The Effect of a Gust on the Flapping Wing Performance

The effect of a wind gust on the aerodynamic characteristics of a rigid wing undergoing insect-based flapping motion is studied numerically. The turbulent flow near the flapping wing is described by the 3-D unsteady compressible Reynolds-Averaged Navier-Stokes equations with the Spalart-Allmaras turbulence model. The governing equations are solved using a second-order node-centered finite volume scheme on a hexahedral body-fitted grid that rigidly moves along with the wing. A low-Mach-number preconditioner is used to accelerate the convergence at each time step. The effects of wind gust direction with respect to a wing orientation are investigated. Our numerical results show that the centimeter-scale wing considered in the present study is susceptible to strong downward wind gusts. In the case of frontal and side gusts, the flapping wing can alleviate the gust effect if the gust velocity is less or comparable with the wing tip velocity. For all cases considered, the thrust coefficient returns to its original baseline profile within one full stroke after the gust is removed, thus indicating that the flapping wing can effectively recover from wind gust fluctuations.