This paper presents an experimental investigation of the spanwise flow development on an impulsively started rotating rectangular wing at 45 deg angle of attack. Reynolds numbers of 500 and 15,000 were studied, which correspond to insect and flapping-wing micro-air-vehicle scales, respectively. Stereoscopic particle image velocimetry flowfield measurements were taken at various spanwise locations and sweep angles (angle of rotation from start) on a motor-driven rectangular wing immersed in a seeded water tank. At both Reynolds numbers, the development of the flow was characterized by the formation of strong positive (root-to-tip) and negative (tip-to-root) spanwise flows, which lost strength toward the tip and root, respectively. The negative spanwise flow appeared to be created by the tip vortex, which accelerated fluid from beyond the tip to the root and turned a portion of the positive spanwise flow back on itself, inducing a secondary vortex inboard of the tip vortex and rotating in the opposite sense. Peak positive and negative spanwise flows in both cases were on the order of the wingtip speed. The extent of negative spanwise flow formation on rectangular wings versus tapered wings, as observed in other studies, suggests that perhaps the formation of negative spanwise flow is dependent on wing geometry and the size of the tip vortex.
Positive and Negative Spanwise Flow Development on an Insect-Like Rotating Wing
Journal of Aircraft ; 50 , 5 ; 1321-1332
2013-09-04
12 pages
Article (Journal)
Electronic Resource
English
FULL-LENGTH PAPERS - Positive and Negative Spanwise Flow Development on an Insect-Like Rotating Wing
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