Flows experiencing laminarization and retransition are universal and crucial in many engineering applications.The objective of this study is to conduct an uncertainty quantification and sensitivity analysis of turbule...Flows experiencing laminarization and retransition are universal and crucial in many engineering applications.The objective of this study is to conduct an uncertainty quantification and sensitivity analysis of turbulence model closure coefficients in capturing laminarization and retransition for a rapidly contracting channel flow.Specifically,two commonly used turbulence models are considered:the Spalart-Allmaras(SA)one-equation model and the Menter Shear Stress Transport(SST)two-equation model.Thereby,a series of steady Reynolds Averaged Navier-Stokes(RANS)predictions of aero-engine intake acceleration scenarios are carried out with the purposely designed turbulence model closure coefficients.As a result,both SA and SST models fail to capture the retransition phenomenon though they achieve pretty good performance in laminarization.Using the non-intrusive polynomial chaos method,solution uncertainties in velocity,pressure,and surface friction are quantified and analyzed,which reveals that the SST model possesses much great uncertainty in the non-laminar regime,especially for the logarithmic law prediction.Besides,a sensitivity analysis is performed to identify the critical contributors to the solution uncertainty,and then the correlations between the closure coefficients and the deviations of the outputs of interest are obtained via the linear regression method.The results indicate that the diffusion-related constants are the dominant uncertainty contributors for both SA and SST models.Furthermore,the remarkably strong correlation between the critical closure coefficients and the outputs might be a good guide to recalibrate and even optimize the commonly used turbulence models.展开更多
A Legendre spectral approximation based on the pressure stabilization method for non-periodic, unsteady Navier-Stokes equations is considered. The generalized stability and the convergence are proved strictly. The app...A Legendre spectral approximation based on the pressure stabilization method for non-periodic, unsteady Navier-Stokes equations is considered. The generalized stability and the convergence are proved strictly. The approximation results in this paper are also useful for other non-linear problems.展开更多
The subject of the paper is the numerical simulation of the interaction of two-dimensional incompressible viscous flow and a vibrating airfoil with large amplitudes.The airfoil with three degrees of freedom performs r...The subject of the paper is the numerical simulation of the interaction of two-dimensional incompressible viscous flow and a vibrating airfoil with large amplitudes.The airfoil with three degrees of freedom performs rotation around an elastic axis,oscillations in the vertical direction and rotation of a flap.The numerical simulation consists of the finite element solution of the Reynolds averaged Navier-Stokes equations combined with Spalart-Allmaras or k−ω turbulence models,coupled with a system of nonlinear ordinary differential equations describing the airfoil motion with consideration of large amplitudes.The time-dependent computational domain and approximation on a moving grid are treated by the Arbitrary Lagrangian-Eulerian formulation of the flow equations.Due to large values of the involved Reynolds numbers an application of a suitable stabilization of the finite element discretization is employed.The developed method is used for the computation of flow-induced oscillations of the airfoil near the flutter instability,when the displacements of the airfoil are large,up to±40 degrees in rotation.The paper contains the comparison of the numerical results obtained by both turbulence models.展开更多
基金co-supported by the Youth Program of the National Natural Science Foundation of China (No. 11902367)the Youth Program of Natural Science Foundation of Hunan Province, China (Nos. S2021JJQNJJ2519 and S2021JJQNJJ2716)the Science and Technology Research and Development plan of China National Railway Group, China (Nos. P2020J025 and P2021J036)
文摘Flows experiencing laminarization and retransition are universal and crucial in many engineering applications.The objective of this study is to conduct an uncertainty quantification and sensitivity analysis of turbulence model closure coefficients in capturing laminarization and retransition for a rapidly contracting channel flow.Specifically,two commonly used turbulence models are considered:the Spalart-Allmaras(SA)one-equation model and the Menter Shear Stress Transport(SST)two-equation model.Thereby,a series of steady Reynolds Averaged Navier-Stokes(RANS)predictions of aero-engine intake acceleration scenarios are carried out with the purposely designed turbulence model closure coefficients.As a result,both SA and SST models fail to capture the retransition phenomenon though they achieve pretty good performance in laminarization.Using the non-intrusive polynomial chaos method,solution uncertainties in velocity,pressure,and surface friction are quantified and analyzed,which reveals that the SST model possesses much great uncertainty in the non-laminar regime,especially for the logarithmic law prediction.Besides,a sensitivity analysis is performed to identify the critical contributors to the solution uncertainty,and then the correlations between the closure coefficients and the deviations of the outputs of interest are obtained via the linear regression method.The results indicate that the diffusion-related constants are the dominant uncertainty contributors for both SA and SST models.Furthermore,the remarkably strong correlation between the critical closure coefficients and the outputs might be a good guide to recalibrate and even optimize the commonly used turbulence models.
文摘A Legendre spectral approximation based on the pressure stabilization method for non-periodic, unsteady Navier-Stokes equations is considered. The generalized stability and the convergence are proved strictly. The approximation results in this paper are also useful for other non-linear problems.
基金This research was supported under the grants of the Czech Science Foundation No.P101/11/0207(J.Horacek)and 13-00522S(M.Feistauer,P.Svacek)。
文摘The subject of the paper is the numerical simulation of the interaction of two-dimensional incompressible viscous flow and a vibrating airfoil with large amplitudes.The airfoil with three degrees of freedom performs rotation around an elastic axis,oscillations in the vertical direction and rotation of a flap.The numerical simulation consists of the finite element solution of the Reynolds averaged Navier-Stokes equations combined with Spalart-Allmaras or k−ω turbulence models,coupled with a system of nonlinear ordinary differential equations describing the airfoil motion with consideration of large amplitudes.The time-dependent computational domain and approximation on a moving grid are treated by the Arbitrary Lagrangian-Eulerian formulation of the flow equations.Due to large values of the involved Reynolds numbers an application of a suitable stabilization of the finite element discretization is employed.The developed method is used for the computation of flow-induced oscillations of the airfoil near the flutter instability,when the displacements of the airfoil are large,up to±40 degrees in rotation.The paper contains the comparison of the numerical results obtained by both turbulence models.
