https://sam.ensam.eu:443 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. Sat, 11 Jul 2026 02:25:50 GMT 2026-07-11T02:25:50Z http://hdl.handle.net/10985/8894 Experimental and numerical study of flow around a wind turbine rotor; Etude numérique et expérimentale de l'écoulement autour d'un rotor éolien DOBREV, Ivan; MASSOUH, Fawaz; MEMON, Asif An improved model of an actuator surface is proposed, representing the flow around a wind turbine. This model was developed in conjunction with a Navier-Stokes solver using a blade element method for the calculation of power and wake development. Blades have been replaced with thin surfaces, and a boundary condition of “pressure discontinuity” has been applied with rotor inflow and blade-section characteristics. The proposed improvement consists of applying tangential body forces along the chord, in addition to normal body forces resulting from pressure discontinuity along the blade cross-section. The proposed model has been validated for the flow around a horizontal-axis wind turbine. The results obtained from the proposed model are compared with the experimental results obtained from PIV-wind tunnel techniques. The comparison has displayed the necessity of the proposed model for accurate reproduction of the wake behind rotor. The rapidity of calculation, in comparison to full-geometry modelling, appears to be promising for wind farm simulations.; Un modèle amélioré de surface active est proposé pour représenter l’écoulement autour d'une éolienne. Ce modèle est développé en association avec un solveur Navier-Stokes et en utilisant une méthode d'élément de pale pour le calcul de la puissance de l’éolienne et du développement du sillage. Les pales sont remplacées par des surfaces minces, et une condition limite de "discontinuité de pression" a été appliquée à partir de la vitesse d'entrée dans le rotor et des caractéristiques du profil de pale. L'amélioration proposée consiste à appliquer des forces volumiques tangentielles le long de la corde, en plus des forces volumiques normales résultantes de la discontinuité de pression à travers la surface de la pale. Le modèle proposé a été validé pour l'écoulement autour d'une éolienne à axe horizontal. Les résultats obtenus à partir du modèle proposé sont comparés avec les résultats expérimentaux obtenus en soufflerie par la technique PIV. La comparaison a démontré l’intérêt du modèle proposé pour une bonne reproduction du sillage derrière le rotor. La rapidité de calcul, par rapport à la simulation d’une géométrie complète des pales, semble promettant pour des simulations de parcs éoliens. Tue, 01 Jan 2013 00:00:00 GMT http://hdl.handle.net/10985/8894 2013-01-01T00:00:00Z DOBREV, Ivan MASSOUH, Fawaz MEMON, Asif An improved model of an actuator surface is proposed, representing the flow around a wind turbine. This model was developed in conjunction with a Navier-Stokes solver using a blade element method for the calculation of power and wake development. Blades have been replaced with thin surfaces, and a boundary condition of “pressure discontinuity” has been applied with rotor inflow and blade-section characteristics. The proposed improvement consists of applying tangential body forces along the chord, in addition to normal body forces resulting from pressure discontinuity along the blade cross-section. The proposed model has been validated for the flow around a horizontal-axis wind turbine. The results obtained from the proposed model are compared with the experimental results obtained from PIV-wind tunnel techniques. The comparison has displayed the necessity of the proposed model for accurate reproduction of the wake behind rotor. The rapidity of calculation, in comparison to full-geometry modelling, appears to be promising for wind farm simulations. Un modèle amélioré de surface active est proposé pour représenter l’écoulement autour d'une éolienne. Ce modèle est développé en association avec un solveur Navier-Stokes et en utilisant une méthode d'élément de pale pour le calcul de la puissance de l’éolienne et du développement du sillage. Les pales sont remplacées par des surfaces minces, et une condition limite de "discontinuité de pression" a été appliquée à partir de la vitesse d'entrée dans le rotor et des caractéristiques du profil de pale. L'amélioration proposée consiste à appliquer des forces volumiques tangentielles le long de la corde, en plus des forces volumiques normales résultantes de la discontinuité de pression à travers la surface de la pale. Le modèle proposé a été validé pour l'écoulement autour d'une éolienne à axe horizontal. Les résultats obtenus à partir du modèle proposé sont comparés avec les résultats expérimentaux obtenus en soufflerie par la technique PIV. La comparaison a démontré l’intérêt du modèle proposé pour une bonne reproduction du sillage derrière le rotor. La rapidité de calcul, par rapport à la simulation d’une géométrie complète des pales, semble promettant pour des simulations de parcs éoliens. http://hdl.handle.net/10985/11888 Approach for numerical modeling of airfoil dynamic stall VELKOVA, Cvetelina; DOBREV, Ivan; TODOROV, Michael; MASSOUH, Fawaz The aim of the computational study is to present different approach for numerical modeling of airfoil dynamic stall as the airfoil is pitched at a constant rate from zero incidences to a high angle of attack. An application of the Detached-Eddy Simulation model on a NACA 0012 airfoil is presented. The DES model is a method for predicting turbulence in CFD computations, which combines a Reynolds Averaged Navier-Stokes (RANS) method in the boundary layer with a Large Eddy Simulation (LES) in the free shear flow. (DES) turbulence model gives a good accuracy of the flow field because its solves an additional equation for turbulent Reynolds number in a shear stress transport version (SST), which solves a first equation for the turbulent energy K and a second equation for the specific turbulent dissipation rate w. The approach using DES turbulence model is effective because it gives better visualization of flow field, the unsteady separation flow and vortex shedding. Consequently the suggested approach is suitable and it can be used in prediction of dynamic stall phenomenon in the stage of helicopter rotors, wind turbine rotors and aircraft wings design purposes. http://e-university.tu-sofia.bg/e-publ/files/882_BulTrans_12_Velkova.pdf Sun, 01 Jan 2012 00:00:00 GMT http://hdl.handle.net/10985/11888 2012-01-01T00:00:00Z VELKOVA, Cvetelina DOBREV, Ivan TODOROV, Michael MASSOUH, Fawaz The aim of the computational study is to present different approach for numerical modeling of airfoil dynamic stall as the airfoil is pitched at a constant rate from zero incidences to a high angle of attack. An application of the Detached-Eddy Simulation model on a NACA 0012 airfoil is presented. The DES model is a method for predicting turbulence in CFD computations, which combines a Reynolds Averaged Navier-Stokes (RANS) method in the boundary layer with a Large Eddy Simulation (LES) in the free shear flow. (DES) turbulence model gives a good accuracy of the flow field because its solves an additional equation for turbulent Reynolds number in a shear stress transport version (SST), which solves a first equation for the turbulent energy K and a second equation for the specific turbulent dissipation rate w. The approach using DES turbulence model is effective because it gives better visualization of flow field, the unsteady separation flow and vortex shedding. Consequently the suggested approach is suitable and it can be used in prediction of dynamic stall phenomenon in the stage of helicopter rotors, wind turbine rotors and aircraft wings design purposes. http://hdl.handle.net/10985/17996 Experimental and numerical analysis of a novel Darrieus rotor with variable pitch mechanism at low TSR ZOUZOU, B.; DOBREV, Ivan; MASSOUH, Fawaz; DIZENE, Rabah The Darrieus vertical axis wind-turbine (VAWT) has been the subject of numerous recent studies aimed at improving its aerodynamic performance in order to locate it in urban areas. This article is devoted to the study of an original VAWT with variable-pitch and low tip speed ratio TSR which is favorable to noise reduction and can operate at low velocity wind. The aerodynamic performance of this turbine is studied experimentally in wind tunnel as well as by CFD. In order to obtain the 3D-flow field around the wind turbine rotor, the numerical simulations are performed by means of detached eddy simulation method (DES). The simulation of pitch variation is made possible by using sliding-mesh method. Thus a specially created program adapts the pitch depending on the blade azimuthal position during rotation. The obtained results show that adapted pitch blades are preferable because they permit to obtain a power coefficient Cp that rivals other VAWT in the case of . The maximum torque fluctuation during rotation is lower in the case of adapted variable-pitch compared to fixed-pitch and thus the maximum aerodynamic loads on the structure can be reduced. Moreover, the pitch adaptation leads to lower interaction effects between the upstream-blade wake and down-stream blades. Tue, 01 Jan 2019 00:00:00 GMT http://hdl.handle.net/10985/17996 2019-01-01T00:00:00Z ZOUZOU, B. DOBREV, Ivan MASSOUH, Fawaz DIZENE, Rabah The Darrieus vertical axis wind-turbine (VAWT) has been the subject of numerous recent studies aimed at improving its aerodynamic performance in order to locate it in urban areas. This article is devoted to the study of an original VAWT with variable-pitch and low tip speed ratio TSR which is favorable to noise reduction and can operate at low velocity wind. The aerodynamic performance of this turbine is studied experimentally in wind tunnel as well as by CFD. In order to obtain the 3D-flow field around the wind turbine rotor, the numerical simulations are performed by means of detached eddy simulation method (DES). The simulation of pitch variation is made possible by using sliding-mesh method. Thus a specially created program adapts the pitch depending on the blade azimuthal position during rotation. The obtained results show that adapted pitch blades are preferable because they permit to obtain a power coefficient Cp that rivals other VAWT in the case of . The maximum torque fluctuation during rotation is lower in the case of adapted variable-pitch compared to fixed-pitch and thus the maximum aerodynamic loads on the structure can be reduced. Moreover, the pitch adaptation leads to lower interaction effects between the upstream-blade wake and down-stream blades. http://hdl.handle.net/10985/17839 COMPUTATIONALLY INEXPENSIVE FREE VORTEX METHOD TO OBTAIN VORTEX CORE POSITION IN THE WAKE OF A HORIZONTAL AXIS WIND TURBINE MEGHLAOUI, Issam; DOBREV, Ivan; MASSOUH, Fawaz; BENRETEM, A. Ouahab; KHALFA, Dalila This work aims to develop a free wake model, allowing quick simulation of flow through a horizontal axis wind turbine. The rapidity of computation is particularly interesting when this aerodynamic model is integrated with complementary mechanical and electrical models in order to study the unsteady behavior of the complete chain of energy transfer in the wind turbine. The proposed model takes into account both the tangential and longitudinal vorticity of the vortex system formed behind the rotor. The employed vortex system replaces the helical wake close to the wind turbine by a series of vortex rings and the far wake by a semi-infinite vortex cylinder. By taking into account the root vortex, the proposed model is used to study the development of the near wake of a horizontal axis wind turbine for different speeds of rotation. The shape of the near wake as well as the position of the trailing vortices are compared with particle image velocimetry experimental results for a low-power wind turbine tested in the wind tunnel of Arts et Métiers-ParisTech. The model shows a good agreement between the calculation and the experience. Sun, 01 Jan 2017 00:00:00 GMT http://hdl.handle.net/10985/17839 2017-01-01T00:00:00Z MEGHLAOUI, Issam DOBREV, Ivan MASSOUH, Fawaz BENRETEM, A. Ouahab KHALFA, Dalila This work aims to develop a free wake model, allowing quick simulation of flow through a horizontal axis wind turbine. The rapidity of computation is particularly interesting when this aerodynamic model is integrated with complementary mechanical and electrical models in order to study the unsteady behavior of the complete chain of energy transfer in the wind turbine. The proposed model takes into account both the tangential and longitudinal vorticity of the vortex system formed behind the rotor. The employed vortex system replaces the helical wake close to the wind turbine by a series of vortex rings and the far wake by a semi-infinite vortex cylinder. By taking into account the root vortex, the proposed model is used to study the development of the near wake of a horizontal axis wind turbine for different speeds of rotation. The shape of the near wake as well as the position of the trailing vortices are compared with particle image velocimetry experimental results for a low-power wind turbine tested in the wind tunnel of Arts et Métiers-ParisTech. The model shows a good agreement between the calculation and the experience. http://hdl.handle.net/10985/18121 Small wind turbine augmentation: Experimental investigations of shrouded- and twin-rotor wind turbine systems LIPIAN, Michal; DOBREV, Ivan; KARCZEWSKI, Maciej; MASSOUH, Fawaz; JOZWIK, Krzysztof An increase in the efficiency of Small Wind Turbines (SWTs) by aerodynamic optimisation of the blade geometry is limited (low Reynolds number influence). Solutions such as the Diffuser-Augmented Wind Turbine (DAWT) and the twin-rotor systems are of increasing interest. A diffuser promotes an increase in the wind mass flow rate through the turbine, whereas an auxiliary rotor enables extraction of the wind kinetic energy in the wake. The paper summarizes the measurements of wind turbine systems performance conducted at the Institute of Turbomachinery, Lodz University of Technology (IMP TUL). The research incorporated a spectrum of wind turbine configurations for open and shrouded, single- and twin-rotor systems. The objective was to compare the performance of the same rotor in different configurations. The influence of a low Reynolds number flow on the rotor performance is also discussed and quantified. The study shows that, while augmenting the wind turbine performance (as much as twofold increase), shrouding rises significantly the rotor loading. A remedy for that may be an application of the second rotor. Although it provides a rather modest efficiency increase (11–13% for the unshrouded-, 4–5% for shrouded turbine), it allows loads to be distributed more evenly on turbines. Tue, 01 Jan 2019 00:00:00 GMT http://hdl.handle.net/10985/18121 2019-01-01T00:00:00Z LIPIAN, Michal DOBREV, Ivan KARCZEWSKI, Maciej MASSOUH, Fawaz JOZWIK, Krzysztof An increase in the efficiency of Small Wind Turbines (SWTs) by aerodynamic optimisation of the blade geometry is limited (low Reynolds number influence). Solutions such as the Diffuser-Augmented Wind Turbine (DAWT) and the twin-rotor systems are of increasing interest. A diffuser promotes an increase in the wind mass flow rate through the turbine, whereas an auxiliary rotor enables extraction of the wind kinetic energy in the wake. The paper summarizes the measurements of wind turbine systems performance conducted at the Institute of Turbomachinery, Lodz University of Technology (IMP TUL). The research incorporated a spectrum of wind turbine configurations for open and shrouded, single- and twin-rotor systems. The objective was to compare the performance of the same rotor in different configurations. The influence of a low Reynolds number flow on the rotor performance is also discussed and quantified. The study shows that, while augmenting the wind turbine performance (as much as twofold increase), shrouding rises significantly the rotor loading. A remedy for that may be an application of the second rotor. Although it provides a rather modest efficiency increase (11–13% for the unshrouded-, 4–5% for shrouded turbine), it allows loads to be distributed more evenly on turbines. http://hdl.handle.net/10985/8928 Investigation of wind turbine flow and wake MASSOUH, Fawaz; DOBREV, Ivan This paper is dedicated to the investigation and analysis of wind turbine wake. An experimental work is undertaken in wind tunnel on a horizontal axis wind turbine model. The velocity field in the wake is measured using PIV with phase synchronization in order to relate velocity and vortices to the rotating blades. The tip vortices are investigated in successive azimuthal positions of the rotor. A specially developed algorithm based on the circulation maximum detects the positions of the vortex cores and permits to use conditional averaging technique. The analysis of obtained velocity fields enables to determine the vortex core diameter, the swirl velocity distribution and the vortex diffusion as functions of the vortex age. The quality of obtained results permits to use them as reference for the validation of numerical computations. Wed, 01 Jan 2014 00:00:00 GMT http://hdl.handle.net/10985/8928 2014-01-01T00:00:00Z MASSOUH, Fawaz DOBREV, Ivan This paper is dedicated to the investigation and analysis of wind turbine wake. An experimental work is undertaken in wind tunnel on a horizontal axis wind turbine model. The velocity field in the wake is measured using PIV with phase synchronization in order to relate velocity and vortices to the rotating blades. The tip vortices are investigated in successive azimuthal positions of the rotor. A specially developed algorithm based on the circulation maximum detects the positions of the vortex cores and permits to use conditional averaging technique. The analysis of obtained velocity fields enables to determine the vortex core diameter, the swirl velocity distribution and the vortex diffusion as functions of the vortex age. The quality of obtained results permits to use them as reference for the validation of numerical computations. http://hdl.handle.net/10985/8925 Determination of wind turbine far wake using actuator disk AMER, Rodeyna; DOBREV, Ivan; MASSOUH, Fawaz The growth in size of wind turbines over the last years is significant. The rotor diameter becomes somehow comparable to atmospheric boundary layer at the land surface. In this case the assumption of uniform velocity of upcoming wind cannot be valid. The aim of this paper is to create a simplified model of wind turbine rotor which can represent the aerodynamic inter-action of atmospheric boundary layer with a horizontal axis wind turbine. Such model will be also useful for the study of optimal placement of wind turbines in a wind farm when a large number of calculations is needed and when the time required for full CFD calculations be-comes prohibitive. In this study we adopt actuator disk model which takes in account with sufficient precision the influence of blade geometry on wind turbine aerodynamic performance. The proposed actuator disk model is tested in the case of horizontal axis wind turbine using wall-modelled large eddy simulation. The obtained results of aerodynamic performance and wake show the rapidity of calculation and the reliability of proposed approach. Wed, 01 Jan 2014 00:00:00 GMT http://hdl.handle.net/10985/8925 2014-01-01T00:00:00Z AMER, Rodeyna DOBREV, Ivan MASSOUH, Fawaz The growth in size of wind turbines over the last years is significant. The rotor diameter becomes somehow comparable to atmospheric boundary layer at the land surface. In this case the assumption of uniform velocity of upcoming wind cannot be valid. The aim of this paper is to create a simplified model of wind turbine rotor which can represent the aerodynamic inter-action of atmospheric boundary layer with a horizontal axis wind turbine. Such model will be also useful for the study of optimal placement of wind turbines in a wind farm when a large number of calculations is needed and when the time required for full CFD calculations be-comes prohibitive. In this study we adopt actuator disk model which takes in account with sufficient precision the influence of blade geometry on wind turbine aerodynamic performance. The proposed actuator disk model is tested in the case of horizontal axis wind turbine using wall-modelled large eddy simulation. The obtained results of aerodynamic performance and wake show the rapidity of calculation and the reliability of proposed approach. http://hdl.handle.net/10985/8899 Investigation of relationship between drag and lift coefficients for a generic car model DOBREV, Ivan; MASSOUH, Fawaz The paper presents a study of aerodynamic characteristics of a car, which has the simplified geometric shape, so called Ahmed body. Flow around the body and the influence of its rear slant angle on drag are widely studied by numerous researchers. However, small number of studies treats the relationship between drag and lift and this phenomenon is not fully understood. To clarify the relationship between lift and drag, experiments are conducted in the wind tunnel of ENSAM - Paris. The study is carried out for different rear slant angles in order to determine how the drag coefficient varies with lift. The results of experiments are completed by numerical simulations, which permit to obtain the detailed flow field around Ahmed body and to understand better the effect of rear slant angle on drag and lift coefficients. Wed, 01 Jan 2014 00:00:00 GMT http://hdl.handle.net/10985/8899 2014-01-01T00:00:00Z DOBREV, Ivan MASSOUH, Fawaz The paper presents a study of aerodynamic characteristics of a car, which has the simplified geometric shape, so called Ahmed body. Flow around the body and the influence of its rear slant angle on drag are widely studied by numerous researchers. However, small number of studies treats the relationship between drag and lift and this phenomenon is not fully understood. To clarify the relationship between lift and drag, experiments are conducted in the wind tunnel of ENSAM - Paris. The study is carried out for different rear slant angles in order to determine how the drag coefficient varies with lift. The results of experiments are completed by numerical simulations, which permit to obtain the detailed flow field around Ahmed body and to understand better the effect of rear slant angle on drag and lift coefficients. http://hdl.handle.net/10985/21360 Innovative design method and experimental investigation of a small-scale and very low tip-speed ratio wind turbine BOURHIS, Martin; PEREIRA, Michaël; DOBREV, Ivan; RAVELET, Florent Small horizontal axis wind turbines operating at low wind speeds face the issue of low performance compared to large wind turbines. A high amount of torque is required to start producing power at low wind speed to overtake friction of mechanical parts. A low design tip-speed ratio (λ) is suitable for low power applications. The relevance of the classical blade-element/ momentum theory, traditionally used for the design of large wind turbines operating at high tip-speed ratio, is controversial at low tip-speed ratio. This paper presents a new design methodology for a 300 mm horizontal axis wind turbine operating at very low tip-speed ratio. Chord and blade angle distributions were computed by applying the Euler’s turbomachinery theorem. The new wind turbine has multiple fan-type blades and a high solidity. The rotor was tested in wind tunnel. The power and torque coefficients have been measured, and the velocities in the wake have been explored by stereoscopic particle image velocimetry. The results are compared to a conventional 3-bladed horizontal axis wind turbine operating at higher tip-speed ratio λ = 3. The new wind turbine achieves a maximum power coefficient of 0.31 for λ = 1. The conventional wind turbine achieves similar performance. At low tip-speed ratio, the torque coefficient (Cτ) is higher for the new wind turbine than for the conventional one and decreases linearly with the tip-speed ratio. The high magnitude of torque at low tip-speed ratio allows it to have lower instantaneous cut-in wind speed (2.4 m.s−1) than the conventional wind turbine (7.9 m.s−1). The order of magnitude of the axial and tangential velocities in the near wake are closed to the design requirements. The current method could still be improved in order to better predict the profiles. The analysis of the wake shows that the new wind turbine induces a highly stable and rotating wake, with lower wake expansion and deceleration than the conventional one. This could be useful to drive a contra-rotating rotor. Fri, 01 Jan 2021 00:00:00 GMT http://hdl.handle.net/10985/21360 2021-01-01T00:00:00Z BOURHIS, Martin PEREIRA, Michaël DOBREV, Ivan RAVELET, Florent Small horizontal axis wind turbines operating at low wind speeds face the issue of low performance compared to large wind turbines. A high amount of torque is required to start producing power at low wind speed to overtake friction of mechanical parts. A low design tip-speed ratio (λ) is suitable for low power applications. The relevance of the classical blade-element/ momentum theory, traditionally used for the design of large wind turbines operating at high tip-speed ratio, is controversial at low tip-speed ratio. This paper presents a new design methodology for a 300 mm horizontal axis wind turbine operating at very low tip-speed ratio. Chord and blade angle distributions were computed by applying the Euler’s turbomachinery theorem. The new wind turbine has multiple fan-type blades and a high solidity. The rotor was tested in wind tunnel. The power and torque coefficients have been measured, and the velocities in the wake have been explored by stereoscopic particle image velocimetry. The results are compared to a conventional 3-bladed horizontal axis wind turbine operating at higher tip-speed ratio λ = 3. The new wind turbine achieves a maximum power coefficient of 0.31 for λ = 1. The conventional wind turbine achieves similar performance. At low tip-speed ratio, the torque coefficient (Cτ) is higher for the new wind turbine than for the conventional one and decreases linearly with the tip-speed ratio. The high magnitude of torque at low tip-speed ratio allows it to have lower instantaneous cut-in wind speed (2.4 m.s−1) than the conventional wind turbine (7.9 m.s−1). The order of magnitude of the axial and tangential velocities in the near wake are closed to the design requirements. The current method could still be improved in order to better predict the profiles. The analysis of the wake shows that the new wind turbine induces a highly stable and rotating wake, with lower wake expansion and deceleration than the conventional one. This could be useful to drive a contra-rotating rotor. http://hdl.handle.net/10985/8967 Experimental study of yawed inflow around wind turbine rotor NOURA, Belkheir; DOBREV, Ivan; DIZENE, Rabah; MASSOUH, Fawaz; KHELLADI, Sofiane In this article, we present an experimental study in a wind tunnel of a three-bladed, Rutland 503 model, horizontal axis yawed wind turbine. Power measurement and an exploration downstream wake of the turbine using particle image velocimetry measurements are performed. The variation of power coefficient as a function of rotational velocity is presented for different yaw angles. The results show a loss of power from the wind turbine when the yaw angle increases. The velocity field of the downstream wake of the rotor is presented in an azimuth plane, which passes through the symmetry axis of the rotor. The instantaneous velocity field is measured and recorded to allow for obtaining the averaged velocity field. The results also show variations in the wake downstream due to decelerating flow caused by the yawed turbine rotor. Analysis of this data shows that the active control of yaw angles could be an advantage to preserve the power from the wind turbine and that details near rotor wake are important for wake theories and topredict the performance of wind turbines as well. Sun, 01 Jan 2012 00:00:00 GMT http://hdl.handle.net/10985/8967 2012-01-01T00:00:00Z NOURA, Belkheir DOBREV, Ivan DIZENE, Rabah MASSOUH, Fawaz KHELLADI, Sofiane In this article, we present an experimental study in a wind tunnel of a three-bladed, Rutland 503 model, horizontal axis yawed wind turbine. Power measurement and an exploration downstream wake of the turbine using particle image velocimetry measurements are performed. The variation of power coefficient as a function of rotational velocity is presented for different yaw angles. The results show a loss of power from the wind turbine when the yaw angle increases. The velocity field of the downstream wake of the rotor is presented in an azimuth plane, which passes through the symmetry axis of the rotor. The instantaneous velocity field is measured and recorded to allow for obtaining the averaged velocity field. The results also show variations in the wake downstream due to decelerating flow caused by the yawed turbine rotor. Analysis of this data shows that the active control of yaw angles could be an advantage to preserve the power from the wind turbine and that details near rotor wake are important for wake theories and topredict the performance of wind turbines as well.