Improved SST-DES in numerical simulation of mild separation

In the numerical simulation of mild separation by detached eddy simulation (DES) based on shear stress transport (SST) turbulence model, too large turbulent viscosity may translate from the upstream Reynolds averaged navier stokes (RANS) zone to the downstream large eddy simulation (LES) zone by convection, which could restrain the development of resolved turbulence, delay the instability of shear layer and is known as the grey area. Starting from the standard k-equation sub-grid scale model, an improved SST-DES was put forward by preventing the influence of the mixed dependent variables to turbulent viscosity as a result of the original k-equation-like sub-grid model. The numerical study of flow over AS239 airfoil shows that the improved SST-DES keeps the characteristics of delayed detached eddy simulation (DDES) in the boundary layer and increases the accuracy of resolution in the regions far away from the wall at the same time and gets closer results to the experiment compared with SST-DES and SST-DDES.