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Aerodynamics of a Bio-inspired Flexible Flapping Wing Micro Air Vehicle

H. Liu


MAVs (micro air vehicles) with a maximal dimension of 15 cm and nominal flight speeds around 10 m/s, normally operate in a Reynolds number regime of 105 or lower, in which most natural flyers including insects, bats and birds fly. Like such natural flyers, the wing structures of MAVs are often flexible and tend to deform by aerodynamic and inertial forces during flight. Consequently, the aero/fluid and structural dynamics of these flyers are closely linked to each other, making the entire flight vehicle difficult to analyze. We have recently developed a hummingbird-inspired, flapping flexible wing MAV with a weight of 2.4 - 3.0 gf and a wingspan of 10 - 12 cm. In this study, we carry out an integrated study of the flexible wing aerodynamics of this flapping MAV by means of an in-house computational fluid dynamic (CFD) solver. A CFD model that has a realistic wing planform and can mimic realistic flexible wing kinematics measured by a high-speed camera filming system is established, which provides a quantitative prediction of unsteady aerodynamics of the four-winged MAV in terms of vortex and wake structures and their relationship with aerodynamic force generation. The CFD-based results show that a leading edge vortex (LEV) and hence a strong negative pressure region are generated on the wings during half stroke. As observed in insect flapping flight, This LEV likely plays a crucial role in the lift and/or thrust force-production in the MAV flight.

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