后备轮胎布局对越野车空气动力学效应的影响
Aerodynamic Effects of the Backup Tire Arrangement on a Off-Road Type Passenger Car

为了明确越野车型后备轮胎配置与布局对车辆空气动力学的影响，本文开展了针对MIRA方背标模的空气动力学仿真研究。研究中将后备轮胎布置在车辆尾部8个不同位置并结合贴体和分离两个后备轮胎布局配置进行对比分析。计算表明由于贴体后备轮胎布局使MIRA模型尾部环流流动受阻致使车辆尾部左右两侧存在压力不平衡，同时后备轮胎的引入也导致车辆尾部周围流场的动能损失增大。最终导致车辆的气动阻力增加并且后备轮胎放置位置越远离车辆尾部中央阻力增加越明显。将贴体布局改为分离布局后车辆尾部压力得到明显改善，这是由于车辆尾部与后备轮胎之间的缝隙使车辆左右两侧的空气流动比贴体轮胎布局更加顺畅，结果显示分离布局的车辆风阻系数与基准算例的风阻系数相近，气动性能明显优于贴体轮胎布局。本文的研究结果为越野相关车型外形和空气动力学的开发提供参考。
In order to clarify the influence of the configuration and layout of the off-road vehicle back-up tire on the vehicle aerodynamics, this paper carried out the aerodynamic simulation research for the MIRA squareback model. The investigation positioned the spare tire in eight distinct locations at the vehicle’s rear, with a focus on contrasting two configurations: the body-fitted and the separated configurations. Calculations revealed that the body-fitted configuration in the MIRA model hindered the rear vortex flow, causing pressure discrepancies on either side of the tail, while the inclusion of the spare tire exacerbated the loss of kinetic energy in the flow. These effects ultimately resulted in an increase in the aerodynamic drag of the vehicle, and the drag increase was more pronounced as the tire’s placement moved farther away from the central area. The change from the body-fitted tire layout to the separated tire layout resulted in a significant improvement in vehicle rear pressure, as the gap between the rear vehicle and spare tire allowed air to flow more smoothly between both sides of the vehicle than with the body-fitted setup. The results show that the drag coefficient of the separated configuration is close to that of the benchmark, and the aerodynamic performance is significantly better than that of the body-fitted spare tire configuration. The findings of this study serve as a reference for the development of off-road vehicle designs, particularly in terms of exterior aesthetics and aerodynamics.