考虑弹性转轴的扑翼三维气动数值计算

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

通过求解雷诺平均Navier-Stokes方程,研究了同时具有扑动和俯仰运动的三维扑翼气动特性.为了模拟扑翼的弹性特性,在扑翼俯仰轴处设计了扭簧.研究了扑翼平面形状、俯仰弹性轴与质心的相对位置、俯仰刚度变化等参数的影响.结果表明:俯仰角相对扑动角有一个大的相位超前量,且刚度系数越大该超前量越大;考虑了俯仰弹性特征后,计算得到的平均阻力系数减小了60%左右,且升力系数幅值和绕翼根力矩系数的幅值明显减小,而这是判断微型飞行器能否平稳飞行的关键参数.所以,在设计扑翼飞行器时应当考虑其扑翼的俯仰弹性特性,适当设计扑翼的俯仰刚度和俯仰轴的位置对扑翼的空气动力性能至关重要.

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.