It is highly attractive to develop an efficient and flexible large eddy simulation(LES)technique for high-Reynolds-number atmospheric boundary layer(ABL)simulation using the low-order numerical scheme on a relatively ...It is highly attractive to develop an efficient and flexible large eddy simulation(LES)technique for high-Reynolds-number atmospheric boundary layer(ABL)simulation using the low-order numerical scheme on a relatively coarse grid,that could reproduce the logarithmic profile of the mean velocity and some key features of large-scale coherent structures in the outer layer.In this study,an improved near-wall correction scheme for the vertical gradient of the resolved streamwise velocity in the strain-rate tensor is proposed to calculate the eddy viscosity coefficient in the subgrid-scale(SGS)model.The LES code is realized with a second-order finite-difference scheme,the scale-dependent dynamic SGS stress model,the equilibrium wall stress model,and the proposed correction scheme.Very-high-Reynolds-number ABL flow simulation under the neutral stratification condition is conducted to assess the performance of the method in predicting the mean and fluctuating characteristics of the rough-wall turbulence.It is found that the logarithmic profile of the mean streamwise velocity and some key features of large-scale coherent structures can be reasonably predicted by adopting the proposed correction method and the low-order numerical scheme.展开更多
This article deals with real-time hi-fi simulation of large aircraft flying in turbulent wind in a simulator to study its takeoff and landing behavior in microburst wind shear. A parameterized three-dimensional （3D）...This article deals with real-time hi-fi simulation of large aircraft flying in turbulent wind in a simulator to study its takeoff and landing behavior in microburst wind shear. A parameterized three-dimensional （3D） microburst model is built up on the basis of vortex ring and Rankine vortex principle. Complicated microburst wind fields are simulated by means of vortex ring declination and multi-vortex superposition. Based on the modeling data of Boeing 747-100, a dynamic model with wind shear effects considered is established and a general method to modify the aerodynamic model is proposed. A controller for longitudinal and lateral escapes is designed and verified in simulated microburst wind field. Results indicate that, with high extensibility, reasonability and effectiveness, the 3D microburst model with wind shear effects considered is fit to simulate real wind fields. Different escape schemes can be adopted to fly through a wind field from different locations. The model can be used for real-time flight simulation in a flight simulator.展开更多
In order to understand the physical phenomenon of the reflected shock/turbulent boundary layer interaction,the Large Eddy Simulation(LES)is conducted to investigate shock wave and turbulent boundary layer interaction ...In order to understand the physical phenomenon of the reflected shock/turbulent boundary layer interaction,the Large Eddy Simulation(LES)is conducted to investigate shock wave and turbulent boundary layer interaction in a 12°compression ramp with inlet high Mach number of 2.9.Rescaling/recycling method is used as inflow turbulence generation technique and validated on a supersonic flat plate turbulent boundary layer.The flow field of recycling plane in the plate computation domain is obtained to give the inlet boundary condition for the LES computation.This paper focuses on the reflected shock/turbulent boundary layer interaction region,where the fine flow structure and instantaneous flow field are analyzed in detail.It is found that the unsteady motion of the shock wave leads to the increase of wall pressure fluctuation.展开更多
With the method of large-eddy simulation,the equation of spherule motion and the method of immersed boundary condition,numerical simulations of three-dimen-sional turbulent aeolian motion and the formation of sand rip...With the method of large-eddy simulation,the equation of spherule motion and the method of immersed boundary condition,numerical simulations of three-dimen-sional turbulent aeolian motion and the formation of sand ripples under three-di-mensional turbulent wind and the mutual actions of saltation and creeping motion were carried out. The resulting sand ripples have the form that is flat on the upwind side and steep on the leeward,which is identical to the sand ripples in nature. We also realized the self-restoration process of three-dimensional sand ripples,which shows the correctness of the method of numerical simulation and the models of saltation and creeping. Finally,We analyzed the influence of sand ripples on the three-dimensional turbulent wind field,and found that due to the appearance and development of sand ripples,in the normal direction of ground there exists stronger energy exchange,and moreover,there is close correspondence between the forms of sand ripples and the vorticity close to the ground surface.展开更多
To investigate the transient transport and entrapment of argon bubbles and inclusions simultaneously during continuous casting,a 3D large eddy simulation model coupling molten steel flow,solidification and particle mo...To investigate the transient transport and entrapment of argon bubbles and inclusions simultaneously during continuous casting,a 3D large eddy simulation model coupling molten steel flow,solidification and particle motion was constructed.In this model,momentum transfer between molten steel and argon bubbles was performed by two-way coupling.The predicted results indicate that argon bubble injection changed the flow pattern of molten steel and the inclusion motion in the liquid pool.Consequently,the inclusion capture near the solidifying front was changed.In addition,measurements of bubbles and inclusions in the obtained samples were performed by methods of optical microscope examination and galvanostatic electrolysis.The results show a favorable agreement between the model predictions and the measured results,which validate the mathematical model.Furthermore,the predicted results of the inclusion entrapment in the case with argon bubble injection are more compatible with the measurements than those in the case without argon bubble injection.展开更多
采用自行开发的大涡模拟(Large-Eddy Simulation,LES)和离散单元法(Discrete Element Method,DEM)耦合的数值计算程序,对风沙气固两相三维运动进行了数值模拟。对近床面沙粒的起跳速度、起跳角、入射速度和入射角的概率分布,以及沙粒展...采用自行开发的大涡模拟(Large-Eddy Simulation,LES)和离散单元法(Discrete Element Method,DEM)耦合的数值计算程序,对风沙气固两相三维运动进行了数值模拟。对近床面沙粒的起跳速度、起跳角、入射速度和入射角的概率分布,以及沙粒展向速度的分布做出统计分析。结果显示:本文所建立两相耦合数值模型,能够复现风沙输移中散体沙粒的运动特征;入射速度和起跳速度服从对数正态分布,并随着来流平均风速增大,概率分布呈现集中趋势;入射角、起跳角分别集中在10°和15°左右,表明沙粒动能向垂直方向转移的趋势;沙粒的展向速度的随来流风速增大而更加显著。展开更多
高雷诺数壁湍流(high Reynolds number wall-bounded turbulence,HRNWT)是目前湍流科学研究的一个热点也是一个难点,对其现象、规律及机制的认知不足,理论体系远未建立而且研究手段受到各种限制.本文基于对HRNWT主要研究手段的介绍,针对...高雷诺数壁湍流(high Reynolds number wall-bounded turbulence,HRNWT)是目前湍流科学研究的一个热点也是一个难点,对其现象、规律及机制的认知不足,理论体系远未建立而且研究手段受到各种限制.本文基于对HRNWT主要研究手段的介绍,针对HRNWT中的湍流统计量、超大尺度结构(very large scale motions,VLSMs)的尺度和形态以及起源和影响及其与颗粒的相互作用,总结了HRNWT的研究现状和最新进展,特别梳理了近年来本文作者团队在HRNWT特别是高雷诺数颗粒两相壁湍流方面的研究成果,并对HRNWT的进一步研究给出了建议及展望.展开更多
基金Project supported by the National Natural Science Foundation of China(No.11490551)the Fundamental Research Funds for the Central Universities(Nos.lzujbky-2016-k13 and lzujbky-2018-k07)
文摘It is highly attractive to develop an efficient and flexible large eddy simulation(LES)technique for high-Reynolds-number atmospheric boundary layer(ABL)simulation using the low-order numerical scheme on a relatively coarse grid,that could reproduce the logarithmic profile of the mean velocity and some key features of large-scale coherent structures in the outer layer.In this study,an improved near-wall correction scheme for the vertical gradient of the resolved streamwise velocity in the strain-rate tensor is proposed to calculate the eddy viscosity coefficient in the subgrid-scale(SGS)model.The LES code is realized with a second-order finite-difference scheme,the scale-dependent dynamic SGS stress model,the equilibrium wall stress model,and the proposed correction scheme.Very-high-Reynolds-number ABL flow simulation under the neutral stratification condition is conducted to assess the performance of the method in predicting the mean and fluctuating characteristics of the rough-wall turbulence.It is found that the logarithmic profile of the mean streamwise velocity and some key features of large-scale coherent structures can be reasonably predicted by adopting the proposed correction method and the low-order numerical scheme.
基金Foundation item： Program of National Natural Science Foundation of China and The Civil Aviation （60776812）
文摘This article deals with real-time hi-fi simulation of large aircraft flying in turbulent wind in a simulator to study its takeoff and landing behavior in microburst wind shear. A parameterized three-dimensional （3D） microburst model is built up on the basis of vortex ring and Rankine vortex principle. Complicated microburst wind fields are simulated by means of vortex ring declination and multi-vortex superposition. Based on the modeling data of Boeing 747-100, a dynamic model with wind shear effects considered is established and a general method to modify the aerodynamic model is proposed. A controller for longitudinal and lateral escapes is designed and verified in simulated microburst wind field. Results indicate that, with high extensibility, reasonability and effectiveness, the 3D microburst model with wind shear effects considered is fit to simulate real wind fields. Different escape schemes can be adopted to fly through a wind field from different locations. The model can be used for real-time flight simulation in a flight simulator.
基金co-supported by the National Key Project GJXM92579 of Chinathe National Natural Science Foundation of China(No.11532007)。
文摘In order to understand the physical phenomenon of the reflected shock/turbulent boundary layer interaction,the Large Eddy Simulation(LES)is conducted to investigate shock wave and turbulent boundary layer interaction in a 12°compression ramp with inlet high Mach number of 2.9.Rescaling/recycling method is used as inflow turbulence generation technique and validated on a supersonic flat plate turbulent boundary layer.The flow field of recycling plane in the plate computation domain is obtained to give the inlet boundary condition for the LES computation.This paper focuses on the reflected shock/turbulent boundary layer interaction region,where the fine flow structure and instantaneous flow field are analyzed in detail.It is found that the unsteady motion of the shock wave leads to the increase of wall pressure fluctuation.
基金the Key Project of National Natural Science Foundation of China (Grant No. 10532040)
文摘With the method of large-eddy simulation,the equation of spherule motion and the method of immersed boundary condition,numerical simulations of three-dimen-sional turbulent aeolian motion and the formation of sand ripples under three-di-mensional turbulent wind and the mutual actions of saltation and creeping motion were carried out. The resulting sand ripples have the form that is flat on the upwind side and steep on the leeward,which is identical to the sand ripples in nature. We also realized the self-restoration process of three-dimensional sand ripples,which shows the correctness of the method of numerical simulation and the models of saltation and creeping. Finally,We analyzed the influence of sand ripples on the three-dimensional turbulent wind field,and found that due to the appearance and development of sand ripples,in the normal direction of ground there exists stronger energy exchange,and moreover,there is close correspondence between the forms of sand ripples and the vorticity close to the ground surface.
基金The authors gratefully express their appreciation to the National Natural Science Foundation of China(51834002)Fundamental Research Funds for the Central Universities(FRF-AT-20-05)for sponsoring this work.
文摘To investigate the transient transport and entrapment of argon bubbles and inclusions simultaneously during continuous casting,a 3D large eddy simulation model coupling molten steel flow,solidification and particle motion was constructed.In this model,momentum transfer between molten steel and argon bubbles was performed by two-way coupling.The predicted results indicate that argon bubble injection changed the flow pattern of molten steel and the inclusion motion in the liquid pool.Consequently,the inclusion capture near the solidifying front was changed.In addition,measurements of bubbles and inclusions in the obtained samples were performed by methods of optical microscope examination and galvanostatic electrolysis.The results show a favorable agreement between the model predictions and the measured results,which validate the mathematical model.Furthermore,the predicted results of the inclusion entrapment in the case with argon bubble injection are more compatible with the measurements than those in the case without argon bubble injection.
文摘采用自行开发的大涡模拟(Large-Eddy Simulation,LES)和离散单元法(Discrete Element Method,DEM)耦合的数值计算程序,对风沙气固两相三维运动进行了数值模拟。对近床面沙粒的起跳速度、起跳角、入射速度和入射角的概率分布,以及沙粒展向速度的分布做出统计分析。结果显示:本文所建立两相耦合数值模型,能够复现风沙输移中散体沙粒的运动特征;入射速度和起跳速度服从对数正态分布,并随着来流平均风速增大,概率分布呈现集中趋势;入射角、起跳角分别集中在10°和15°左右,表明沙粒动能向垂直方向转移的趋势;沙粒的展向速度的随来流风速增大而更加显著。
文摘高雷诺数壁湍流(high Reynolds number wall-bounded turbulence,HRNWT)是目前湍流科学研究的一个热点也是一个难点,对其现象、规律及机制的认知不足,理论体系远未建立而且研究手段受到各种限制.本文基于对HRNWT主要研究手段的介绍,针对HRNWT中的湍流统计量、超大尺度结构(very large scale motions,VLSMs)的尺度和形态以及起源和影响及其与颗粒的相互作用,总结了HRNWT的研究现状和最新进展,特别梳理了近年来本文作者团队在HRNWT特别是高雷诺数颗粒两相壁湍流方面的研究成果,并对HRNWT的进一步研究给出了建议及展望.
