluminous nacelle on the aerodynamics of the rotor in the interior area was analysed and new insights into the complex frictional flow on the nacelle and on the blade interior area could be gained. The influence of the nacelle geometry was systematically investigated in order to optimize the performance of the overall rotor. In the process, measures could be developed which led to a reduction of the performance-reducing flow separation in the inner area of the rotor.

ActiQuiet / ActiQuieter

Benjamin Arnold


The expansion of wind energy is an important pillar with regard to the energy turnaround decided by politics. However, expansion on land in particular is accompanied by ever larger plant dimensions and shorter distances to inhabited areas. At the same time, the noise pollution of local residents is increasing. On the basis of field measurements, flow-induced rear edge noise could be detected as the dominant noise source of wind turbines. Methods to reduce trailing edge noise are passive and active in nature. Passive methods include, for example, the design of special profile geometries or modifications of the trailing edge shape. Active methods require the supply of external energy, but can also be optimally adapted to the respective inflow condition. At the Institute for Aerodynamics and Gas Dynamics (IAG) at the University of Stuttgart, the potential of surface boundary layer suction to reduce rear edge noise was investigated. In a first step, the trailing edge noise emissions of a typical wind energy profile could be reduced both experimentally and numerically in the ActiQuiet project. This potential was successfully demonstrated in the follow-up project ActiQuieter by CFD-based design calculations for a generic wind turbine as well as an industrial plant. By the consideration of a modern, industrial wind energy plant the feasibility of surface boundary layer extraction for noise reduction should be mathematically examined under consideration of all relevant, industrial boundary conditions. The results are promising: Noise reductions are accompanied by a net improvement of the drive power over a wide range, i.e. the improvement of the aerodynamics through active flow control dominates the required pump performance. With regard to the improvement of the drive power, a maximum is formed from which a further reduction of the trailing edge noise leads to losses in aerodynamics. Only very high noise reduction levels result in a net deterioration of the system performance. The bottleneck of this promising potential is the pump, which has to meet very high requirements. An increase in the number of pumps combined with a reduction in the individual pump capacity required can serve as a remedy.

Im Projekt VortexLoads sollen die im EU-Projekt AVATAR beobachteten Unterschiede in den mit Vortex-Wake-Models berechneten Ermüdungslasten im Vergleich zu Ergebnissen der Blade-Element-Momentum-Modelle (BEM) validiert werden. Dazu liefert das IAG CFD-Ergebnisse eines 10MW Rotors unter turbulenter Anströmung als numerische Vergleichsdaten für die mit den Modellen berechneten transienten Lasten.
Ein Teilaspekt dieses Projekts ist dabei konsistente Strömungsbedingungen am Rotor in den verschiedenen Berechnungsmethoden zu gewährleisten, um einen Vergleich der Ergebnisse zu ermöglichen. Während in der CFD die Turbulenz-Propagation sowie -Entwicklung bis zur Rotorebene berechnet wird, nutzen die BEM-Modelle direkt den Strömungs-Input in der Rotorebene. Daher werden Untersuchungen durchgeführt, um den Einfluss des Rotors in der CFD auf das Strömungsfeld stromauf zu quantifizieren. Dies ermöglicht dann ein vom Rotor unbeeinflusstes Strömungsfeld aus der CFD-Simulation zu extrahieren und mittels eines Zeitversatzes als zeitsynchronen Input in den BEM-Modellen zu nutzen.


In the joint research project "Evaluation of relevant noise sources from wind turbines under real atmospheric inflow conditions (INFLOW-Noise)", the relevance of the noise caused by turbulent inflow at leading edges of rotor blade profiles of wind turbines was investigated. The models used so far in industry to determine such noise sources were derived mainly from theoretical considerations and wind tunnel tests without realistic turbulence similar to wind. Within the project, numerical flow simulations were used to generate wind-like fields, which were fed into aerodynamic and aeroacoustic simulations carried out by IAG on an aerodynamic blade profile of a wind turbine.
The results were compared with a noise prediction program used in industry. To validate the methods, acoustic tests with turbulent inflow were carried out on an aerodynamic profile in the wind tunnel of the University of Oldenburg. A fractal grid was used to generate realistic turbulence.

The results from the simulations of the complex wind tunnel construction carried out by IAG could be validated very well with the measurements from the wind tunnel. The comparison of the aeroacoustic simulation with the industrial code showed that the noise emissions caused by inflow noise are already quite well calculated by the industrial code. However, the comparison of the directivity between aeroacoustic simulations and the industrial code showed different results. The results obtained can be used to improve industrial computational models. The influence of the profile geometry on the emissions of the inflow noise is limited in the relevant frequency range. A stronger change of the profile geometry may generate advantages for the inflow noise, but would be at the expense of the aerodynamic performance.

A WindForS project sponsored by the BMWi

is the project KonTest



Contact: Mohammad Kamruzzaman, Dr.-Ing. Thorsten Lutz, Dr.-Ing. Werner Wuerz

In the European joint research project UpWind, a CFD-based method for predicting the trailing edge noise of profiles was developed at the IAG and validated in detail by measurements in the Laminar Wind Tunnel of the institute.
The measurements included rear edge noise, detailed boundary layer and turbulence measurements to allow a detailed validation of the calculation model and a study of the noise mechanisms.
In a second focus, the IAG developed an aerodynamically and acoustically optimized profile with a trailing edge flap for use in rotors with active load control. The profile was measured aerodynamically and acoustically for different flap angles in the laminar wind tunnel of the IAG and the improvements compared to the reference profile were shown.

Development of lidar technologies for the recording of wind field structures with regard to the optimisation of wind energy utilisation in mountainous, complex terrain

Lidar Complex

Contact: Dipl.-Ing. Christoph Schulz, Dr.-Ing. Thorsten Lutz

Background and Motivation

Dieses Projekt des süddeutschen Forschungsnetzwerksi "WindForS" hat folgende Ziele: Die Entwicklung von Lidar-Messverfahren für topographisch komplexe Standorte; Entwicklung und Validierung von Windfeldmodellen im komplexen Gelände und ein vertieftes Verständnis des Verhalten von Windenergieanlagen (WEA) im komplexen Gelände. Dazu werden Messungen im flachen und komplexen Gelände durchgeführt, um den Einfluss der Topographie zu bestimmen sowie den Einfluss von tages- und jahreszeitlichen Schwankungen im komplexen Gelände. Des Weiteren werden verschiedene Messmethoden (Windmessmast, meteorologische Messungen mit UAV und Lidar-Systemen) miteinander verglichen. Da Lidar-Systeme eine große Ungenauigkeit im komplexen Gelände aufweisen, sollen Algorithmen entwickelt werden, um die Messgenauigkeit zu erhöhen.

This project of the Southern German research network "WindForS" has the following goals: The development of lidar measurement methods for topographically complex locations; development and validation of wind field models in complex terrain and a deeper understanding of the behaviour of wind turbines in complex terrain. For this purpose, measurements in flat and complex terrain will be performed to determine the influence of topography and the influence of daily and seasonal variations in the complex terrain. Furthermore, different measurement methods (wind mast, meteorological measurements with UAV and lidar systems) will be compared. Since lidar systems show a large inaccuracy in complex terrain, algorithms are to be developed to increase the measurement accuracy.

Objectives and working packages of IAG

  • Modelling and measurement of the complex load in the wind tunnel
  • Simulation of a real wind turbine in IEC compliant terrain
  • Simulation of a generic wind turbine in complex terrain
  • Comparison of different simulation methodologies
  • Evaluation of the load and power behaviour of wind turbines in complex terrain
  • Improvement of the performance or yield forecast



Background of the OWEA LOADs Project

Contact: Pascal Weihing

The objective of the "OWEA Loads" project was to describe the aerodynamic, hydrodynamic and operational loads, in particular of the rotor/nacelle unit, of offshore wind turbines in all their facets. On the one hand, the extensive and cost-intensive load measurements in the first German offshore test field "alpha ventus" as well as their previous processing within the scope of various RAVE projects were further scientifically used. On the other hand, specific questions had to be answered in the further development of future offshore wind turbines. The latter aspect applies in particular to stochastic properties and the characterisation of loads using probabilistic methods. Based on this, various concepts were investigated with regard to possible load reduction through control and integrated design in order to determine the actual service life of an individual plant and thus qualify it for extended operation beyond the design period. With the newly gained knowledge, design conditions for future generations of offshore wind turbines can be derived and specified.

Works at IAG

At the IAG the simulation chain for the calculation of rotor aerodynamics with turbulent inflow was extended to the applicability for wind farms. In addition to the existing fully resolved simulation of the turbines, which represents the highest modelling depth, the so-called Actuator Line Method (ACL) was implemented, qualified for wind farm simulations and used to calculate the interactions between two turbines in "alpha ventus". This method abstracts the flow around the rotor blades and thus considerably reduces the computational effort and the time required for simulation setup and is therefore particularly suitable for the simulation of wake interactions in the wind farm. The method was implemented in the flow solver FLOWer, so that any number of different turbines can be simulated and controlled in the wind farm. The ACL was compared and evaluated with the fully resolved simulation for a single turbine and for the interference of two turbines. Based on the model assumptions, the ACL has uncertainties regarding the load prediction. However, the results of the overrun and its instability correspond well with the fully resolved simulations. The gain in knowledge is characterised by the fact that the ACL is excellently suited to reproduce the flow situation in a wind farm. This makes it possible in the future to reproduce the load behaviour of an individual turbine in the wind farm environment.

Contact: Dipl.-Ing. Alexander Wolf, Dr.-Ing. Thorsten Lutz

Background and Motivation

The objective of this German-Israeli joint project is the application and demonstration of the potential of active flow control (AFC) to reduce the flow-induced noise of the rotors of wind turbines. The noise reduction that can be achieved by active flow control can contribute to increasing the acceptance of on-shore turbines and can be used to increase the performance of future wind turbines by increasing the possible rotor speed. The work in this project concentrates on the reduction of boundary layer induced trailing edge noise, which is the dominant noise source. It was shown that a considerable noise reduction can be achieved by constant, flat extraction. Numerical as well as experimental studies on a NACA64-418 profile with extraction were carried out at the IAG. A noise reduction of up to 6dB could be proven.

Objectives and working packages at IAG

  • Investigation of the influence of different boundary layer parameters on the rear edge noise
  • Numerical simulation of a NACA64-418 profile with surface extraction
  • Aerodynamic and aeroacoustic measurements of a NACA64-418 profile with surface suction at the laminar wind tunnel of the institute

Contact: Dr.-Ing. Thorsten Lutz, Dr.-Ing. Andreas Herrig, Dr.-Ing. Werner Wuerz

In the SIROCCO project, a model for the calculation of trailing edge noise was further developed at IAG and validated on the basis of aeroacoustic measurements in the institute's laminar wind tunnel. The improved calculation method was then used for the combined aerodynamic-acoustic design of blade tip profiles of two commercial wind turbines considered in the project. Compatibility with the inner blade profiles and the ability to be integrated into the blade were considered as limiting boundary conditions.

The new profiles were successfully measured in the Laminar Wind Tunnel and compared to the reference profiles. A noise reduction as well as an increase of the aerodynamic quality could be shown at the same time. In the field test, the new profiles integrated into an existing blade also showed a noise reduction, but this was lower than predicted or measured in the wind tunnel.

In the project DRAW

the basics for an acoustic optimization of wind turbines were developed. In order to achieve this, a substantial improvement or new development of acoustic prediction methods was necessary, taking into account the exact geometry of the wing profiles. This could be achieved for the inflow-turbulence noise, which is caused by the interaction of turbulence with the leading edge of the profile, by coupling acoustic analogy and boundary element methods. The essential result that a thicker leading edge reduces the noise could be impressively confirmed by measurements. Furthermore, the method was extended to compressible basic flows.

In the project DATA

an acoustic optimization of the profile geometry regarding the trailing-edge noise was performed. For this purpose, a prediction method was used which links the state of the turbulent boundary layer at the trailing edge with the sound spectrum. In turn, measurements proved that noise reduction was actually achieved. In a further step, these acoustically optimized profiles were successfully tested on a model wind turbine in the German-Dutch Wind Tunnel (DNW).

LARS - LAst Reductions System

Ansprechpartner: Dipl.-Ing. Levin Klein, Dr.-Ing. Thorsten Lutz

Hintergrund und Problemstellung

Das nationale Forschungsprojekt LARS (Gefördert vom Bundesministerium für Umwelt, Naturschutz und Reaktorsicherheit aufgrund eines Beschlusses des Deutschen Bundestages) ist Teil des Verbundforschungsvorhabes OpTiWi (OpTimierung von Windenergieanlagen). Dieses verfolgt den Ansatz, aus dem Blickwinkel von Betreibern von Windenergieanlagen konkrete Konzepte für Windenergieanlagen mit dem Ziel zu entwickeln, die Kosten der Windenergienutzung weiter zu reduzieren und die Verfügbarkeit von Windenergieanlagen sowie deren Ertrag zu maximieren und diese dann exemplarisch umzusetzen. Die einzelnen Teilprojekte des Vorhabens fokussieren dabei auf die Optimierung von Windenergieanlagen hinsichtlich eines lastarmen Betriebs - Teilprojekt LARS und die Reduktion der Kosten für Montage, Errichtung und Wartung von Windenergieanlagen - Teilprojekt KALOS. Die Teilprojekte sind angeschlossen an den Bau und die Nutzung einer Forschungsplattform in Form einer 3,4 MW Windenergieanlage - Teilprojekt Technologieträger WETEC an der, bzw. mit der die entwickelten Konzepte exemplarisch umgesetzt und getestet werden.
Die Besonderheit der entwickelten Windkraftanlage ist, dass sie im Gegensatz zu den meisten heutzutage errichteten Multimegawatt Anlagen über einen 2-Blatt Rotor verfügt. Dieser bietet wesentliche Vorteile hinsichtlich der Kosten, des Transports und der Errichtung der Windkraftanlage, speziell im komplexen Gelände und in Waldgebieten. Ziel des Projektes ist die Reduktion der erhöhten Fatigue Lasten und Lastschwankungen durch eine gezielte Gestaltung bzw. aktive Regelung neu eingeführter Elastizitäten zwischen Nabenträger und Turbinenträger. Am Projekt sind neben dem IAG der Stiftungslehrstuhl für Windenergie (SWE) der Universität Stuttgart, das DLR Braunschweig und das Unternehmen SkyWind GmbH beteiligt.

Arbeiten am IAG

Die bestehende CFD-basierte Berechnungskette für Windenergieanlagen soll so weiterentwickelt werden, dass der Einfluss der elastischen Kopplung auf die Lasten der Windenergieanlage numerisch untersucht werden kann. Außerdem dienen die durchzuführenden hochaufgelösten Strömungssimulationen der Validierung einfacher im Projekt eingesetzter Aerodynamikcodes (z.B. BEM). Des weiteren werden 2D Strömungssimulationen zur Validierung der in diesen Aerodynamikcodes implementierten Dynamik Stall Vorhersagemodellen durchgeführt.

Detailed simulation of local wind fields in complex terrain and their influence on wind turbines

more about AssiSt


Dr.-Ing. Thorsten Lutz

This image shows Thorsten Lutz

Thorsten Lutz


Head of working group Aircraft Aerodynamics / Head of working group Wind Energy

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