Study on the Removal of the Harmful Drag by Controlling the Interference of Boundary-Layer Flows

1.AeroTrain是我们正在研发的一种新型飞行器，它应用了地面机翼效应。它在主翼顶端有垂直的侧翼，通过侧翼和侧壁之间的地翼效应，以导引的方式自动调整其横向位置。我们进行了一系列的实验，通过控制侧翼/机翼干扰来提高气动列车的性能。在侧翼/机翼组合模型的尖角处加装圆角，可以显著改善模型的气动特性，即模型阻力减小，升力显著增大。对于升力，可以通过将圆角与地面效应分开来评估其效果。2.利用双腔式小型风洞，对小型轴流风机进行了性能改进实验。在风机吸力侧安装钟形鼠标，改善了进气条件，提高了效率。但是，在叶轮出口安装导叶，大大提高了叶轮的性能。3.实验研究了圆柱体(主缸)受到较小圆柱体(子柱体)靠近时的流体力特性的影响。两缸相对位置对主缸压力分布和阻力系数有显著影响。尤其是将子缸放置在靠近主缸前部的位置时，影响很大。有时，两个气缸相互作用会产生很大的升力。这些机理是通过用烟丝方法显示两个圆柱体周围的流动来阐明的。

1.Aerotrain is a new type vehicle under development by us, which applies a wing-in-ground effect. It has vertical side wings at the tips of main wings arranged in tandem to regulate automatically its lateral position in a guide way by the wing-in-ground effect between the side wing and the side wall. We performed a series of experiments to improve the performance of Aerotrain by controlling side-wing/wing interaction. Attaching a fillet in the sharp corner of the side-wing/wing combination model, we could considerably improve the aerodynamic characteristics of the model, that is, the drag of the model was decreased and the lift was increased remarkably. As for the lift, the effect of the fillet could be evaluated by separating it from the ground effect.2.Using a double chamber type small wind tunnel, we conducted an experiment with a small axial-flow fan to improve its performance. When installing a bell mouse on the suction side of the fan, the condition of the inlet flow was improved and the efficiency of the fen rose substantially. But, guide vanes which were installed in the exit of the impeller improved the performance too much.3.Fluid-force characteristics of a circular cylinder (a main cylinder) affected by a smaller one (a subcylinder) in close proximity to it were studied experimentally. The relative position of both cylinder changed pressure distribution on the main cylinder and its drag coefficient remarkably. Especially, the effect was very large when the subcylinder was put near the front of the main cylinder. Sometimes, large lift force was produced by the interaction with two cylinders. These mechanisms were made clear by visualizing the flow around two cylinders with a smoke-wire method.