Unsteady Aerodynamics of Two Dimensional Insect Flight

Motivated by our interest in unsteady aerodynamics of insect flight, we compute the Navier-Stokes equation around a two dimensional flapping wing. The analysis of unsteady flows in forward flight reveals a mechanism of frequency selection, which results from the two intrinsic time scales associated with the shedding of leading and trailing edge vortices. The predicted preferred frequency scales inversely with the size of the wing, which is consistent with the zoological observation. The computation of hovering flight uncovers an intrinsic mechanism of generating lift by creating a downward jet of counter-rotating vortex pairs. The average computed forces in a generic hovering flight are shown to be sufficient to support typical insect weight.