Abstract: To study the effect of the turbulent flow around 2 cars driving sidebyside on the traffic safety, the turbulent flow field was numerically simulated where the ground effect was imitated by the moving wall boundary condition and the rotating wheel effect was imitated by the rotating wall boundary condition. Taking 2 car models driving sidebyside with a side space of a car as an example, the velocity and pressure distributions on the car models surface were given. The velocity distributions in 3 typical sections and streamline distribution in the right car model wake were presented and discussed. The streamline distributions in the flow field around 2 cars with the side space of 0.1,0.3,0.5,1 and 2 times of car width were compared. The simulated aerodynamic force coefficients were compared with the wind tunnel test value of the single car model with stationary and rotating wheels. The analysis of the sideforce on the right car model showed that with the reducing side spaces, the rapidly increasing side forces push 2 cars to each other, and the safe side space should be 0.5~1.0 times of the car width for the driving and steering safety.

Key words: vehicle aerodynamics, numerical simulation, driving side by side, turbulent flow characteristics, aerodynamic force