On the Drag Reduction Optimization of the DrivAer Fastback Model Car with Digital Side Mirror

The traditional side mirrors on an automobile could create a substantial part of drag in the total car aerodynamic design consideration. On some concept cars, digital side mirrors (DSM) have been installed with the aim to reduce the total drag; thus the optimization study of DSM configuration becomes an important task. In this study the benchmark DrivAer fastback model is employed for optimization work of DSM via computational fluid dynamics (CFD) software and simulated with a realistic moving ground and rotating wheel conditions. In order to validate the lift and drag coefficients with existing experimental data, the wheel rotation is implemented through three different kinds of rotating methods: Moving Wall (MW), Multiple Reference Frame (MRF), and Sliding Mesh (SM), while the SM method provides the most accurate results. For optimization work, a concept for the DSM configuration is created, and the objective is to achieve the best drag reduction via various installation positions using the surrogate method based on the Kriging model. The results show that, for the best-achieved side mirror location, a positive effect of drag reduction is observed from increasing the intensity of some specific vortices, and its wake region can be weaker than the original configuration.