抄録
Dragonflies have high flight performance in spite of small-size and can do many types of flight. Therefore, dragonflies are one of the best models for designing of micro air vehicle (MAV). Previous studies have shown that vortexes are important for the flight of insects including dragonflies. However, the effect of vortexes on aerodynamic forces is not clarified quantitatively. This study is focused on vorticity around flapping wing. In this study, vorticity and circulation around flapping wing are investigated with a particle image velocimetry. Then, lift force are calculated from the circulation on the basis of Kutta-Joukowski theorem, and is compared with experimental values. As a result, the vorticity and circulation varied with the flapping angle. The lift force was generated when the clockwise circulation was generated, and the thrust force was generated when the anticlockwise circulation was generated. During downstroke, lift force calculated by Kutta-Joukowski theorem were about 40 percent of the experimental value. In contrast, during upstroke, thrust force calculated were about 80 percent of the experimental value. It is suspected that the dragonfly flight uses the vortexes around wings in upstroke particularly.
