SAE International CFD Simulation with Automatic Mesh Refinement for the Flow around Simplified Car Models 2012-01-0589

This paper presents simulations for the prediction of the flow around a passenger vehicle. The flow solver used is ISIS-CFD developed by the Numerical Modeling Group of the Fluid Mechanics Laboratory of Ecole Centrale de Nantes. The CFD simulation is carried out with the Explicit Algebraic Stress Model (EASM) turbulence model. For improved precision, the recently developed automatic adaptive grid refinement procedure of the flow solver is used. This procedure is built for unstructured hexahedral grids and naturally supports both isotropic and anisotropic grid refinement to keep the grid sizes small for 3D simulations. The refinement criterion used to indicate the locations of grid refinement is based on the second spatial derivatives of the pressure. This criterion is efficient for flows with strong local vorticity. Three models are used to validate this approach: the Ahmed model, the Willy model and a pickup truck model. The main goal of the simulation is the accurate computation of the trailing vortices of these models. The automatic grid refinement is used to provide the local high grid density needed to create and track these vortices. Comparisons between the numerical results and experimental data are reported.