Side window clarity and its effect on side mirror visibility plays a major role in safe driving. In view of the problem of side window water pollution when a car is driving in rainy days

combined the aerodynamics and multiphase theory

the Boltzmann method and Lagrangian method are used to solve the transient external flow field and the droplet movement in this paper. Trajectory of the droplet and distribution of the water phase in the side window area are given

the mechanism of water pollution in the side window area is analyzed and the A-column surface is modified. Four different schemes are established

the effects of different schemes on the water film distribution in the side window area are compared and the image processing technology is used to quantify the pollution area. The results show that the four schemes all play a role in reducing water pollution in the side window area. The side window of scheme 2 is the best

the water film coverage is 38.2%

which is decreased by 19.2% compared with the basic model.