Motion Analyses of Flying Insects : Wing Flapping Characteristics of Dragonfly

Abstract

This paper is concerned with the aerodynamic characteristics of flying insects. Some morphological parameters were presented for a variety of insects : mass, wing area and flapping frequency. The relationship between total wing area and flapping frequency was investigated. Dragonflies are used as examples in this report. The self-excited vibration of dragonfly wings was examined in a uniform smooth windstream, and the flow characteristics around a dragonfly were measured with a hot-wire anemometer. Dragonflies of two kinds, Sympetrum frequens and Sympetrum infuscatum, were tested in a wind tunnel. Galloping oscillation of the dragonfly wing was measured by use of an optical displacement detector system. Velocity fluctuations produced by the flying dragonfly in a uniform smooth windstream were measured with a hot-wire anemometer. It was found experimentally that the excitation amplitude of the wing vibration increased when wind velocity exceeded a certain value. It was also found that the waveform and the spectrum of the velocity fluctuation produced behind the dragonfly differed with the location along the wingspan.