Research On Transient Aerodynamic Characteristics Of Crossing Vehicles On The Curved Road

With the development of road transport and improvement of the cars traveling speed, the aerodynamic characteristic has become an important factor affecting its stability and security. Most previous and current research focused on the aerodynamic characteristics of isolated vehicle without considering the mutual interference of Multi-car aerodynamic characteristics. In addition, the car, in the corners conditions, will produce an asymmetric aerodynamic, being in a very unstable state. Under the condition of the curve crossing, the flow field around the car will change strongly, which will have great influence in the aerodynamic characteristics. This article will use the STAR-CCM + overset mesh technique to achieve numerical simulation of the curve crossing, exploring the transient aerodynamic characteristics around the car.Transient simulation was conducted for a SAE model with a large number of experimental data using STAR-CCM + overset mesh technique, and the simulation results are compared with wind tunnel test data from the aerodynamic drag and body surface pressure distribution. By comparison, the results obtained from simulation and wind tunnel test showing overall consistency. Therefore, the feasibility of the simulation method was verified.Referring to Highway Route Design specifications-JTG D20-2006, transient simulation of vehicle driving in curved road was conducted, and the simulation results were compared with straight running. As can be seen from the curve charts, side force S, roll moment RM, yawing moment YM have obvious differences, and aerodynamic drag D, lift L, pitching moment PM almost have no difference. As we can see from the pressure scalar around the body, when driving straight, pressure is symmetrical on both body sides, so the next, the vehicle suffered side force is almost zero during straight running state, while traveling on a curve, pressure distribution on both sides of the body showed obvious asymmetry, the vehicle suffered a side force, and aerodynamic side force will cause the roll moment and the yawing moment.Comparing aerodynamic characteristics of curve crossing and straight crossing, we observed that the greatest difference will be the side force S, roll moment RM and yawing moment YM, which have the most dramatic effects on vehicle handling and stability. Under two kind of operating conditions, with the change of the longitudinal position of the two vehicles, the aerodynamic of two driving condition have similar changes, but different from the size of the force, in X / L = 0.25,1.25,2.25 place, there was the presence of extreme values,the aerodynamic force will produce the greatest impact on the stability of the vehicle.Comparing the aerodynamic characteristics of different speed, we found that aerodynamic peak increases with increasing speed, grow linearly as a whole. During curve crossing, the larger, vehicle’s speed is, the greater effect it will have on the other’s aerodynamics. Aerodynamic peak increases with decreasing lateral spacing, grow non-linearly as a whole, smaller the passing spacing was, more dramatic the aerodynamic forces changes.