Energy consumption and environmental pollution problems have become increasingly prominent in China. The drag reduction of vehicles is an effective method to improve the fuel economy of cars and reduce greenhouse emissions. In this paper, based on the MIRA squareback model, the influence of the shapes, arrangements, layout positions, and dimensions of the non-smooth units on the aerodynamic characteristics of vehicles are investigated through the computational fluid dynamics (CFD) method. The depth, longitudinal spacing, and horizontal spacing are taken as the design variables and the aerodynamic drag coefficient is used as the optimization objective. The optimal Latin hypercube experimental design method is adopted to select sample points, and the response values of each experiment sample point are calculated through the integrated platform in Isight software. According to the response values, the Kriging approximation model is built and validated. Furthermore, the multi-island genetic algorithm is applied to optimize the dimensions of pit non-smooth units. The aerodynamic characteristics of the smooth surface model and the optimized non-smooth surface model under steady crosswind are conducted using numerical simulation. The findings obtained from the investigation will provide a certain reference for the application of non-smooth units in the field of automobiles.
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