The flow around an axisymmetric body of revolution(DARPA SUBOFF bare model)at Re=1.2×10^(7)is numerically investigated using the wall-modeled large eddy simulation(WMLES).To evaluate the capabilities of WMLES in ...The flow around an axisymmetric body of revolution(DARPA SUBOFF bare model)at Re=1.2×10^(7)is numerically investigated using the wall-modeled large eddy simulation(WMLES).To evaluate the capabilities of WMLES in such wall-bounded turbulent flows,the effects of the wall stress model and sampling distance are systematically studied.The numerical results of the non-equilibrium wall stress model with an appropriate sampling distance are in good agreement with the experiments in terms of pressure coefficient,skin-friction coefficient,and drag coefficient.On this basis,the thickening of the turbulent boundary layer and the expansion of the wake can be clearly observed through flow visualization,especially using the Liutex vortex identification method.展开更多
Considering the demanding of grid requirements for high-Reynolds-number wall-bounded flow,the wall-modeled large-eddy simulation(WMLES)is an attractive method to deal with near wall turbulence.However,the effect of su...Considering the demanding of grid requirements for high-Reynolds-number wall-bounded flow,the wall-modeled large-eddy simulation(WMLES)is an attractive method to deal with near wall turbulence.However,the effect of subgrid-scale(SGS)models for wall-bounded turbulent flow in combination with wall stress models is still unclear.In this paper,turbulent channel flow at Reτ=1000 are numerically simulated by WMLES in conjunction with four different SGS models,i.e.,the wall-adapting local eddy-viscosity model,the dynamic Smagorinsky model,the dynamic SGS kinetic energy model and the dynamic Lagrangian model.The mean velocity profiles are compared with the law of the wall,and the velocity fluctuations are compared with direct numerical simulation data.The energy spectrum of velocity and wall pressure fluctuations are presented and the role of SGS models on predicting turbulent channel flow with WMLES is discussed.展开更多
Wall-modeled large eddy simulation(WMLES)is used to investigate turbulent fluctuations around an axisymmetric body of revolution.This study focuses on evaluating the ability of WMLES to predict the fluctuating flow ov...Wall-modeled large eddy simulation(WMLES)is used to investigate turbulent fluctuations around an axisymmetric body of revolution.This study focuses on evaluating the ability of WMLES to predict the fluctuating flow over the axisymmetric hull and analyzing the evolution of turbulent fluctuations around the body.The geometry is the DARPA SUBOFF bare model and the Reynolds number is 1.2×10^(7),based on the free-stream velocity and the length of the body.Near-wall flow structures and complex turbulent fluctuation fields are successfully captured.Time-averaged flow quantities,such as time-averaged pressure and skin-friction coefficients,and time-averaged velocity profiles on the stern,achieved great agreements between WMLES results and experimental data.Self-similarity of time-averaged velocity defects within a self-similar coordinate up to twelve diameters from the tail.A comprehensive analysis of second-order statistics in the mid-body,stern,and wake regions is condutced.Numerical results agree well with experimental data and previous wall-resolved large eddy simulation(WRLES)results about root mean square(rms)of radial and axial fluctuating velocities at the stern.Turbulent fluctuations including turbulent kinetic energy(TKE)and second-order velocity statistics are identified as dual peak behavior and non-self-similar over the wake length,consistent with previous findings in the literature.This assessment enhances the understanding of WMLES capabilities in capturing complex fluctuating flow around axisymmetric geometries.展开更多
Rotor-stator cavities are frequently encountered in engineering applications such as gas turbine engines.They are usually subject to an external hot mainstream crossflow which in general is highly swirled under the ef...Rotor-stator cavities are frequently encountered in engineering applications such as gas turbine engines.They are usually subject to an external hot mainstream crossflow which in general is highly swirled under the effect of the nozzle guide vanes.To avoid hot mainstream gas ingress,the cavity is usually purged by a stream of sealing flow.The interactions between the external crossflow,cavity flow,and sealing flow are complicated and involve all scales of turbulent unsteadiness and flow instability which are beyond the resolution of the Reynolds-average approach.To cope with such a complex issue,a wall-modeled large-eddy simulation(WMLES)approach is adopted in this study.In the simulation,a 20°sector model is used and subjected to a uniform pre-swirled external crossflow and a stream of radial sealing flow.It is triggered by a convergent Reynoldsaveraged Navier-Stokes(RANS)result in which the shear stress transport(SST)turbulent model is used.In the WMLES simulation,the Smagoringsky sub-grid scale(SGS)model is applied.A scalar transportation equation is solved to simulate the blending and transportation process in the cavity.The overall flow field characteristics and deviation between RANS and WMLES results are discussed first.Both RANS and WMLES results show a Batchelor flow mode,while distinct deviation is also observed.Deviations in the small-radius region are caused by the insufficiency of the RANS approach in capturing the small-scale vortex structures in the boundary layer while deviations in the large-radius region are caused by the insufficiency of the RANS approach in predicting the external crossflow ingestion.The boundary layer vortex and external ingestion are then discussed in detail,highlighting the related flow instabilities.Finally,the large-flow structures induced by external flow ingress are analyzed using unsteady pressure oscillation signals.展开更多
A hybrid noise computation method is presented in this paper.Large-eddy simulation with wall-model equation is proposed to compute the flow field.With a stress-balanced wall-model equation,the near-wall computation co...A hybrid noise computation method is presented in this paper.Large-eddy simulation with wall-model equation is proposed to compute the flow field.With a stress-balanced wall-model equation,the near-wall computation cost of large eddy simulation was effectively reduced.The instantaneous flow variables obtained by the large-eddy simulation were used to compute the noise source terms of the Ffowcs Williams-Hawkings equation.The present method was investigated with two test cases:a single cylinder at Re=10,000 and a rod-airfoil at Re=480,000.The flow quantities and aeroacoustic characteristics were compared with the reference data.The mean velocity profiles and spectra of the flow fluctuations were consistent with data from the literature.When compared with the reference data,the noise computation error was less than 3 dB.The computation results demonstrate the present wall-modeled large eddy simulation is efficient for the noise computation of complex vortex shedding flows.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.52131102)the National Key Research and Development Program of China(Grant Nos.2022YFC2806705,2019YFB1704200).
文摘The flow around an axisymmetric body of revolution(DARPA SUBOFF bare model)at Re=1.2×10^(7)is numerically investigated using the wall-modeled large eddy simulation(WMLES).To evaluate the capabilities of WMLES in such wall-bounded turbulent flows,the effects of the wall stress model and sampling distance are systematically studied.The numerical results of the non-equilibrium wall stress model with an appropriate sampling distance are in good agreement with the experiments in terms of pressure coefficient,skin-friction coefficient,and drag coefficient.On this basis,the thickening of the turbulent boundary layer and the expansion of the wake can be clearly observed through flow visualization,especially using the Liutex vortex identification method.
基金supported by the National Natural Science Foundation of China(Grant No.52131102)the National Key Research and Development Program of China(Grant No.2022YFC2806705)。
文摘Considering the demanding of grid requirements for high-Reynolds-number wall-bounded flow,the wall-modeled large-eddy simulation(WMLES)is an attractive method to deal with near wall turbulence.However,the effect of subgrid-scale(SGS)models for wall-bounded turbulent flow in combination with wall stress models is still unclear.In this paper,turbulent channel flow at Reτ=1000 are numerically simulated by WMLES in conjunction with four different SGS models,i.e.,the wall-adapting local eddy-viscosity model,the dynamic Smagorinsky model,the dynamic SGS kinetic energy model and the dynamic Lagrangian model.The mean velocity profiles are compared with the law of the wall,and the velocity fluctuations are compared with direct numerical simulation data.The energy spectrum of velocity and wall pressure fluctuations are presented and the role of SGS models on predicting turbulent channel flow with WMLES is discussed.
基金supported by the National Natural Science Foundation of China(Grant No.52131102).
文摘Wall-modeled large eddy simulation(WMLES)is used to investigate turbulent fluctuations around an axisymmetric body of revolution.This study focuses on evaluating the ability of WMLES to predict the fluctuating flow over the axisymmetric hull and analyzing the evolution of turbulent fluctuations around the body.The geometry is the DARPA SUBOFF bare model and the Reynolds number is 1.2×10^(7),based on the free-stream velocity and the length of the body.Near-wall flow structures and complex turbulent fluctuation fields are successfully captured.Time-averaged flow quantities,such as time-averaged pressure and skin-friction coefficients,and time-averaged velocity profiles on the stern,achieved great agreements between WMLES results and experimental data.Self-similarity of time-averaged velocity defects within a self-similar coordinate up to twelve diameters from the tail.A comprehensive analysis of second-order statistics in the mid-body,stern,and wake regions is condutced.Numerical results agree well with experimental data and previous wall-resolved large eddy simulation(WRLES)results about root mean square(rms)of radial and axial fluctuating velocities at the stern.Turbulent fluctuations including turbulent kinetic energy(TKE)and second-order velocity statistics are identified as dual peak behavior and non-self-similar over the wake length,consistent with previous findings in the literature.This assessment enhances the understanding of WMLES capabilities in capturing complex fluctuating flow around axisymmetric geometries.
基金This work is supported by the National Natural Science Foundation of China(No.5212201273)the National Science and Technology Major Project of China(No.J2019-III-0003)The CFX software and computation resource supplied by Beijing Super Cloud Computing Center,China are acknowledged.
文摘Rotor-stator cavities are frequently encountered in engineering applications such as gas turbine engines.They are usually subject to an external hot mainstream crossflow which in general is highly swirled under the effect of the nozzle guide vanes.To avoid hot mainstream gas ingress,the cavity is usually purged by a stream of sealing flow.The interactions between the external crossflow,cavity flow,and sealing flow are complicated and involve all scales of turbulent unsteadiness and flow instability which are beyond the resolution of the Reynolds-average approach.To cope with such a complex issue,a wall-modeled large-eddy simulation(WMLES)approach is adopted in this study.In the simulation,a 20°sector model is used and subjected to a uniform pre-swirled external crossflow and a stream of radial sealing flow.It is triggered by a convergent Reynoldsaveraged Navier-Stokes(RANS)result in which the shear stress transport(SST)turbulent model is used.In the WMLES simulation,the Smagoringsky sub-grid scale(SGS)model is applied.A scalar transportation equation is solved to simulate the blending and transportation process in the cavity.The overall flow field characteristics and deviation between RANS and WMLES results are discussed first.Both RANS and WMLES results show a Batchelor flow mode,while distinct deviation is also observed.Deviations in the small-radius region are caused by the insufficiency of the RANS approach in capturing the small-scale vortex structures in the boundary layer while deviations in the large-radius region are caused by the insufficiency of the RANS approach in predicting the external crossflow ingestion.The boundary layer vortex and external ingestion are then discussed in detail,highlighting the related flow instabilities.Finally,the large-flow structures induced by external flow ingress are analyzed using unsteady pressure oscillation signals.
基金National Natural Science Foundation of China under grant Nos.11872230,91952302 and 92052203National Science and Technology Major Project(J2019-II-0006-0026).
文摘A hybrid noise computation method is presented in this paper.Large-eddy simulation with wall-model equation is proposed to compute the flow field.With a stress-balanced wall-model equation,the near-wall computation cost of large eddy simulation was effectively reduced.The instantaneous flow variables obtained by the large-eddy simulation were used to compute the noise source terms of the Ffowcs Williams-Hawkings equation.The present method was investigated with two test cases:a single cylinder at Re=10,000 and a rod-airfoil at Re=480,000.The flow quantities and aeroacoustic characteristics were compared with the reference data.The mean velocity profiles and spectra of the flow fluctuations were consistent with data from the literature.When compared with the reference data,the noise computation error was less than 3 dB.The computation results demonstrate the present wall-modeled large eddy simulation is efficient for the noise computation of complex vortex shedding flows.