风-桥-隧路况下高速车辆的瞬态气动特性及对操纵稳定性影响

When the vehicles exit the tunnel and enter the gorge bridge with strong wind throughout , the sudden change of the flow field and strong unsteady crosswind will change the aerodynamic forces. The change of the aerodynamic drag, lift and pitching moment will change the vertical load and longitudinal force which will influence the corning behavior of the tires, extend the response time of yaw velocity and increase the fluctuation frequency of the yaw velocity. The lag of the response time and the non-continuous change of the wind velocity and direction will let the driver do most wrong judgment and have a floating feeling on the vehicle which will lead to bad influence on the driver’s mentality and harm the traffic safety. Therefore, in current research proposal, the experiments combined with the numerical simulation will be employed to investigate the characteristics of the cross wind around the bridge-tunnel segment of mountain highway, to analyze the unsteady aerodynamic characteristic of the vehicle under the conditions of crosswind-bridge-tunnel, to study the high-speed handling stability with two-way coupled crosswind aerodynamic-crosswind stability, to explore the measurements to improve the crosswind stability under the condition of the bridge-tunnel in mountain highway. The project aims to reveal the characteristics of the wind spectrum of the crosswind around the bridge-tunnel segment of mountain highway，to indicate the change rule of the characteristic of the unsteady aerodynamic and its influence on the handling stability under the condition of crosswind-bridge-tunnel, then provide the theoretical direction for the crosswind stability improvement. The finally aim of the project is to construct an analysis and evaluation framework for the vehicle driving under the condition of crosswind-bridge-tunnel, then provide the theoretical foundation for the setup of the safety facilities around the bridge-tunnel segment of mountain highway.

汽车驶出隧道并经过风力贯穿的峡谷大桥时，流场的突变以及大桥上强烈的非稳态侧向风会使气动力发生改变，其中迎风阻力、升力及纵倾力矩通过改变轮胎的垂直载荷和纵向力，影响轮胎的侧偏特性、延长横摆角速度响应时间及增加波动频率。响应时间的滞后及风速和风向的非连续变化会让驾驶员判断失误或感到汽车发飘，并对驾驶员的心理产生不良影响，危害交通安全。因此，本课题拟采用试验并结合数值计算研究山区高速桥隧相连路段侧风特性；分析风-桥-隧路况下汽车瞬态气动特性；研究风-桥-隧路况下基于气动特性-操纵稳定性双向耦合的高速操纵稳定性；探索桥隧相连路况下改善高速汽车侧风稳定性的措施。本项目旨在揭示山区高速桥隧相连路段侧向风风谱特性，分析风-桥-隧路况下汽车瞬态气动特性变化及其对操纵稳定性影响规律，为改善汽车侧风稳定性提供理论指导，建立桥隧相连路况下侧风行车的分析与评价框架，为山区高速桥隧连接段安全设施的设置提供理论依据。

山区高速公路地形、气候复杂，桥隧密布、桥隧相连的情况大量出现。复杂的桥隧结构会使车辆的运行环境更加复杂，增加高速公路桥隧段交通事故发生率。针对侧风环境下高速车辆通过山区高速桥-隧相连路况下的气动特性及操纵稳定性研究的不足，本项目提出一种基于多体动力学（MBD）和计算流体力学（CFD）动态耦合的方法，构建基于气动特性-操纵稳定性动态耦合的整车动力学模型对汽车侧风气动特性和操纵稳定性进行分析，并开展侧风环境下桥-隧连接路段车辆侧偏安全分析, 为改进汽车的侧风稳定性提供理论指导。.首先搭建了CFD-MBD联合仿真平台，对比分析了采用静态与动态耦合仿真方法计算所得汽车气动力、流场、动力学响应的差异性。通过分析侧风环境下汽车气动特性与动力学响应，探究了应用动态耦合方法的必要性。其次，对轿车在侧风作用下通过跨海大桥桥塔时的气动性能和动力响应进行了深入研究，分析了轿车周围流场与桥塔周围尾涡相互作用的机理，并进一步就侧风类型对气动性能和动力响应的影响进行了讨论；深入探讨了重型货车在峡谷大桥上行驶时的瞬态气动特性以及风场分布，研究了不同结构形式的风障对货车气动特性的影响；考虑到峡谷桥隧段周围风环境的复杂性，分析了轿车驶出隧道、通过桥塔时的气动性能，揭示了特殊地形与不同路况下的超车过程进行了对比仿真分析，探究了相对车速与路面附着系数对主超车再超车过程中气动特性与运动的影响。此外，在考虑牵引车与半挂车转动自由度的基础上，开展了桥隧连接路段厢式半挂车侧风稳定性的相关研究，揭示了牵引车和半挂车不同的气动力、力矩、横摆角和侧向位移的变化规律。最后，设计了基于模糊PID的直接横摆力矩控制方法和主动前轮转向控制策略，对比分析了不同侧风环境下有、无主动控制汽车侧风稳定性。.通过本项目的研究，探索了复杂地形、不同行驶工况以及主动控制策略下汽车瞬态气动特性和操纵稳定性的耦合关系，对于提高汽车行车安全具有重要的学术价值和实际意义。