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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 GMThttp://hdl.handle.net/10985/89282014-01-01T00:00:00ZMASSOUH, FawazDOBREV, IvanThis 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.Determination of wind turbine far wake using actuator disk
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 GMThttp://hdl.handle.net/10985/89252014-01-01T00:00:00ZAMER, RodeynaDOBREV, IvanMASSOUH, FawazThe 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.Experimental study of yawed inflow around wind turbine 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 GMThttp://hdl.handle.net/10985/89672012-01-01T00:00:00ZNOURA, BelkheirDOBREV, IvanDIZENE, RabahMASSOUH, FawazKHELLADI, SofianeIn 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.Bioinspired turbine blades offer new perspectives for wind energy
http://hdl.handle.net/10985/11774
Bioinspired turbine blades offer new perspectives for wind energy
COGNET, Vincent; COURRECH DU PONT, Sylvain; DOBREV, Ivan; MASSOUH, Fawaz; THIRIA, Benjamin
Wind energy is becoming a significant alternative solution for future energy production. Modern turbines now benefit from engineering expertise, and a large variety of different models exists, depending on the context and needs. However, classical wind turbines are designed to operate within a narrow zone centred around their optimal working point. This limitation prevents the use of sites with variable wind to harvest energy, involving significant energetic and economic losses. Here, we present a new type of bioinspired wind turbine using elastic blades, which passively deform through the air loading and centrifugal effects. This work is inspired from recent studies on insect flight and plant reconfiguration, which show the ability of elastic wings or leaves to adapt to the wind conditions and thereby to optimize performance. We show that in the context of energy production, the reconfiguration of the elastic blades significantly extends the range of operating regimes using only passive, non-consuming mechanisms. The versatility of the new turbine model leads to a large increase of the converted energy rate, up to 35%. The fluid/elasticity mechanisms involved for the reconfiguration capability of the new blades are analysed in detail, using experimental observations and modelling.
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/10985/117742017-01-01T00:00:00ZCOGNET, VincentCOURRECH DU PONT, SylvainDOBREV, IvanMASSOUH, FawazTHIRIA, BenjaminWind energy is becoming a significant alternative solution for future energy production. Modern turbines now benefit from engineering expertise, and a large variety of different models exists, depending on the context and needs. However, classical wind turbines are designed to operate within a narrow zone centred around their optimal working point. This limitation prevents the use of sites with variable wind to harvest energy, involving significant energetic and economic losses. Here, we present a new type of bioinspired wind turbine using elastic blades, which passively deform through the air loading and centrifugal effects. This work is inspired from recent studies on insect flight and plant reconfiguration, which show the ability of elastic wings or leaves to adapt to the wind conditions and thereby to optimize performance. We show that in the context of energy production, the reconfiguration of the elastic blades significantly extends the range of operating regimes using only passive, non-consuming mechanisms. The versatility of the new turbine model leads to a large increase of the converted energy rate, up to 35%. The fluid/elasticity mechanisms involved for the reconfiguration capability of the new blades are analysed in detail, using experimental observations and modelling.Investigation of the Rotor Wake of Horizontal Axis Wind Turbine under Yawed Condition
http://hdl.handle.net/10985/11715
Investigation of the Rotor Wake of Horizontal Axis Wind Turbine under Yawed Condition
NOURA, Belhadj; DOBREV, Ivan; KERFAH, R.; MASSOUH, Fawaz; KHELLADI, Sofiane
The wake and the lack of existing velocity behind the wind turbine affect the energy production and the mechanical integrity of wind turbines downstream in the wind farms. This paper presents an investigation of the unsteady flow around a wind turbine under yawed condition. The simulations and experimental measures are made for the yaw angle rotor 30° and 0°. The wind velocity is 9.3 m/s and the rotation velocity rotor of the wind turbine in 1300, 1500 and 1800 rpm. The wind turbine rotor which is modeled is of a commercial wind turbine i.e. Rutland 503. The approach Improved Delayed Detached Eddy Simulation (IDDES) based on the SST turbulence model is used in the modeling of the flow. The solutions are obtained by using the solver which uses finite volume method. The particle image velocimetry (PIV) method is used in wind tunnel measurements in the experimental laboratory of the ENSAM Paris-Tech. The yawed downstream wake of the rotor is compared with that obtained by the experimental measurements. The results illustrate perfectly the development of the near and far wake of the rotor operation. It is observed that the upstream wind turbine yawed will have a positive impact on the power of the downstream turbine due the distance reduction of the downstream wake of the wind turbine. However the power losses are important for yawed wind turbine when compared with the wind turbine without yaw. The improved understanding of the unsteady environmental of the Horizontal Axis wind Turbine allows optimizing wind turbine structures and the number of wind turbines in wind farms.
Fri, 01 Jan 2016 00:00:00 GMThttp://hdl.handle.net/10985/117152016-01-01T00:00:00ZNOURA, BelhadjDOBREV, IvanKERFAH, R.MASSOUH, FawazKHELLADI, SofianeThe wake and the lack of existing velocity behind the wind turbine affect the energy production and the mechanical integrity of wind turbines downstream in the wind farms. This paper presents an investigation of the unsteady flow around a wind turbine under yawed condition. The simulations and experimental measures are made for the yaw angle rotor 30° and 0°. The wind velocity is 9.3 m/s and the rotation velocity rotor of the wind turbine in 1300, 1500 and 1800 rpm. The wind turbine rotor which is modeled is of a commercial wind turbine i.e. Rutland 503. The approach Improved Delayed Detached Eddy Simulation (IDDES) based on the SST turbulence model is used in the modeling of the flow. The solutions are obtained by using the solver which uses finite volume method. The particle image velocimetry (PIV) method is used in wind tunnel measurements in the experimental laboratory of the ENSAM Paris-Tech. The yawed downstream wake of the rotor is compared with that obtained by the experimental measurements. The results illustrate perfectly the development of the near and far wake of the rotor operation. It is observed that the upstream wind turbine yawed will have a positive impact on the power of the downstream turbine due the distance reduction of the downstream wake of the wind turbine. However the power losses are important for yawed wind turbine when compared with the wind turbine without yaw. The improved understanding of the unsteady environmental of the Horizontal Axis wind Turbine allows optimizing wind turbine structures and the number of wind turbines in wind farms.Investigation of relationship between drag and lift coefficients for a generic car model
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 GMThttp://hdl.handle.net/10985/88992014-01-01T00:00:00ZDOBREV, IvanMASSOUH, FawazThe 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.Experimental and numerical study of flow around a wind turbine rotor
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 GMThttp://hdl.handle.net/10985/88942013-01-01T00:00:00ZDOBREV, IvanMASSOUH, FawazMEMON, AsifAn 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.Approach for numerical modeling of airfoil dynamic stall
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 GMThttp://hdl.handle.net/10985/118882012-01-01T00:00:00ZVELKOVA, CvetelinaDOBREV, IvanTODOROV, MichaelMASSOUH, FawazThe 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.Experimental and numerical analysis of a novel Darrieus rotor with variable pitch mechanism at low TSR
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 GMThttp://hdl.handle.net/10985/179962019-01-01T00:00:00ZZOUZOU, B.DOBREV, IvanMASSOUH, FawazDIZENE, RabahThe 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.NUMERICAL MODELING OF UNSTABLE FLOWS IN CONDUCTS WITH VARIABLE GEOMETRY
http://hdl.handle.net/10985/17784
NUMERICAL MODELING OF UNSTABLE FLOWS IN CONDUCTS WITH VARIABLE GEOMETRY
RAMOUL, Sami; FOURAR, Ali; MASSOUH, Fawaz
Changes in the system flow of a fluid in a conduct often cause sudden changes in pressure and give rise to so-called unstable flows. So, the study of the phenomenon of unstable flows aims to determine ifthe pressure in a system is within the prescribed limits, following a perturbation of the flow. In the objective of studying the rangeof a water hammer, an examination of variations in velocity or flow and pressure resulting from inappropriate operation of the hydraulic system is made. This study presents a numerical modeling of the phenomenon of instable flows in load conducts with variable geometries. The characteristic method is used to solve the governing equations. Thanks to the AFT Impulse industrial program, very interesting and very practical numerical resultsare obtainedto describe the phenomenon of instable flows inconducts with variable geometry. And to more illustrate the graphical presentation two cases are graphically overlay for each of the two types of models (slow closing and rapid closingof the valve).
Mon, 01 Jan 2018 00:00:00 GMThttp://hdl.handle.net/10985/177842018-01-01T00:00:00ZRAMOUL, SamiFOURAR, AliMASSOUH, FawazChanges in the system flow of a fluid in a conduct often cause sudden changes in pressure and give rise to so-called unstable flows. So, the study of the phenomenon of unstable flows aims to determine ifthe pressure in a system is within the prescribed limits, following a perturbation of the flow. In the objective of studying the rangeof a water hammer, an examination of variations in velocity or flow and pressure resulting from inappropriate operation of the hydraulic system is made. This study presents a numerical modeling of the phenomenon of instable flows in load conducts with variable geometries. The characteristic method is used to solve the governing equations. Thanks to the AFT Impulse industrial program, very interesting and very practical numerical resultsare obtainedto describe the phenomenon of instable flows inconducts with variable geometry. And to more illustrate the graphical presentation two cases are graphically overlay for each of the two types of models (slow closing and rapid closingof the valve).