Aerodynamic Characteristics Of Flapping-wing MAV Simulating Bird Flight

Micro Aero Vehicle (MAV) is a new kind of aircraft. It is small and light, so it is hard to been found. Because of these advantages, it will be used more and more widely in future. Flapping-wing aircraft (Ornithopter) simulating bird's flight can provide lift and thrust at the same time, therefore it can omit the propulsion system and reduce the weight. For this reason, flapping-wing is very suitable for MAV. The lift mechanism of flapping-wing differs much from that of traditional fixed wing. Many researchers tried hard to find out the high-lift mechanism of insect and bird by observing the flap motion of wing and measuring the aerodynamic force produced by flapping wing. In addition, CFD (Computational Fluid Dynamic) method is used more and more widely in the research of the flow field of flapping-wing. For the strongly unsteady characteristic of the flow field of flapping-wing, the traditional vortex lattice method is not more effective. By considering the unsteady boundary condition and fixing wake vortex model, the unsteady vortex lattice method can be used to calculate the unsteady aerodynamics of flapping-wing. In former study of the flapping-wing, the flexibility of the wing was almost neglected. While in the exact flap motion of bird's wing, the deformation of wing is obvious. On the base of former rigid wing model, new flap-wing model is developed by considering the deformation of wing and the change of flapping velocity, so it can simulate the flap motion of bird wing better. By contrasting the computed aerodynamic force of flexible flapping-wing and rigid wing, it is found that if the flexibility is controlled suitable, it can enlarge the lift and thrust effectively. In addition, it's computed that how the aerodynamic force of flexible flapping-wing changes with flap parameters, such as flap angle, flap frequency, and so on. The computed results explained why bird wing have different flap motions in different phases of flight, and provide theory for future design work of flapping-wing MAV. Using one flapping-wing MAV that had accomplished controllable, sustainable flight as model, the force measurement experiment was done in low-speed wind tunnel. This experiment obtained many valuable dates that are similar to the computed result. We also tried flow visualization experiment of flapping-wing, which was the first try in china, and realized the characteristic of flapping-wing's unsteady flow field more directly.