The paper reports on 3D numerical simulations of unsteady compressible airflow in a blade cascade consisting of flat profiles using a hybrid LES/RANS approach including a transition model.As a first step towards simul...The paper reports on 3D numerical simulations of unsteady compressible airflow in a blade cascade consisting of flat profiles using a hybrid LES/RANS approach including a transition model.As a first step towards simulation of blade flutter in turbomachinery,various incidence angle offsets of the middle blade were modeled.All simulations were run for the flow regime characterized by outlet isentropic Mach number M_(is)=0.5and zero incidence.The results of the LES/RANS simulations(pressure and Mach number distributions)were compared to a baseline RANS model,and to experimental data measured in a high-speed wind tunnel.The numerical results show that both methods overpredict flow separation taking place at the leading edge.In this regard,the hybrid LES/RANS method does not provide superior results compared to the traditional RANS simulations.Nevertheless,the LES/RANS results also capture vortex shedding from the blunt trailing edge.The frequency of the trailing edge vortex shedding in CFD simulations matches perfectly the spectral peak recorded during wind tunnel measurements.展开更多
Unsteady RANS(URANS),hybrid LES/RANS and IDDES simulations were conducted to numerically investigate the velocity field around,and pressures distribution and forces over a square cylinder immersed in a uniform,steady ...Unsteady RANS(URANS),hybrid LES/RANS and IDDES simulations were conducted to numerically investigate the velocity field around,and pressures distribution and forces over a square cylinder immersed in a uniform,steady oncoming flow with Reynolds number Re=21,400.The vortex shedding responses in terms of Strouhal number,the pressure distribution,the velocity profile and the velocity fluctuations obtained by numerical simulations are compared with experimental data.Compared with 2D URANS simulation,3D simulations using hybrid LES/RANS and IDDES models provide more accurate prediction on the responses in the wake,including mean streamwise velocity profile and rms velocity fluctuations.This also results in more accurate prediction of time-averaged surface pressure coefficient on the rear surface obtained by 3D hybrid LES/RANS and IDDES simulations than by URANS simulation.When a hybrid LES/RANS model or IDDES model is used,a more accurate prediction for either pressure coefficient or velocity profile(especially in the far wake region)is not guaranteed by increasing the mesh resolution along the spanwise direction of the square cylinder.展开更多
基金supported by the Czech Science Foundation(GACR)(Grant No.20-11537S)Institutional support RVO:61388998。
文摘The paper reports on 3D numerical simulations of unsteady compressible airflow in a blade cascade consisting of flat profiles using a hybrid LES/RANS approach including a transition model.As a first step towards simulation of blade flutter in turbomachinery,various incidence angle offsets of the middle blade were modeled.All simulations were run for the flow regime characterized by outlet isentropic Mach number M_(is)=0.5and zero incidence.The results of the LES/RANS simulations(pressure and Mach number distributions)were compared to a baseline RANS model,and to experimental data measured in a high-speed wind tunnel.The numerical results show that both methods overpredict flow separation taking place at the leading edge.In this regard,the hybrid LES/RANS method does not provide superior results compared to the traditional RANS simulations.Nevertheless,the LES/RANS results also capture vortex shedding from the blunt trailing edge.The frequency of the trailing edge vortex shedding in CFD simulations matches perfectly the spectral peak recorded during wind tunnel measurements.
基金This work was performed while the author served as the National Institute of Standards and Technology(NIST)Director's Postdoctoral Research AssociateThe funding comes from the Structure Performance for Multi-hazards Progam provided by Materials and Structure Systems Division of Engineering Lab of NIST.
文摘Unsteady RANS(URANS),hybrid LES/RANS and IDDES simulations were conducted to numerically investigate the velocity field around,and pressures distribution and forces over a square cylinder immersed in a uniform,steady oncoming flow with Reynolds number Re=21,400.The vortex shedding responses in terms of Strouhal number,the pressure distribution,the velocity profile and the velocity fluctuations obtained by numerical simulations are compared with experimental data.Compared with 2D URANS simulation,3D simulations using hybrid LES/RANS and IDDES models provide more accurate prediction on the responses in the wake,including mean streamwise velocity profile and rms velocity fluctuations.This also results in more accurate prediction of time-averaged surface pressure coefficient on the rear surface obtained by 3D hybrid LES/RANS and IDDES simulations than by URANS simulation.When a hybrid LES/RANS model or IDDES model is used,a more accurate prediction for either pressure coefficient or velocity profile(especially in the far wake region)is not guaranteed by increasing the mesh resolution along the spanwise direction of the square cylinder.
