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Coherent structures in coflowing jets and wakes

Published online by Cambridge University Press:  19 April 2006

A. E. Perry  and
T. T. Lim
A. E. Perry
Affiliation:
Department of Mechanical Engineering, University of Melbourne, Parkville, Victoria 3052, Australia
T. T. Lim
Affiliation:
Department of Mechanical Engineering, University of Melbourne, Parkville, Victoria 3052, Australia
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Abstract

By applying small lateral oscillations to a glass tube from which smoke was issuing, perfectly periodic coflowing jets and wake structures were produced at Reynolds numbers of order 300-1000. These structures remained coherent over long streamwise distances and appeared to be perfectly frozen when viewed under stroboscopic light which was synchronized with the disturbing oscillation. By the use of strobing laser beams, longitudinal sections of the structures were photographed and an account of the geometry of these structures is reported.

When the tube was unforced, similar structures occurred but they modulated in scale and frequency, and their orientation was random.

A classification of structures is presented and examples are demonstrated in naturally occurring situations such as smoke from a cigarette, the wake behind a three-dimensional blunt body, and the high Reynolds number flow in a plume from a chimney. It is suggested that an examination of these structures may give some insight into the large-scale motion in fully turbulent flow.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 88 , Issue 3 , 13 October 1978 , pp. 451 - 463
Copyright
© 1978 Cambridge University Press

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