Comparative Study of the use of Finite Volume Method and Lattice Boltzmann Method for Full-Body Automotive Simulations using the DrivAer Model

Abstract

The use of partially scale-resolving CFD (computational fluid dynamics) techniques represents a state-of-the-art approach to aerodynamic design, which is increasingly being adopted by the industry. It still remains crucial to validate the available tools by means of experimental data. The availability of experimental data for the full-scale DrivAer model is still limited when ground simulation is included. New experimental data, including flow field measurements, will be presented in this study. The performance of two commonly used CFD solvers, the finite volume method (FVM)–based open-source Toolbox OpenFOAM and the commercial lattice Boltzmann method (LBM)–based solver PowerFLOW will be analyzed and validated against experimental data. In particular, the flow field around the notchback configuration of the DrivAer model, which includes a shallow detachment region, has proven to be challenging to reproduce in CFD. The results obtained from delayed detached eddy simulation (DDES) exhibit a significant discrepancy with respect to experimental data and unsteady Reynolds-averaged simulations (URANS) in this region. The flow detaches prematurely when DDES is applied. This is caused by an incorrect behavior of the limiter, which is designed to shield the URANS mode from intrusion of large eddy simulation (LES) mode. The recently published enhanced protection (EP) method provides more favorable results in this area. LBM, while generally in good agreement with experiments, predicts a premature separation, most likely due to the Cartesian grid not allowing sufficient resolution. In another challenging area, namely the wheels, the scale-resolving methods show the best results.