Combination of Body-Fitted and Embedded Grids for External Vehicle Aerodynamics

Body-fitted and embedded mesh techniques are combined to obtain accurate external aerodynamic solutions for realistic car geometries with minimal user intervention. The key idea is to mesh with typical body-fitted RANS grids the external shape of the vehicle, which is smooth and requires detailed physical modeling. The underhood and undercarriage are treated as embedded surfaces. The flow in this region is massively separated, requiring LES runs and isotropic grids. This makes it a suitable candidate for embedded grids. Comparisons with body-fitted and experimental data for a typical car show that this approach can yield drag predictions with an error less than 5%. Thus, the present approach reduces turnaround times for complete car geometries to 1-2 days, without compromising accuracy.