紊流影响下车-桥系统气动力特性风洞试验

为了研究横风作用下紊流参数对车-桥系统气动力特性的影响,以典型32 m简支梁桥和CRH2列车头车为背景,首先根据阻塞比要求设计几何缩尺比为1：25的桥梁和列车测压试验模型;然后通过在风洞试验段入口处采用格栅条被动紊流发生装置,模拟一系列紊流风场;最后开展不同工况下车-桥组合风洞动态测压试验,测试列车和桥梁表面风压,并积分获得列车和桥梁气动力。基于此,分析了双线轨道不同位置下,顺风向紊流度、紊流积分尺度对列车表面风压和车-桥气动力分布的影响规律,并讨论了风攻角对车-桥气动力系数的影响。结果表明：列车表面平均风压系数随紊流度的增加而减小,紊流风场中列车和桥梁气动侧力（阻力）系数均小于均匀流场;紊流度对迎风侧轨道列车的影响更为显著,而对车头气动力特性影响较小,车身侧力（阻力）系数随紊流度增加而显著降低,升力系数和力矩系数随紊流度的变化规律并不显著;桥梁气动力系数对紊流度变化的敏感程度小于列车,其侧力（阻力）系数并非随紊流度的增大而单调减小,升力系数随紊流度增加而增大,力矩系数随紊流度的变化规律并不明显;车-桥气动力系数受紊流积分尺度的影响小于紊流度,桥梁侧力（阻力）系数受影响程度大于升力系数和力矩系数;列车位于背风侧轨道时,车-桥气动力系数随紊流积分尺度变化的敏感程度小于列车位于迎风侧轨道;风攻角和紊流参数对车-桥气动力特性的影响是相互独立的,且受列车路线布置方式影响不大。研究结果为紊流风场下的行车安全性提供了数据和资料。

Wind Tunnel Test of Aerodynamic Force Characteristics on Train-bridge System in the Presence of Turbulence

To investigate the influence of turbulence flow parameters on the aerodynamic characteristics of vehicle-bridge system subject to crosswinds, a typical supported girder with a 32-m width and a CRH2 vehicle were used as research objects in this study. First, a girder and vehicle test models were designed. Based on the blocking ratio, and the scale of the models was 1:25. Next, different types of turbulence fields were established in a wind tunnel by using grids at the inlet of the wind tunnel. Finally, through wind tunnel tests, wind pressures on the bridge and vehicle were obtained. Aerodynamic forces and moment coefficients were calculated by integral method. Based on this, the influences of turbulence intensity, turbulence integral scale, and wind attack angle on the wind pressure and aerodynamic force were analyzed. Results show that in turbulence flow fields, the mean wind pressure coefficients on the vehicle decrease with increasing turbulence, and the aerodynamic side force coefficients of the vehicle are smaller than those in a uniform flow field. Turbulence intensity has a more pronounced effect on the windward rail. The effect of turbulence intensity on the head is less than that on the body of the vehicle, and the side force coefficient of the vehicle body decreases significantly with increasing turbulence intensity. However, turbulence intensity has little effect on lift force and the moment coefficient of the vehicle. The aerodynamic force coefficients of the bridge are less sensitive to the turbulence intensity than to those of vehicle, and the variation in the drag force coefficient of the bridge does not always decrease with increasing turbulence intensity. In addition, the lift coefficient increases with increasing turbulence intensity, and the variation in the moment coefficient with turbulence intensity is negligible. The turbulent integral scale has a greater effect on the bridge side force (drag force) coefficient than the lift and moment coefficients. By contrast, the influence of the turbulent integral scale on the aerodynamic force coefficients of bridges and vehicles is less significant than that of the turbulent intensity. The sensitivity of the vehicle's aerodynamic coefficients with the turbulent integral scale on the leeward rail is less than that of the windward rail. Wind attack angles affect the aerodynamic coefficients of the vehicle-bridge system, which is more prominent for vehicles on the leeward track. The effects of wind attack angles and turbulence flow parameters on the aerodynamic characteristics of the vehicle-bridge system are independent of each other, and they are insensitive to the effects of different tracks. The conclusions derived from this study can be a reference for future studies of the safety of high-speed railway trains under crosswinds in turbulent flow fields.