The Experts below are selected from a list of 3618 Experts worldwide ranked by ideXlab platform
Zhaolong Han - One of the best experts on this subject based on the ideXlab platform.
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aerodynamic noise assessment for a vertical axis wind turbine using improved delayed Detached Eddy Simulation
Renewable Energy, 2019Co-Authors: Hang Lei, Dai Zhou, Yan Bao, Zhaolong Han, Hongbo Zhu, Lei ZhouAbstract:Abstract This paper presents the results of the aerodynamic and aeroacoustic assessment for a vertical axis wind turbine (VAWT). The Improved Delayed Detached Eddy Simulation (IDDES) technique and Ffowcs Williams and Hawkings (FW-H) acoustic analogy method are adopted to simulate instantaneous flow field and to perform the noise prediction in the far field. The CFD model is verified against available experimental data for the power coefficient. The acoustic pressure spectra of thickness, loading, and quadrupole noise are presented, and the mechanisms and contributions of different noise are discussed. The effects of increasing rotational speed, receiver distance and turbulence intensity are studied. The results indicate that the thickness and loading noises are the dominant noise sources, while the influence of quadrupole noise is not negligible when the Mach number increases. Higher tip speed ratio and increased loads on blades will generate larger thickness and loading noise. In addition to the changes in lift and drag forces, higher turbulence intensity will make stronger interaction between vortex structures and blades, thereby induces a higher level of noise. It is concluded that this work could be exploited to design quieter vertical axis wind turbines and to locate the wind turbine position that minimizes noise pollution.
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three dimensional improved delayed Detached Eddy Simulation of a two bladed vertical axis wind turbine
Energy Conversion and Management, 2017Co-Authors: Hang Lei, Dai Zhou, Yan Bao, Zhaolong HanAbstract:Abstract The aerodynamic performance of a two-bladed vertical axis wind turbine is investigated using the turbulence model of the Improved Delayed Detached Eddy Simulation and the polyhedral mesh. The sliding mesh technique is used to simulate the rotation of the rotor. Meanwhile, the results obtained by the shear stress transport k-ω model are presented as contrast. Then, the simulated power coefficients at different tip speed ratios and the wake velocity are validated by comparison with the experimental data from available literature. It is shown that the power coefficients and wake velocity predicted by the Improved Delayed Detached Eddy Simulation are closer to the experimental data than those by the shear stress transport k-ω model. The pressure distributions predicted by the two turbulence models show different degrees of discrepancies in different scales of flow separation. By comparing the vorticity magnitude graphs, the Improved Delayed Detached Eddy Simulation is found to be able to capture more exquisite vortices after the flow separations. Limited by its inherent ability, the shear stress transport k-ω model predicts vortices that are less realistic than those of Improved Delayed Detached Eddy Simulation. Hence, it may cause some errors in predicting the pressure distributions, especially when the blades suffer dynamic stall. It is demonstrated that the Improved Delayed Detached Eddy Simulation is regarded as a reliable model to analyze the aerodynamic performance of vertical axis wine turbines.
Sebastien Deck - One of the best experts on this subject based on the ideXlab platform.
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zonal Detached Eddy Simulation applied to the tip clearance flow in an axial compressor
AIAA Journal, 2016Co-Authors: William Riera, Julien Marty, L Castillon, Sebastien DeckAbstract:This paper presents the study of the tip-clearance flow in an axial compressor using several turbulence-modeling approaches: Reynolds-averaged Navier–Stokes, unsteady Reynolds-averaged Navier–Stokes, and zonal Detached-Eddy Simulation. Rotor Simulations are carried out on the same mesh based on the zonal-Detached-Eddy-Simulation requirements, and compared to experimental data. Zonal Detached-Eddy Simulation brings significant improvements over Reynolds-averaged Navier–Stokes and unsteady Reynolds-averaged Navier–Stokes approaches to reach accurate integral values, especially the total-pressure-gradient prediction near the casing, as well as to capture complex flow patterns near the casing. Whereas the unsteady Reynolds-averaged Navier–Stokes method predicts only tip-leakage and induced vortices, the zonal-Detached-Eddy-Simulation approach is able to reveal more complex phenomena as the tip-leakage vortex, the contra-rotative induced vortex, and numerous secondary vortices are captured. Because of their in...
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zonal Detached Eddy Simulation of the flow around a simplified launcher afterbody
AIAA Journal, 2014Co-Authors: R Pain, Pierreelie Weiss, Sebastien DeckAbstract:This paper presents the numerical investigation of the unsteady separated flow around a simplified space-launcher afterbody. A zonal Detached Eddy Simulation is used to deal with the high-Reynolds-number flow. The geometry consists of a cylinder of finite length extended by another cylinder of smaller diameter for the central body, and two cylinders similar to the Ariane 5 launcher boosters on each side. The main purpose was to evidence the impact of the side cylinders on the flow characteristics of the isolated central body. To this end, instantaneous and statistical results are compared to those of the isolated central body. The flow topology with side cylinders is found to be dramatically different from that of the axisymmetric case. The mean and rms values for the pressure and velocity fields appear to be organized along the two planes of symmetry of the geometry. Besides, the levels of the mean wall-pressure coefficients are lower by 10% in the three-body configuration. Conversely, the maximum rms co...
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Zonal Detached Eddy Simulation (ZDES) of a spatially developing flat plate turbulent boundary layer over the Reynolds number range 3 150 ⩽ Reθ ⩽ 14 000
Physics of Fluids, 2014Co-Authors: Sebastien Deck, Nicolas Renard, Romain Laraufie, Pierre SagautAbstract:A Wall-Modeled Large Eddy Simulation (WMLES) of a spatially developing zero-pressure gradient smooth flat plate turbulent boundary layer is performed by means of the third mode of the Zonal Detached Eddy Simulation technique. The outer layer is resolved by a Large Eddy Simulation whereas the wall is modeled by a RANS Simulation zone, with a RANS/LES interface prescribed at a fixed location. A revisited cost assessment of the Direct Numerical Simulation of high Reynolds numbers (Reθ ⩾ 10 000) wall-bounded flows emphasizes how moderate the cost of the WMLES approach is compared to methods resolving the near-wall dynamics. This makes possible the Simulation over a wide Reynolds number range 3 150 ⩽ Reθ ⩽ 14 000, leaving quite enough space for very large scale motions to develop. For a better skin friction prediction, it is shown that the RANS/LES interface should be high enough in the boundary layer and at a location scaling in boundary layer thickness units (e.g., 0.1δ) rather than in wall units. Velocity s...
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Recent improvements in the Zonal Detached Eddy Simulation (ZDES) formulation
Theoretical and Computational Fluid Dynamics, 2012Co-Authors: Sebastien DeckAbstract:An efficient generalized Zonal Detached Eddy Simulation method (ZDES) is presented, which aims at performing hybrid Reynolds Averaged Numerical Simulation (RANS)/Large Eddy Simulation (LES) calculations for both internal and external aerodynamics problems. It is based on a zonal formulation of the hybrid length scale that allows to combine the zonal approach with the best features of Delayed Detached Eddy Simulation (DDES) (Spalart et al. Theor Comput Fluid Dyn 20:181–195, 2006 ). In other words, the presumed weak point of a zonal approach, namely that the location of separation has to be known in advance, is now overcome. What is more, the problem of slow LES content development in mixing layers when they are treated neither in RANS nor in LES mode is investigated. It is argued that the subgrid length scale Δ_max = max(Δ x , Δ y , Δ z ) entering DDES is physically justified to shield the boundary layer but is definitely not a good subgrid length scale in LES mode. Remedies are proposed based on new zonal subgrid length scales that depend not only on the grid spacing but also on the flow solution and especially on the local vorticity vector. The method is validated on a spatially developing mixing layer as well as in a backward facing step flow and then applied to a three-element airfoil. It is argued in this latter case that a precise control of the RANS mode thanks to a zonal approach is essential. More generally, in all simulated cases in this study, ZDES has proven to be very efficient as regards the behavior in LES mode while retaining the strongest asset of DDES, namely the treatment of the attached boundary layer in RANS mode. The issue of zonal or non-zonal treatment of turbulent flows is also briefly discussed.
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zonal Detached Eddy Simulation of a spatially developing flat plate turbulent boundary layer
Computers & Fluids, 2011Co-Authors: Sebastien Deck, Pierreelie Weiss, Mathieu Pamies, Eric GarnierAbstract:Abstract The present work presents a Zonal Detached Eddy Simulation (ZDES) to simulate a spatially developing turbulent boundary layer over a smooth flat plate at Reθ = 2900. Results are compared with the experimental data of De Graaff and Eaton [1] . A synthetic reconstruction method for the pseudo-viscosity field ν ˜ is proposed in the frame of a synthetic Eddy method. First, it is shown that ZDES amounts to LES with a plausible one-equation subgrid scale model and wall modeling. More precisely, both the mean and second-order field are well predicted compared with the experiment and a reference LES with the mixed-scale-model. The separate effect of the streamwise (respectively spanwise) resolution on skin friction and turbulence is then evaluated. A measure of the global error which is based on the error on the friction and on the turbulent shear stresses has been defined. It is observed that without fixing the height of the RANS-LES interface, the error does not vary monotonicaly with the resolution. Conversely, fixing the interface height to 50 or 100 wall unit brings both an intuitive reduction of the error with the resolution and a global reduction of the error level with respect to the aforementioned case. Furthermore, it is outlined in this study of spatially developing boundary layer that the potential computational effort reduction brought by RANS-LES approaches depends not only on the grid resolution but also on the establishment distance of the solution.
Hang Lei - One of the best experts on this subject based on the ideXlab platform.
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aerodynamic noise assessment for a vertical axis wind turbine using improved delayed Detached Eddy Simulation
Renewable Energy, 2019Co-Authors: Hang Lei, Dai Zhou, Yan Bao, Zhaolong Han, Hongbo Zhu, Lei ZhouAbstract:Abstract This paper presents the results of the aerodynamic and aeroacoustic assessment for a vertical axis wind turbine (VAWT). The Improved Delayed Detached Eddy Simulation (IDDES) technique and Ffowcs Williams and Hawkings (FW-H) acoustic analogy method are adopted to simulate instantaneous flow field and to perform the noise prediction in the far field. The CFD model is verified against available experimental data for the power coefficient. The acoustic pressure spectra of thickness, loading, and quadrupole noise are presented, and the mechanisms and contributions of different noise are discussed. The effects of increasing rotational speed, receiver distance and turbulence intensity are studied. The results indicate that the thickness and loading noises are the dominant noise sources, while the influence of quadrupole noise is not negligible when the Mach number increases. Higher tip speed ratio and increased loads on blades will generate larger thickness and loading noise. In addition to the changes in lift and drag forces, higher turbulence intensity will make stronger interaction between vortex structures and blades, thereby induces a higher level of noise. It is concluded that this work could be exploited to design quieter vertical axis wind turbines and to locate the wind turbine position that minimizes noise pollution.
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three dimensional improved delayed Detached Eddy Simulation of a two bladed vertical axis wind turbine
Energy Conversion and Management, 2017Co-Authors: Hang Lei, Dai Zhou, Yan Bao, Zhaolong HanAbstract:Abstract The aerodynamic performance of a two-bladed vertical axis wind turbine is investigated using the turbulence model of the Improved Delayed Detached Eddy Simulation and the polyhedral mesh. The sliding mesh technique is used to simulate the rotation of the rotor. Meanwhile, the results obtained by the shear stress transport k-ω model are presented as contrast. Then, the simulated power coefficients at different tip speed ratios and the wake velocity are validated by comparison with the experimental data from available literature. It is shown that the power coefficients and wake velocity predicted by the Improved Delayed Detached Eddy Simulation are closer to the experimental data than those by the shear stress transport k-ω model. The pressure distributions predicted by the two turbulence models show different degrees of discrepancies in different scales of flow separation. By comparing the vorticity magnitude graphs, the Improved Delayed Detached Eddy Simulation is found to be able to capture more exquisite vortices after the flow separations. Limited by its inherent ability, the shear stress transport k-ω model predicts vortices that are less realistic than those of Improved Delayed Detached Eddy Simulation. Hence, it may cause some errors in predicting the pressure distributions, especially when the blades suffer dynamic stall. It is demonstrated that the Improved Delayed Detached Eddy Simulation is regarded as a reliable model to analyze the aerodynamic performance of vertical axis wine turbines.
Dai Zhou - One of the best experts on this subject based on the ideXlab platform.
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aerodynamic noise assessment for a vertical axis wind turbine using improved delayed Detached Eddy Simulation
Renewable Energy, 2019Co-Authors: Hang Lei, Dai Zhou, Yan Bao, Zhaolong Han, Hongbo Zhu, Lei ZhouAbstract:Abstract This paper presents the results of the aerodynamic and aeroacoustic assessment for a vertical axis wind turbine (VAWT). The Improved Delayed Detached Eddy Simulation (IDDES) technique and Ffowcs Williams and Hawkings (FW-H) acoustic analogy method are adopted to simulate instantaneous flow field and to perform the noise prediction in the far field. The CFD model is verified against available experimental data for the power coefficient. The acoustic pressure spectra of thickness, loading, and quadrupole noise are presented, and the mechanisms and contributions of different noise are discussed. The effects of increasing rotational speed, receiver distance and turbulence intensity are studied. The results indicate that the thickness and loading noises are the dominant noise sources, while the influence of quadrupole noise is not negligible when the Mach number increases. Higher tip speed ratio and increased loads on blades will generate larger thickness and loading noise. In addition to the changes in lift and drag forces, higher turbulence intensity will make stronger interaction between vortex structures and blades, thereby induces a higher level of noise. It is concluded that this work could be exploited to design quieter vertical axis wind turbines and to locate the wind turbine position that minimizes noise pollution.
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three dimensional improved delayed Detached Eddy Simulation of a two bladed vertical axis wind turbine
Energy Conversion and Management, 2017Co-Authors: Hang Lei, Dai Zhou, Yan Bao, Zhaolong HanAbstract:Abstract The aerodynamic performance of a two-bladed vertical axis wind turbine is investigated using the turbulence model of the Improved Delayed Detached Eddy Simulation and the polyhedral mesh. The sliding mesh technique is used to simulate the rotation of the rotor. Meanwhile, the results obtained by the shear stress transport k-ω model are presented as contrast. Then, the simulated power coefficients at different tip speed ratios and the wake velocity are validated by comparison with the experimental data from available literature. It is shown that the power coefficients and wake velocity predicted by the Improved Delayed Detached Eddy Simulation are closer to the experimental data than those by the shear stress transport k-ω model. The pressure distributions predicted by the two turbulence models show different degrees of discrepancies in different scales of flow separation. By comparing the vorticity magnitude graphs, the Improved Delayed Detached Eddy Simulation is found to be able to capture more exquisite vortices after the flow separations. Limited by its inherent ability, the shear stress transport k-ω model predicts vortices that are less realistic than those of Improved Delayed Detached Eddy Simulation. Hence, it may cause some errors in predicting the pressure distributions, especially when the blades suffer dynamic stall. It is demonstrated that the Improved Delayed Detached Eddy Simulation is regarded as a reliable model to analyze the aerodynamic performance of vertical axis wine turbines.
Yan Bao - One of the best experts on this subject based on the ideXlab platform.
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aerodynamic noise assessment for a vertical axis wind turbine using improved delayed Detached Eddy Simulation
Renewable Energy, 2019Co-Authors: Hang Lei, Dai Zhou, Yan Bao, Zhaolong Han, Hongbo Zhu, Lei ZhouAbstract:Abstract This paper presents the results of the aerodynamic and aeroacoustic assessment for a vertical axis wind turbine (VAWT). The Improved Delayed Detached Eddy Simulation (IDDES) technique and Ffowcs Williams and Hawkings (FW-H) acoustic analogy method are adopted to simulate instantaneous flow field and to perform the noise prediction in the far field. The CFD model is verified against available experimental data for the power coefficient. The acoustic pressure spectra of thickness, loading, and quadrupole noise are presented, and the mechanisms and contributions of different noise are discussed. The effects of increasing rotational speed, receiver distance and turbulence intensity are studied. The results indicate that the thickness and loading noises are the dominant noise sources, while the influence of quadrupole noise is not negligible when the Mach number increases. Higher tip speed ratio and increased loads on blades will generate larger thickness and loading noise. In addition to the changes in lift and drag forces, higher turbulence intensity will make stronger interaction between vortex structures and blades, thereby induces a higher level of noise. It is concluded that this work could be exploited to design quieter vertical axis wind turbines and to locate the wind turbine position that minimizes noise pollution.
-
three dimensional improved delayed Detached Eddy Simulation of a two bladed vertical axis wind turbine
Energy Conversion and Management, 2017Co-Authors: Hang Lei, Dai Zhou, Yan Bao, Zhaolong HanAbstract:Abstract The aerodynamic performance of a two-bladed vertical axis wind turbine is investigated using the turbulence model of the Improved Delayed Detached Eddy Simulation and the polyhedral mesh. The sliding mesh technique is used to simulate the rotation of the rotor. Meanwhile, the results obtained by the shear stress transport k-ω model are presented as contrast. Then, the simulated power coefficients at different tip speed ratios and the wake velocity are validated by comparison with the experimental data from available literature. It is shown that the power coefficients and wake velocity predicted by the Improved Delayed Detached Eddy Simulation are closer to the experimental data than those by the shear stress transport k-ω model. The pressure distributions predicted by the two turbulence models show different degrees of discrepancies in different scales of flow separation. By comparing the vorticity magnitude graphs, the Improved Delayed Detached Eddy Simulation is found to be able to capture more exquisite vortices after the flow separations. Limited by its inherent ability, the shear stress transport k-ω model predicts vortices that are less realistic than those of Improved Delayed Detached Eddy Simulation. Hence, it may cause some errors in predicting the pressure distributions, especially when the blades suffer dynamic stall. It is demonstrated that the Improved Delayed Detached Eddy Simulation is regarded as a reliable model to analyze the aerodynamic performance of vertical axis wine turbines.