Numerical simulation of the flow field of flapping wings

• Main Authors: Po-Hsiung Li, 李柏勳
• Other Authors: Ching-Shung Chen
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/05982197645112878536

碩士 === 淡江大學 === 航空太空工程學系碩士班 === 96 === This thesis aims at analyzing the aerodynamic characteristics and understanding the lift and thrust generation mechanisms of flapping wings. The commercial software package, FLUENT (6.2.16 version), was utilized to solve the Navier-Stokes equations to obtain the flow fields. The grid system was constructed by a combination of conformal hybrid mesh and dynamic mesh techniques. This grid system allowed realistic simulations of flapping motions of flying creatures. We first simulated a model wing of dragonfly. The trajectory of the flapping motion was simplified using a mathematical model and the dynamic mesh technique was employed. The unsteady flow field and the corresponding lift and drag were obtained. We then simulated the effect of the thickness of the wing on the aerodynamic characteristics. The results show that a thinner wing has better lift and thrust. We also simulated aerodynamic performance of hummingbirds in hovering flight. The simulated results indicate that the lift and thrust change with the aspect ratio of the flapping motion trajectory. If the aspect ratio exceeds 0.2, then there is significant variation of lift and thrust; negative lift is also generated in some part of the flapping cycle. Such large variation of lift degrades the flight stability of hovering. In the future, we expect the numerical techniques developed in this work can be extended to three-dimensional simulations with wing deflection. The trajectory equation of the flapping motion can also be improved to better simulate the motion of flying creatures.