Abstract
A butterfly flies with beating a pair of wings. In order to estimate the aerodynamic forces acting on the wings, the heating motion of the wings was simulated by the flapping motion of a triangular plate and its mirror image, caused by free falling of the plate about a flapping hinge in water tank, and was analyzed by observing the plate motion filmed with a still camera and a cine-camera. By painting the plate with a soluble dye the vortices generated at leading edges and vortices shed at trailing edge of the plate were visualized during the flapping motion. The configuration and position of these vortices were utilized to analyze the induced velocity on the plate.
