Flow structure on a rectangular plate subjected to flapping motion

Unsteady motions of wings in biological applications are of particular interest because of the remarkable flight performance of insects and birds. Understanding the flow structure on such wings is central to optimizing their performance. In this study, investigations of the flow structure along the surface of a flapping rectangular flat plate are performed in order to simulate a wing in nature undergoing unsteady motion. Techniques of particle image velocimetry are used to define the complex, quantitative flow patterns on a streamwise-oriented plane that intersects the wing. These flow patterns are determined for variations of the free-stream velocity and the rate at which the wing flaps. The physics of these flow patterns are represented by vorticity contours, vertical velocity contours, and instantaneous velocity vectors.