Unsteady forces on a two-dimensional wing in plunging and pitching motions

Unsteady fluid dynamic farces acting on a two-dimensional wing in sinusoida l plunging and pitching motions in still water were measured. The measured fluid dynamic forces were larger than those estimated by quasi-steady analy sis, where the effect of unsteady separated vortices on the fluid dynamic f orces is not considered. Vortex capture is a phenomenon related to the larg er fluid dynamic forces in wing motion that is similar to wing motion of re al insects. By using the measured fluid dynamic forces, we identified combi nations of plunging and pitching motions for maximum time-averaged thrust a nd for maximum efficiency.