Large eddy simulation of flow around an airfoil

Abstract

A Large Eddy Simulation (LES) of a turbulent flow over the A-airfoil near stall at a chord Reynolds number of 2.1 x 10 is performed and compared with windtunnel experiments. This configuration still constitutes a challenging test case for Reynolds Average Navier-Stokes (RANS) simulation and LES due to the complexity of the suction side boundary layer: an adverse pressure gradient creates successively a laminar separation bubble, a turbulent reattachment and a turbulent separation near the trailing edge. To handle this high Reynolds number flow with LES on available supercomputer, a local mesh refinement technique and a discretization of the convective fluxes are developed in a block-structured finite volume code to reduce the total number of grid points and the numerical dissipation acting on the small scales, respectively. Influence of Subgrid Scale Modelling (SGS) is assessed through the comparisons of explicit Selective Mixed Scale Model (SMSM) and implicit MiLES model results. Moreover the solution sensitivity to grid refinement and spanwise extent is investigated. With the use of the largest grid (7.2 x 10 cells) and SMSM model, the computed mean and fluctuating velocity profiles compares favourably with experimental measurements, which constitutes to the authors knowledge the first satisfying LES of this complex flow.