The Effects of Wing Planforms on the Aerodynamic Performance of Thin Finite-Span Flapping Wings

A three-dimensional high-order unstructured dynamic grid based spectral difference (SD) Navier-Stokes (N-S) compressible flow solver with low Mach number preconditioning is used to investigate the effects of wing planforms on the aerodynamics performance of the thin finite-span flapping wings in this paper. Two types of wings, namely the rectangular and bio-inspired wings, are simulated and compared. The formation process of the ubiquitous two-jet-like wake patterns behind the finite-span flapping wing is explained at first. Then the effects of the wing planforms on the aerodynamics performance of the finite-span flapping wings are elucidated in the terms of the evolutions and dynamic interaction between the leading edge vortices (LEV), trailing edge vortices (TEVs) and the wing tip vortices (TVs) as well as the thrust generated by the flapping wings. Different types of LEVs have been discovered for different wing planforms with the flapping motion in the vertical direction, resulting in different aerodynamic performances. A combined plunging and pitching motion is then adopted to enhance the thrust production of the flapping wing, and it increases the amount of the thrust production by about thirty times when compared with the flapping motion only in the vertical direction.