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The evolution of the coherent structures in a uniformly distorted plane turbulent wake

Published online by Cambridge University Press:  26 April 2006

G. A. Kopp ,
J. G. Kawall  and
J. F. Keffer
G. A. Kopp
Affiliation:
Department of Mechanical Engineering, University of Toronto, Toronto, Canada, M5S 1A4
J. G. Kawall
Affiliation:
Department of Mechanical Engineering, University of Toronto, Toronto, Canada, M5S 1A4
J. F. Keffer
Affiliation:
Department of Mechanical Engineering, University of Toronto, Toronto, Canada, M5S 1A4
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Abstract

A plane turbulent wake generated by a flat plate is subjected to a uniform distortion. It is observed that nearly two-dimensional, quasi-periodic coherent structures dominate the distorted wake. Rapid distortion theory, applied to a kinematic vortex model of the coherent structures in the undistorted far wake, predicts many of the effects revealed by a hot-wire anemometry/pattern-recognition analysis of these structures. Specifically, rapid distortion theory predicts reasonably well the observed changes in the ensemble-averaged velocity patterns and the disproportionate amplification of the large-scale coherent structures relative to the smaller-scale ‘isotropic’ eddies. These results are consistent with the view that self-preservation of the distorted wake is not possible because of the selective amplification of the coherent structures, which control the development of the wake. As well, the entrainment rate in the distorted wake increases at a rate greater than that predicted by the self-preservation theory.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 291 , 25 May 1995 , pp. 299 - 322
Copyright
© 1995 Cambridge University Press

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