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On the evolution of the wake structure produced by a low-aspect-ratio pitching panel
Journal article   Peer reviewed

On the evolution of the wake structure produced by a low-aspect-ratio pitching panel

JAMES H. J BUCHHOLZ and ALEXANDER J SMITS
Journal of fluid mechanics, Vol.546(1), pp.433-443
01/10/2006
DOI: 10.1017/S0022112005006865
PMCID: PMC2739398
PMID: 19746198
url
http://doi.org/10.1017/S0022112005006865View
Open Access

Abstract

Flow visualization is used to interrogate the wake structure produced by a rigid flat panel of aspect ratio (span/chord) 0.54 pitching in a free stream at a Strouhal number of 0.23. At such a low aspect ratio, the streamwise vorticity generated by the plate tends to dominate the formation of the wake. Nevertheless, the wake has the appearance of a three-dimensional Kármán vortex street, as observed in a wide range of other experiments, and consists of horseshoe vortices of alternating sign shed twice per flapping cycle. The legs of each horseshoe interact with the two subsequent horseshoes in an opposite-sign, then like-sign interaction in which they become entrained. A detailed vortex skeleton model is proposed for the wake formation.
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