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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.Modelling surface tension with smoothed particle hydrodynamics in reactive rotational moulding
http://hdl.handle.net/10985/9903
Modelling surface tension with smoothed particle hydrodynamics in reactive rotational moulding
HAMIDI, A; KHELLADI, Sofiane; ILLOUL, Lounès; SHIRINBAYAN, Mohammadali; BAKIR, Farid; TCHARKHTCHI, Abbas
Reactive Rotational Moulding (RRM) is the best process for producing large hollow plastic parts without weld lines. Constant quality in technical parts requires the process to be mastered by controlling on-line the main physical phenomena. However, the main drawback of RRM is poor control of the process due to the high number of influent parameters. In these conditions, the optimization of the process is quite complex. The aim of this work is to simulate the reactive fluid flow during RRM with Smoothed Particle Hydrodynamics (SPH) solver in two dimensions (2D) and three dimensions (3D) taking into account surface tension force. To implement this force, the interface is tracked explicitly using algorithm developed by Barecasco et al. (2013) and Terissa et al. (2013) and the reconstruction of curve or surface boundary by different interpolation or surface construction technique with Lagrangian interpolation and fitting circle methods in 2D and spherical regression in 3D, respectively.
Thu, 01 Jan 2015 00:00:00 GMThttp://hdl.handle.net/10985/99032015-01-01T00:00:00ZHAMIDI, AKHELLADI, SofianeILLOUL, LounèsSHIRINBAYAN, MohammadaliBAKIR, FaridTCHARKHTCHI, AbbasReactive Rotational Moulding (RRM) is the best process for producing large hollow plastic parts without weld lines. Constant quality in technical parts requires the process to be mastered by controlling on-line the main physical phenomena. However, the main drawback of RRM is poor control of the process due to the high number of influent parameters. In these conditions, the optimization of the process is quite complex. The aim of this work is to simulate the reactive fluid flow during RRM with Smoothed Particle Hydrodynamics (SPH) solver in two dimensions (2D) and three dimensions (3D) taking into account surface tension force. To implement this force, the interface is tracked explicitly using algorithm developed by Barecasco et al. (2013) and Terissa et al. (2013) and the reconstruction of curve or surface boundary by different interpolation or surface construction technique with Lagrangian interpolation and fitting circle methods in 2D and spherical regression in 3D, respectively.POD study of aerated cavitation in a venturi nozzle
http://hdl.handle.net/10985/10296
POD study of aerated cavitation in a venturi nozzle
TOMOV, Petar; DANLOS, Amélie; KHELLADI, Sofiane; RAVELET, Florent; SARRAF, Christophe; BAKIR, Farid
The fact of injecting bubbles into a cavitating flow influences typical cavitating behavior. Cavitation and aerated cavitation experiments has been carried out on a symmetrical venturi nozzle with convergent/divergent angles of 18 ◦ and 8 ◦ , respectively. A snapshot Proper Orthogonal Decomposition (POD) technique is used to identify different modes in terms of discharge flow velocity, pressure and injected quantity of air. The energy spectrum per given mode is also presented. The first four modes are outlined in the present paper for an aerated and non-aerated cavitating flows.
Thu, 01 Jan 2015 00:00:00 GMThttp://hdl.handle.net/10985/102962015-01-01T00:00:00ZTOMOV, PetarDANLOS, AmélieKHELLADI, SofianeRAVELET, FlorentSARRAF, ChristopheBAKIR, FaridThe fact of injecting bubbles into a cavitating flow influences typical cavitating behavior. Cavitation and aerated cavitation experiments has been carried out on a symmetrical venturi nozzle with convergent/divergent angles of 18 ◦ and 8 ◦ , respectively. A snapshot Proper Orthogonal Decomposition (POD) technique is used to identify different modes in terms of discharge flow velocity, pressure and injected quantity of air. The energy spectrum per given mode is also presented. The first four modes are outlined in the present paper for an aerated and non-aerated cavitating flows.Simulation of Polymer Flow Using Smoothed Particle Hydrodynamics Method
http://hdl.handle.net/10985/8058
Simulation of Polymer Flow Using Smoothed Particle Hydrodynamics Method
RIVIERE, Sylvain; KHELLADI, Sofiane; FARZANEH, Sedigheh; BAKIR, Farid; TCHARKHTCHI, Abbas
Reactive rotational molding (RRM) is a process to manufacture hollow plastic articles. Comparing to rotational molding of thermoplastics, it decreases the process cycle time due to the reactivity of the system. However, the number of influent parameters is relatively high and optimization of the process is complex. During RRM, the viscosity is one of the key parameters and varies according to the polymer molecular weight due to chemical reactions. Simulation is a way to optimize this process. Prediction of the reactive flow is of great interest to optimize process conditions and wall thickness distribution of the molded part. We developed a solver based on smoothed particle hydrodynamics method. This Lagrangian meshfree method is well adapted to simulate free surface flows like those occurring in RRM. First, we validated the code comparing the simulation results to analytical Couette flow solution and experimental measurements of dam break problem. Then, we performed two-dimensional (2D) and 3D simulations to observe the influence of the change of viscosity on the flow, due to the chemical reactions. Adhesion of the polymer on the mold surface is modeled by new boundary conditions.
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/10985/80582013-01-01T00:00:00ZRIVIERE, SylvainKHELLADI, SofianeFARZANEH, SedighehBAKIR, FaridTCHARKHTCHI, AbbasReactive rotational molding (RRM) is a process to manufacture hollow plastic articles. Comparing to rotational molding of thermoplastics, it decreases the process cycle time due to the reactivity of the system. However, the number of influent parameters is relatively high and optimization of the process is complex. During RRM, the viscosity is one of the key parameters and varies according to the polymer molecular weight due to chemical reactions. Simulation is a way to optimize this process. Prediction of the reactive flow is of great interest to optimize process conditions and wall thickness distribution of the molded part. We developed a solver based on smoothed particle hydrodynamics method. This Lagrangian meshfree method is well adapted to simulate free surface flows like those occurring in RRM. First, we validated the code comparing the simulation results to analytical Couette flow solution and experimental measurements of dam break problem. Then, we performed two-dimensional (2D) and 3D simulations to observe the influence of the change of viscosity on the flow, due to the chemical reactions. Adhesion of the polymer on the mold surface is modeled by new boundary conditions.Experimental and Numerical Analysis of the Flow Inside a Configuration Including an Axial Pump and a Tubular Exchanger
http://hdl.handle.net/10985/8586
Experimental and Numerical Analysis of the Flow Inside a Configuration Including an Axial Pump and a Tubular Exchanger
SOLIS, Moises; RAVELET, Florent; KHELLADI, Sofiane; BAKIR, Farid
In centrifugal and axial pumps, the flow is characterized by a turbulent and complex behavior and also by physical mechanisms such as cavitation and pressure fluctuations that are mainly due to the strong interactions between the fixed and mobile parts and the operating conditions. These fluctuations are more important at the tip clearance and propagate upstream and downstream of the rotor. The control of the fluctuating signal amplitudes can be achieved by incrementing the distance between the components mentioned above. This paper presents experimental and numerical results concerning the operation of a configuration that includes an axial pump and a bundle of tubes that mimics the cool source of a heat exchanger. The pump used in the tests has a low solidity and two blades designed in forced vortex, the tip clearance is approximately 3.87% of tip radius. The experimental measures were carried out using a test bench built for this purpose at the DynFluid Laboratory which was accomodated conveniently with a variety of instruments. Firstly, the characteristic curves were drawn for the pump at 1500 rpm and then a set of measurements concerning the use of pressure sensors was done in order to recover for different flow rates the static pressure signals upstream and downstream the pump and the exchanger. The pressure fluctuations and the performance curve were compared to the numerical results. The numerical simulations were carried out by using a Fluent code, the URANS (Unsteady Reynolds Averaged Navier-Stokes) approach and the k-ω SST turbulence model were applied to solve the unsteady, incompressible and turbulent flow. To record the fluctuating pressure signal, virtual sensors were necessary and placed at the same positions as in the experiments.
Fri, 01 Jan 2010 00:00:00 GMThttp://hdl.handle.net/10985/85862010-01-01T00:00:00ZSOLIS, MoisesRAVELET, FlorentKHELLADI, SofianeBAKIR, FaridIn centrifugal and axial pumps, the flow is characterized by a turbulent and complex behavior and also by physical mechanisms such as cavitation and pressure fluctuations that are mainly due to the strong interactions between the fixed and mobile parts and the operating conditions. These fluctuations are more important at the tip clearance and propagate upstream and downstream of the rotor. The control of the fluctuating signal amplitudes can be achieved by incrementing the distance between the components mentioned above. This paper presents experimental and numerical results concerning the operation of a configuration that includes an axial pump and a bundle of tubes that mimics the cool source of a heat exchanger. The pump used in the tests has a low solidity and two blades designed in forced vortex, the tip clearance is approximately 3.87% of tip radius. The experimental measures were carried out using a test bench built for this purpose at the DynFluid Laboratory which was accomodated conveniently with a variety of instruments. Firstly, the characteristic curves were drawn for the pump at 1500 rpm and then a set of measurements concerning the use of pressure sensors was done in order to recover for different flow rates the static pressure signals upstream and downstream the pump and the exchanger. The pressure fluctuations and the performance curve were compared to the numerical results. The numerical simulations were carried out by using a Fluent code, the URANS (Unsteady Reynolds Averaged Navier-Stokes) approach and the k-ω SST turbulence model were applied to solve the unsteady, incompressible and turbulent flow. To record the fluctuating pressure signal, virtual sensors were necessary and placed at the same positions as in the experiments.High Accuracy Volume Flow Rate Measurement Using Vortex Counting
http://hdl.handle.net/10985/8577
High Accuracy Volume Flow Rate Measurement Using Vortex Counting
ZAARAOUI, Abdelkader; RAVELET, Florent; MARGNAT, Florent; KHELLADI, Sofiane
A prototype device for measuring the volumetric flow-rate by counting vortices has been designed and realized. It consists of a square-section pipe in which are placed a two-dimensional bluff body and a strain gauge force sensor. These two elements are separated from each other, unlike the majority of vortex apparatus currently available. The principle is based on the generation of a separated wake behind the bluff body. The volumetric flow-rate measurement is done by counting vortices using a flat plate placed in the wake and attached to the beam sensor. By optimizing the geometrical arrangement, the search for a significant signal has shown that it was possible to get a quasi-periodic signal, within a good range of flow rates so that its performances are well deduced. The repeatability of the value of the volume of fluid passed for every vortex shed is tested for a given flow and then the accuracy of the measuring device is determined. This quantity is the constant of the device and is called the digital volume (V_p). It has the dimension of a volume and varies with the confinement of the flow and with the Reynolds number. Therefore, a dimensionless quantity is introduced, the reduced digital volume (V_r) that takes into account the average speed in the contracted section downstream of the bluff body. The reduced digital volume is found to be independent of the confinement in a significant range of Reynolds numbers, which gives the device a good accuracy.
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/10985/85772013-01-01T00:00:00ZZAARAOUI, AbdelkaderRAVELET, FlorentMARGNAT, FlorentKHELLADI, SofianeA prototype device for measuring the volumetric flow-rate by counting vortices has been designed and realized. It consists of a square-section pipe in which are placed a two-dimensional bluff body and a strain gauge force sensor. These two elements are separated from each other, unlike the majority of vortex apparatus currently available. The principle is based on the generation of a separated wake behind the bluff body. The volumetric flow-rate measurement is done by counting vortices using a flat plate placed in the wake and attached to the beam sensor. By optimizing the geometrical arrangement, the search for a significant signal has shown that it was possible to get a quasi-periodic signal, within a good range of flow rates so that its performances are well deduced. The repeatability of the value of the volume of fluid passed for every vortex shed is tested for a given flow and then the accuracy of the measuring device is determined. This quantity is the constant of the device and is called the digital volume (V_p). It has the dimension of a volume and varies with the confinement of the flow and with the Reynolds number. Therefore, a dimensionless quantity is introduced, the reduced digital volume (V_r) that takes into account the average speed in the contracted section downstream of the bluff body. The reduced digital volume is found to be independent of the confinement in a significant range of Reynolds numbers, which gives the device a good accuracy.Experimental study of hydraulic transport of large particles in horizontal pipes
http://hdl.handle.net/10985/8564
Experimental study of hydraulic transport of large particles in horizontal pipes
RAVELET, Florent; BAKIR, Farid; KHELLADI, Sofiane; REY, Robert
This article presents an experimental study of the hydraulic transport of very large solid particles (above 5 mm) in an horizontal pipe. Two specific masses are used for the solids. The solids are spheres that are large with respect to the diameter of the pipe (5, 10 and 15%) or real stones of arbitrary shapes but constant specific mass and a size distribution similar to the tested spherical beads. Finally, mixtures of size and / or specific mass are studied. The regimes are characterized with differential pressure measurements and visualizations. The results are compared to empirical models based on dimensionless numbers, together with 1D models that are based on mass and momentum balance. A model for the transport of large particles in vertical pipes is also proposed and tested on data available in the Literature, in order to compare the trends that are observed in the present experiments in a horizontal pipe to the trends predicted for a vertical pipe. The results show that the grain size and specific mass have a strong effect on the transition point between regimes with a stationary bed and dispersed flows. The pressure drops are moreover smaller for large particles in the horizontal part contrary to what occurs for vertical pipes, and to the predictions of the empirical correlations.
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/10985/85642013-01-01T00:00:00ZRAVELET, FlorentBAKIR, FaridKHELLADI, SofianeREY, RobertThis article presents an experimental study of the hydraulic transport of very large solid particles (above 5 mm) in an horizontal pipe. Two specific masses are used for the solids. The solids are spheres that are large with respect to the diameter of the pipe (5, 10 and 15%) or real stones of arbitrary shapes but constant specific mass and a size distribution similar to the tested spherical beads. Finally, mixtures of size and / or specific mass are studied. The regimes are characterized with differential pressure measurements and visualizations. The results are compared to empirical models based on dimensionless numbers, together with 1D models that are based on mass and momentum balance. A model for the transport of large particles in vertical pipes is also proposed and tested on data available in the Literature, in order to compare the trends that are observed in the present experiments in a horizontal pipe to the trends predicted for a vertical pipe. The results show that the grain size and specific mass have a strong effect on the transition point between regimes with a stationary bed and dispersed flows. The pressure drops are moreover smaller for large particles in the horizontal part contrary to what occurs for vertical pipes, and to the predictions of the empirical correlations.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.3D Model for Powder Compact Densification in Rotational Molding
http://hdl.handle.net/10985/9894
3D Model for Powder Compact Densification in Rotational Molding
ASGARPOUR, Monir; BAKIR, Farid; KHELLADI, Sofiane; KHAVANDI, Alireza; TCHARKHTCHI, Abbas
During rotational molding, a loosely packed, low-density powder compact transforms into a fully densified polymer part. This transformation is a consequence of particles sintering. Powder compact density evolution of the polymer powder is measured experimentally. Obtained results show that the powder densification process consists of two stages, and its mechanism during these two stages is not the same. During the first stage, densification occurs by grains coalescence, and air between the grains escape by open pores between particles. These open pores close in time by particles coalescence progress, and remaining air entrapped in polymer melt becomes air bubbles. Surface tension, viscosity, grains size, and temperature are the controlling parameters during first stage. A three-dimensional model is proposed for the densification of polymer powder during first stage. Second stage starts after bubble forming. Diffusion is the controlling phenomena during this stage. A diffusion-based model is used for the second stage of densification. By comparing with the other models, proposed model exhibits several advantages: it is proposed in three-dimensional and takes into account the nature of layer-by-layer powder densification. Model verification by experimental data obtained for densification of two different polymers shows a close agreement between model prediction and experiments.
Sun, 01 Jan 2012 00:00:00 GMThttp://hdl.handle.net/10985/98942012-01-01T00:00:00ZASGARPOUR, MonirBAKIR, FaridKHELLADI, SofianeKHAVANDI, AlirezaTCHARKHTCHI, AbbasDuring rotational molding, a loosely packed, low-density powder compact transforms into a fully densified polymer part. This transformation is a consequence of particles sintering. Powder compact density evolution of the polymer powder is measured experimentally. Obtained results show that the powder densification process consists of two stages, and its mechanism during these two stages is not the same. During the first stage, densification occurs by grains coalescence, and air between the grains escape by open pores between particles. These open pores close in time by particles coalescence progress, and remaining air entrapped in polymer melt becomes air bubbles. Surface tension, viscosity, grains size, and temperature are the controlling parameters during first stage. A three-dimensional model is proposed for the densification of polymer powder during first stage. Second stage starts after bubble forming. Diffusion is the controlling phenomena during this stage. A diffusion-based model is used for the second stage of densification. By comparing with the other models, proposed model exhibits several advantages: it is proposed in three-dimensional and takes into account the nature of layer-by-layer powder densification. Model verification by experimental data obtained for densification of two different polymers shows a close agreement between model prediction and experiments.New high-resolution-preserving sliding mesh techniques for higher-order finite volume schemes
http://hdl.handle.net/10985/17818
New high-resolution-preserving sliding mesh techniques for higher-order finite volume schemes
RAMÍREZ, Luis; FOULQUIÉ, Charles; NOGUEIRA, Xesús; KHELLADI, Sofiane; CHASSAING, Jean-Camille; COLOMINAS, Ignasi
This paper presents a new sliding mesh technique for the computation of unsteady viscous flows in the presence of rotating bodies. The compressible Euler and incompressible Navier–Stokes equations are solved using a higher-order (>2) finite volume method on unstructured grids. A sliding mesh approach is employed at the interface between computational grids in relative motion. In order to prevent loss of accuracy, two distinct families of higher-order sliding mesh interfaces are developed. These approaches fit naturally in a high-order finite volume framework. To this end, Moving Least Squares (MLS) approximants are used for the transmission of the information from one grid to another. A particular attention is paid for the study of the accuracy and conservation properties of the numerical scheme for static and rotating grids. The capabilities of the present solver to compute complex unsteady vortical flow motions created by rotating geometries are illustrated on a cross-flow configuration.
Thu, 01 Jan 2015 00:00:00 GMThttp://hdl.handle.net/10985/178182015-01-01T00:00:00ZRAMÍREZ, LuisFOULQUIÉ, CharlesNOGUEIRA, XesúsKHELLADI, SofianeCHASSAING, Jean-CamilleCOLOMINAS, IgnasiThis paper presents a new sliding mesh technique for the computation of unsteady viscous flows in the presence of rotating bodies. The compressible Euler and incompressible Navier–Stokes equations are solved using a higher-order (>2) finite volume method on unstructured grids. A sliding mesh approach is employed at the interface between computational grids in relative motion. In order to prevent loss of accuracy, two distinct families of higher-order sliding mesh interfaces are developed. These approaches fit naturally in a high-order finite volume framework. To this end, Moving Least Squares (MLS) approximants are used for the transmission of the information from one grid to another. A particular attention is paid for the study of the accuracy and conservation properties of the numerical scheme for static and rotating grids. The capabilities of the present solver to compute complex unsteady vortical flow motions created by rotating geometries are illustrated on a cross-flow configuration.