Flow measurement around flapping dragonflies [Odonata]
1998
Mochizuki, H. (Kagoshima Univ. (Japan). Faculty of Agriculture) | Masuda, K. | Komaki, H.
Flow patterns generated by the flapping of dragonflies (Sympetrum frequents and Pantala flavescens) were investigated in the wind tunnel. The results represented the facts that when the wings were flapping with amplitude of about 80 degrees C, the flow upstream of the body was sucked into the lower pressure region around the body drawing a curved pattern, and in the wake, convex protuberances and concave depressions were brought about on its boundary of the wake due to the alternate downstroke and upstroke of the wings, respectively. Moreover, by visualizing the wake flow, it was confirmed that the flow velocity of the wake was faster than that of the uniform flow outside the wake, resulting in giving lift and thrust to the dragonfly. When the wings are flapping with amplitude of 3-6 degrees C, two vortex sheets are generated consisting of the various types of vortices which are brought forth by the flapping of the fore and hind pairs of wings. Furthermore, due to interference between vortices, the two sheets change their patterns, and then coalesce themselves into a vortex, followed by the disturbed flow regions
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