Studies on Unsteady Aerodynamic Forces on Vehicles under a Fluctuating Side-wind

在风洞中研究了车辆模型在大型悬索桥主塔后尾流中的气动响应（侧力和阻力）。研制了一种使汽车模型高速运行的新装置。我们成功地从非定常侧面提取了一个涡街分量，并对车辆模型的阻力与塔模型侧面的非定常压力进行了同时测量。作为额外的实验，在塔模型后面放置一个分离板可以防止旋涡街在尾流中脱落。这使得幸存的速度梯度的影响很明显，并且对突然陷入均匀流中的飞行器的侧力和阻力也进行了测量。然后，我们准备了五个车辆模型：三个圆柱形（二维）模型和两个箱形（三维）模型，分别具有矩形和方形截面。进一步的研究可以总结如下：(1)圆柱模型在带分流板的塔架尾迹中通过时，气动力受到视攻角、塔架周围气流与飞行器之间的干涉以及流动瞬态特性的影响。在箱形模型的情况下，气动力受迎角的影响。(2)圆柱形或箱形模型的侧力波动对应于塔后涡街引起的风速波动，当车辆离开尾迹时，与涡运动相关的等相角非定常力显著增加。(3)箱形模型上的非定常力对风速变化的响应比圆柱模型上的非定常力响应更快。(4)车辆通过涡街后，车辆的非定常力周期出现紊乱。少

The response of aerodynamic forces( a side and a drag forces ) on a vehicle model passing through a wake behind a main tower of a big suspension bridge has been investigated in a wind tunnel. A new device that makes a vehicle model run with a high speed has been constructed. We successfully extract a component due to a vortex-street from the unsteady side and drag forces on a vehicle model which has been neasured at the same time with an unsteady pressure on the side surface of a tower model. As additional experiments, a splitter-plate placed behind the tower model prevents the vortex street from shedding in the wake. Which makes the effects of the surviving velocity-gradient clear and a side and a drag forces on a vehicle which suddenly immerges in a uniform flow also has been measured.Then we have prepared five vehicle models: three cylindrical (2-dimensional) models and two box (3-dimensional) models with a rectangular and a aquare sections, respectively. The results of the present … More study may be summarized as follows: (1) When a cylindrical model passes through the wake of the tower with a splitter plate, the aerodynamic forces are influenced by the effects of an apparent angle of attack, the interference between the flows around a tower and a vehicle, and the effects of transient characteristics of flow. In the case of box models, the aerodynamic forces are governed by the effects of the angle of attack. (2) The fluctuation in a side-force exerted on a cylindrical or a box models corresponds to the fluctuation in a wind velocity due to the vortex-street behind a tower, and the unsteady forces with a constant phase-angle referred to the vortex-movement remarkably increase when the cehicle gets out of the wake. (3) The unsteady forces on a box model respond more rapidly to the cahnge in wind velocity than ones on a cylindrical model. (4) The periods of the unsteady forces on the vehicles are found to get out of order influenced by its passing through the vortex-street. Less