A mapping function between the Reynolds-averaged Navier-Stokes mean flow variables and transition intermittency factor is constructed by fully connected artificial neural network(ANN),which replaces the governing equa...A mapping function between the Reynolds-averaged Navier-Stokes mean flow variables and transition intermittency factor is constructed by fully connected artificial neural network(ANN),which replaces the governing equation of the intermittency factor in transition-predictive Spalart-Allmaras(SA)-γmodel.By taking SA-γmodel as the benchmark,the present ANN model is trained at two airfoils with various angles of attack,Mach numbers and Reynolds numbers,and tested with unseen airfoils in different flow states.The a posteriori tests manifest that the mean pressure coefficient,skin friction coefficient,size of laminar separation bubble,mean streamwise velocity,Reynolds shear stress and lift/drag/moment coefficient from the present two-way coupling ANN model almost coincide with those from the benchmark SA-γmodel.Furthermore,the ANN model proves to exhibit a higher calculation efficiency and better convergence quality than traditional SA-γmodel.展开更多
As a universal principle of turbulence cascade,scaling law is important in the research on statistics of turbulence.In the thesis PIV system is used to measure the streamwise velocity vector(u') and the component ...As a universal principle of turbulence cascade,scaling law is important in the research on statistics of turbulence.In the thesis PIV system is used to measure the streamwise velocity vector(u') and the component of vorti-city (dv'/dx) in order to analyze the parameters of SL scaling law in the boundary layer at Reθ=2694 (Reθ is obtained by the momentum thickness and free flow velocity).The method of wavelet and statistics are used in this paper.Then,the parameters of SL scaling law are fitted with the scaling law of extended self similarity,extended of refined similarity hypothesis and a new form of refined similarity.At different distances from the wall and different scale,the results show that the fitted curves of u' is in accordance with experimental curves.For dv'/dx,the fitted curves which are fitted with extended of refined similarity hypothesis and a new form of refined similarity is in accordance with experimental curves.展开更多
基金the financial supports provided by the National Natural Science Foundation of China(Nos.91852112 and 11988102)。
文摘A mapping function between the Reynolds-averaged Navier-Stokes mean flow variables and transition intermittency factor is constructed by fully connected artificial neural network(ANN),which replaces the governing equation of the intermittency factor in transition-predictive Spalart-Allmaras(SA)-γmodel.By taking SA-γmodel as the benchmark,the present ANN model is trained at two airfoils with various angles of attack,Mach numbers and Reynolds numbers,and tested with unseen airfoils in different flow states.The a posteriori tests manifest that the mean pressure coefficient,skin friction coefficient,size of laminar separation bubble,mean streamwise velocity,Reynolds shear stress and lift/drag/moment coefficient from the present two-way coupling ANN model almost coincide with those from the benchmark SA-γmodel.Furthermore,the ANN model proves to exhibit a higher calculation efficiency and better convergence quality than traditional SA-γmodel.
基金Sponsored by the Key Laboratory of Mechanics on Western Disaster and Environment of the Ministry of Education of China
文摘As a universal principle of turbulence cascade,scaling law is important in the research on statistics of turbulence.In the thesis PIV system is used to measure the streamwise velocity vector(u') and the component of vorti-city (dv'/dx) in order to analyze the parameters of SL scaling law in the boundary layer at Reθ=2694 (Reθ is obtained by the momentum thickness and free flow velocity).The method of wavelet and statistics are used in this paper.Then,the parameters of SL scaling law are fitted with the scaling law of extended self similarity,extended of refined similarity hypothesis and a new form of refined similarity.At different distances from the wall and different scale,the results show that the fitted curves of u' is in accordance with experimental curves.For dv'/dx,the fitted curves which are fitted with extended of refined similarity hypothesis and a new form of refined similarity is in accordance with experimental curves.
