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Unsteady separation in a boundary layer produced by an impinging jet

Published online by Cambridge University Press:  20 April 2006

Norbert Didden  and
Chih-Ming Ho
Norbert Didden
Affiliation:
Department of Aerospace Engineering, University of Southern California, Los Angeles, California, 90089-1454 Present address: Institut für Meereskunde an der Universität Kiel, 23 Kiel 1, F. R. Germany.
Chih-Ming Ho
Affiliation:
Department of Aerospace Engineering, University of Southern California, Los Angeles, California, 90089-1454
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Abstract

A vortex-induced unsteady separation was investigated experimentally in the laminar boundary layer produced by an axisymmetric jet impinging normally onto a flat plate. By forcing the air jet, primary ring vortices were periodically generated in the jet shear layer. Phase-locked flow visualization showed that the wall-jet boundary layer separated periodically and evolved into a secondary vortex counter rotating with respect to the primary vortex. The unsteady separation is induced by the primary vortex and moves downstream in the radial mean-flow direction. Phase-averaged hot-wire measurements using a parallel-wire sensor in the vicinity of the unsteady separation provided data for locating the onset of separation in space and time. The data revealed that the unsteady separation originated from a local shear layer which was initiated by the unsteady adverse pressure gradient produced by the primary vortex.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 160 , November 1985 , pp. 235 - 256
Copyright
© 1985 Cambridge University Press

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