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

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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.