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

1.空中列车是我们正在研制的一种新型飞行器，它采用了地效翼。它在主翼的翼尖处具有垂直的侧翼，这些侧翼串联布置，以通过侧翼与侧壁之间的翼地效应自动地引导方式调节其横向位置。为了提高飞机的飞行性能，我们进行了一系列的实验研究。在机翼/机翼组合体模型的尖角处加装圆角，可以显著改善模型的气动特性，即显著降低模型的阻力，增加模型的升力。至于升力，可以通过将其与地面效应分离来评估。2.利用双室式小型风洞，对小型轴流风扇进行了性能改善实验。在风机吸力面加装钟形鼠笼后，改善了进口气流状况，风机效率大幅度提高。实验研究了靠近圆柱（主圆柱）的小圆柱（副圆柱）对圆柱（主圆柱）流场的影响。双圆柱的相对位置显著改变了主圆柱上的压力分布和阻力系数。特别是副缸布置在主缸前端时，其影响更大。有时，大的升力是由两个圆柱体的相互作用产生的。这些机制是明确的可视化绕两个圆柱体与烟线方法。

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.