A Comparative Study of Different Wheel Rotating Simulation Methods in Automotive Aerodynamics 2018-01-0728

Wheel Aerodynamics is an important part of vehicle aerodynamics. The wheels can notably influence the total aerodynamic drag, lift and ventilation drag of vehicles. In order to simulate the real on-road condition of driving cars, the moving ground and wheel rotation is of major importance in CFD. However, the wheel rotation condition is difficult to be represented exactly, so this is still a critical topic which needs to be worked on. In this paper, a study, which focuses on two types of cars: a fastback sedan and a notchback DrivAer, is conducted. Comparing three different wheel rotating simulation methods: steady Moving wall, MRF and unsteady Sliding Mesh, the effects of different methods for the numerical simulation of vehicle aerodynamics are revealed. Discrepancies of aerodynamic forces between the methods are discussed as well as the flow field, and the simulation results are also compared with published experimental data for validation. Results show that different rotating simulation methods may not affect the aerodynamic drag significantly, but the aerodynamic lift and ventilation drag can be modified in a large range. Furthermore, the lift is shown to be highly sensitive to the position of wheel spokes so two steady methods may result in errors. In conclusion, when CFD simulation is conducted, if only the aerodynamic drag is necessary to be computed, both steady methods can be introduced. If the ventilation drag needs to be taken into consideration, the MRF method is more suitable. However, if the aerodynamic lift must be evaluated, even though much more computational sources will be cost, the Sliding Mesh method is the only one to be advisable. This study can build the base for future works on rotating simulation methods.