Application of Filter-SST method in airfoil deep stall simulation

To improve the calculation precision of the original shear stress transport (SST) two-equation turbulence model, the filter factor of the large eddy simulation (LES) and SST formula are combined. The computation zone is splitted by the filter factor, through which a stable flow near the wall is controlled by the turbulence model while the flow far from the wall is simulated by LES. The advantage of this method in comparison with the classic hybrid RANS/LES methods is that the filter can be chosen without depending on grid scale, resulting in a decrease of the probability of grid induced separation. The deep stall of NACA0021 airfoil is simulated by using the filter SST, unsteady Reynolds-averaged Navier-Stokes (URANS) and SST-DES. The simulation result demonstrates that the impulse in the separated region can be effectively activated by the filter SST method. The phenomenon shows the three dimension characteristics of separation. Meanwhile, the result of the test case is more precise than that obtained by the URANS method and it matches well with the result obtained by experiment.