CFD simulation of aerodynamic forces on the DrivAer car model: impact of computational parameters

Automobile designers and engineers are constantly focusing on aerodynamic optimization with the aim of reducing fuel consumption and particulate and gaseous emissions. In the last decade, a generic car body called DrivAer model has been frequently adopted in numerical and experimental investigations. However, the setup of the CFD domain, grid, turbulence model and numerical approach can significantly impact the accuracy of results and requires sensitivity studies. This is the goal of this study for which wind-tunnel (WT) tests and CFD simulations were carried out on the 1:4 reduced-scale DrivAer notchback model. The target parameters were the drag (CD) and lift (CL) coefficients. First, the CFD results were validated with the WT tests. Next, the impact of surface grid resolution, total prism layer height, first prism layer height, growth rate, cell type, upstream and downstream distances, turbulence models, and numerical approaches was systematically investigated. The sensitivity analysis provides a set of guidelines on optimal grid generation. The validation study indicates that a hybrid RANS-LES approach is a good trade-off for an accurate yet economical simulation of the aerodynamic forces. These guidelines are expected to help researchers and practitioners in CFD simulations of car aerodynamics.