Abstract: The bonnet aerodynamic characteristics of follower vehicle and the flow field in the interspace between vehicles in a two-vehicle platoon are studied, and the flow patterns of scaled model and full scale vehicle model with corresponding Reynolds numbers for two-vehicle platoon are compared by both numerical simulation and model wind tunnel test. The results of simulation are consistent with wind tunnel test for the scaled model, indicating the feasibility of the numerical method adopted. The comparison of the aerodynamic characteristics of platoon at different Reynolds numbers shows that the average static pressure distribution on the bonnet surfaces for both the scaled model and full scale model are basically identical, but on the longitudinal symmetric plane, the tail trace of leading vehicle for full scale model is more up-wards with higher air-flow velocity in bottom area compared with the scaled model. Under unsteady condition and compared with the scaled model, the relative scale of tail vortex of leading vehicle for full scale model apparently smaller, its diffusion is more sufficient with more chaotic state of distribution, and the distribution of pulsating energy on bonnet surface is more disorderly. The movement of vortex in the interspace between vehicles is not a simple displacement but a complex process composed of breakup, pairing and fusing of vortex

Key words: two-vehicle platoon, follower vehicle, bonnet, aerodynamic characteristics, Reynolds number effect, unsteady flow field