| In recent years, scientists have paid more attention to the development of Micro Air Vehicle (MAV) because of its application in scientific research, exploration and military. Flapping flight which is widely used by birds and insects in nature has been proved to be the most efficient flight mode. In order to develop the MAV that is flexible, high mobility and efficiency like insects, researchers have done a lot of exploration and study on the mechanism of insect flight.In this paper, the mechanism of flapping flight of the insects is reviewed. A click mechanism which can realize the flapping flight is introduced. The aerodynamic performance associated with the click and harmonic mechanisms of a micro air vehicle (MAV) flapping wings are studied using the method of computational fluid dynamics (CFD). Physical models for the micro air vehicle flapping wings were built along wing span. Basing on two dimensional Navier-Stokes (N-S) equation, k-co turbulence model and adaptive dynamic mesh refinement technique, the fluid field around the flapping wings was simulated. The turbulence contours and pressure contours around the wing span direction show that the click mechanism can form a larger pressure difference because of the faster flapping velocity during the downstroke, and when the wings move upward, they can generate a larger lift because of the fully developed vortex. The fluid field around the flapping wings was also simulated in wing chord directions, so that the lift of the click mechanism and harmonic mechanism can be compared. For the wing chord simulation, the rotation of the wing chord was combined with the flapping motion. The aerodynamic analysis along the wing chord direction shows that under the similar period and rotational angles comparing with the harmonic mechanism click mechanism can generate a larger lift force. We also prove that comparing with the harmonic mechanism, the click mechanism is more suitable for the small scale MAV. |
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