Modelled and resolved turbulent stresses around a circular cylinder using DES

Abstract

Massively separated flows at high Reynolds numbers over a circular cylinder are simulated numerically using an in-house CFD code called Dynamic Grid Detached Eddy Simulation (DG-DES). Turbulent kinetic energy is approximated using Bradshaw’s hypothesis [2] and normal and shear stresses are computed. Comparison of time averaged normalized velocity and resolved stresses is done with the experimental data [3] at Re = 1.4 × 105. A comparison of the modelled and resolved turbulent stresses is also made at the Re = 8 × 106.The comparison of computed normalized velocity and turbulent Reynolds stresses with the available experimental data shows good results. It shows that the DES method has preserved the flow physics well while switching from RANS to LES mode. It also shows that normal and shear stress computed using the Bradshaw’s approximation to compute kinetic energy gives good results. The comparison of modelled and resolved turbulent stresses shows that the modelled stresses are concentrated in the boundary layer and shear layer region (RANS regions) and the resolved stresses are dominant in the separated flow region (LES region).