抄録
The purpose of the present study is to clarify the dynamic behaviors of butterfly wings, such as the trajectory of butterfly wings and flapping angle of butterfly by flight observation. Moreover, we visualize flow around the butterfly with particles, process images and clarify the vortex flow structure on the butterfly wings. In particular, we draw attention to the tip vortices rolled up from the wing tip and discuss on the three-dimensional vortex flow structure on the butterfly wing. Cynthia cardui wings have elastic behaviors not only in the wing chord direction but also in the wing span direction. The flapping angle of the Cynthia cardui wing showed triangular wave and the time ratio for moving upward and downward of the flapping wing was approximately 1:1.25. The vortex flow called "delayed stall" which is important for insect flight, grew in the wing chord direction of the Cynthia cardui. A pair of vortices rolled up from vortex tip was formed not only in the chord center of the wing but also in the leading and trailing edge when the downstroke of the wing started from the top dead-center position. Therefore, it is considered that a cylindrical vortex rolled up from the vortex tip at downstroke in the flapping motion.
