Transient aerodynamic characteristics of vans overtaking in crosswinds

Crosswinds affect the aerodynamic characteristics of vehicles involved in overtaking. To investigate such effects, we performed simulations on two identical vans during the overtaking process under different crosswind conditions. The yaw angle between the resultant velocity and the centerline of the overtaken model was varied from 0° to 30°. The results show that the crosswind affects the aerodynamic forces on the two vans significantly, especially on the overtaken van. As the yaw angle increases, the aerodynamic coefficients of the overtaking van increase, but the coefficients of the overtaken van present special patterns at different stages. The pressure fields and flow streamlines for yaw angles β = 0° and 20° were presented to illustrate the potential influence of crosswinds on the two vans. It is obvious that the flow field becomes more complicated under crosswinds, and the varying band of pressure field is expanded. When the front end of the overtaking van exceeds the rear of the overtaken van by a quarter of its body length, the aerodynamic force coefficients of the two vans are considerably large, and the handling stabilities of them decrease greatly. The drivers should pay more attention to safety when driving in crosswinds during the overtaking process.