Abstract: The transient flow field around two simplified shape cars when they meet oppositely sidebyside in tunnel was simulated by means of the sliding interface and the moving mesh features offered by a commercial computational fluid dynamics(CFD) software. The differences between the transient and the steady simulations, the transient aerodynamic characteristics(including the wake structure and the aerodynamic coefficients) of the cars, the interaction between the air flow and the cars under the condition of opposite meet sidebyside were analyzed. It was found that it is feasible to use CFD to simulate the transient aerodynamic phenomenons and the aerodynamic coefficients of the cars change sharply like sinusoidal functions. The aerodynamic forces on the cars when they meet have significant effect on the car handling stability.

Key words: vehicle aerodynamics, computational fluid dynamics, opposite meet sidebyside, transient character