Three-dimensional Navier-Stokes simulation of flapping wing with pitching elasticity

The aerodynamic characteristics of a flapping wing with movements of flapping and pitching were investigated by solving unsteady Reynolds-averaged Navier-Stokes equations. A torque spring on pitch axis was used to simulate the pitching elasticity of bird wings. The influences of the platform of flapping wing, the location of gravity center relative to the pitch axis and the torque spring constant on aerodynamic performances were investigated. The results indicate that there would be a large leading phase between the movements of pitching and plunging. The larger spring constant means greater phase difference. After taking the pitching elasticity into consideration, the amplitude of the lift coefficient and that of bending moment at the root of the wing decreased, contributing much to the steady flight of micro air vehicles. Simultaneously the average drag coefficient was reduced by about 60%. Therefore the pitching stiffness and the location of the pitch axis affect the aerodynamic performance a lot and it's very important to consider the pitching elasticity in flapping wing design.