Wall-Modeled Large Eddy Simulation and Detached Eddy Simulation of Wall-Mounted Separated Flow via OpenFOAM

Abstract

Considering grid requirements of high Reynolds flow, wall-modeled large eddy simulation (WMLES) and detached eddy simulation (DES) have become the main methods to deal with near-wall turbulence. However, the flow separation phenomenon is a challenge. Three typical separated flows, including flow over a cylinder at ReD = 3900 based on the cylinder diameter, flow over a wall-mounted hump at Rec = 9.36 × 105 based on the hump length, and transonic flow over an axisymmetric bump with shock-induced separation at Rec = 2.763 × 106 based on the bump length, are used to verify WMLES, shear stress transport k-ω DES (SST-DES), and Spalart–Allmaras DES (SA-DES) methods in OpenFOAM. The three flows are increasingly challenging, namely laminar boundary layer separation, turbulent boundary layer separation, and turbulent boundary layer separation under shock interference. The results show that WMLES, SST-DES, and SA-DES methods in OpenFOAM can easily predict the separation position and wake characteristics in the flow around the cylinder, but they rely on the grid scale and turbulent inflow to accurately simulate the latter two flows. The grid requirements of Larsson et al. (δ/Δx,δ/Δy,δ/Δz≈(12,50,20)) are the basis for simulating turbulent boundary layers upstream of flow separation. A finer mesh (δ/Δx,δ/Δy,δ/Δz≈(40,75,40)) is required to accurately predict the separation and reattachment. The WMLES method is more sensitive to grid scales than the SA-DES method and fails to obtain flow separation under a coarser grid, while SST-DES method can only describe the vortices generated by the separating shear layer, but not within the turbulent boundary layer, and overestimates the separation-reattachment zone based on the grid system in this paper.