High-Fidelity Flapping-Wing Aerodynamics Simulations with a Dynamic Unstructured Grid based Spectral Difference Method

A dynamic unstructured grid based high-order spectral difference (SD) method is developed to solve the three dimensional compressible Navier-Stokes (N-S) equations. The capability of the developed solver in handling complex vortex-dominated flow is demonstrated via the simulations of the three dimensional flapping-wing problems at low Reynolds and Mach numbers. The flow fields around flapping wings of different planforms, namely the rectangular and bio- inspired types, with different kinematics are investigated. The formation of a two- jet-like wake pattern after the flapping wing is explained by analyzing the interaction between wake and wing tip vortex structures. Moreover, based on the aerodynamic force results, it is found that the combined plunging and pitching motion can significantly enhance the flapping wing propulsive performance.