Development of Micro Air Vehicles to fly freely in turbulence

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In order to clarify the flight mechanism of insects, effects of incoming flow turbulence on aerodynamic forces of a micro air vehicle were measured experimentally focusing on the relationship between aerodynamic force and flow field around the micro air vehicle with a turbulence generator and the mechanical flapper. In the case of a fixed-wing, the angle of attack of flow was changed by the incoming flow turbulence. As a result, the aerodynamic force is reducing with increasing the intensity of the incoming flow turbulence. On the other hand, in the case of mechanical flapper, the flow fields were almost the same as both of the laminar and turbulent incoming flow. As a result, the aerodynamic lifting forces were almost the constant in turbulent flow. It is because that effect of the low Reynolds number flow and large reduced frequency of the insect' s flight. The separated vortices stay around the flapping wings. Therefore, these vortices generate the aerodynamic force act on the wings. There is a small influence for turbulence ; therefore this method is advantageous in comparison with a fixed-wing. It reveals that the wake capture is important to control and stable flight of insects. Moreover, it is necessary to optimize the ratio of flapping speed and flight speed for stable flight.