Journal of Fluid Mechanics



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


JAMES H. J. BUCHHOLZ a1 and ALEXANDER J. SMITS a1
a1 Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544, USA

Article author query
buchholz jh   [Google Scholar] 
smits aj   [Google Scholar] 
 

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.

(Published Online December 21 2005)
(Received April 4 2005)
(Revised July 14 2005)



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