侧风条件下加速超车过程车辆气动特性

利用动网格技术和滑移交界面技术，研究侧风条件下加速超车过程对车辆气动特性的影响，开展两辆厢式货车超车过程的三维瞬态数值模拟. 研究结果表明：主超车和被超车的侧向力系数和横摆力矩系数均随着侧风速度的增大而增大，侧风速度越大，两车的操纵稳定性越差. 与匀速超车过程相比，加速超车过程使主超车的侧向力系数增大，被超车的侧向力系数减小；加速超车过程对主超车侧向力系数的影响幅度大于被超车. 通过分析匀速超车过程和加速超车过程z=1.4 m截面上的压力云图和流线图，得到2种工况下侧向力系数变化的主要原因.

Aerodynamic characteristics of vans during accelerated overtaking process in crosswinds

Three-dimensional transient numerical simulations on two vans were performed by using dynamic mesh technology and sliding interface technology in order to analyze the influence of the accelerated overtaking process on the aerodynamic characteristics of vehicles under crosswind conditions. Results show that both the side force coefficients and the yawing moment coefficients of the overtaking and overtaken vans increase as the crosswind velocity increase. The greater the crosswind velocity is, the poorer the steering stability of the two vans is. The side force coefficients of the overtaking van increase during the accelerated overtaking process compared with the results in the uniform overtaking process, while side force coefficients of the overtaken van decrease. The influence of the accelerated overtaking process on the side force coefficient of the overtaking van is greater than that of the overtaken van. The main reasons for the variation of side force coefficients under two conditions were obtained by analyzing the pressure contours and flow streamlines at z=1.4 m section in the uniform and accelerated overtaking processes.