PANS VS. LES FOR COMPUTATIONS OF THE FLOW AROUND A 3D BLUFF BODY

Paper in proceeding, 2008

This paper presents comparisons between recently proposed Partially-Averaged Navier-Stokes (PANS) method with the Large Eddy Simulation (LES) for the flow around the Ahmed bluff body. PANS model changes seamlessly from Reynolds- Averaged Navier-Stokes (RANS) to the direct numerical solution of the Navier-Stokes equations (DNS) as the unresolved-to-total ratios of kinetic energy and dissipation are varied. The parameter which determines the unresolved-to-total kinetic energy ratio is defined based on the grid spacing and it is dynamically adjusted at each point at the end of every time step. The main target of this paper is to show if PANS obtains comparable results with LES calculations on finer meshes and improves results on coarser meshes. In other words, the question to be answered is whether PANS can provide the optimum solution for every computational mesh. This will be achieved by comparing PANS calculations on two different computational meshes: 3.4 mil.(grid A), and 8.0 mil. (grid B), with LES calculations on grid A and additional two grids consisting of 9.5 mil. cells (grid C) and 16.5 mil. cells (grid D).