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The Structure and Control of a Turbulent Reattaching Flow

Sigurdson, L. W. and Roshko, A. (1988) The Structure and Control of a Turbulent Reattaching Flow. In: Turbulence Management and Relaminarisation. Springer , Berlin, pp. 497-514. ISBN 978-3-642-83283-3.

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An experimental study was made of the effect of a periodic velocity perturbation on the separation bubble downstream of the sharp-edged blunt face of a circular cylinder aligned coaxially with the free stream. Velocity fluctuations were produced with an acoustic driver located within the cylinder and a small circumferential gap located immediately downstream of the fixed separation line to allow communication with the external flow. The flow could be considerably modified when forced at frequencies lower than the initial Kelvin-Helmholtz frequencies of the free shear layer, and with associated vortex wavelengths comparable to the bubble height. Reattachment length, bubble height, pressure at separation, and average pressure on the face were all reduced. The effects on the large-scale structures were studied on flow photographs obtained by the smoke-wire technique. The forcing increased the entrainment near the leading edge. It was concluded that the final vortex of the shear layer before reattachment is an important element of the flow structure. There are two different instabilities involved, the Kelvin-Helmholtz instability of the free shear layer and the “shedding” type instability of the entire bubble. A method of frequency scaling is proposed which correlates data for a variety of bubbles and supports an analogy with Karman vortex shedding.

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Additional Information:© 1988 Springer-Verlag Berlin Heidelberg. Financial support for this research was provided by the Office of Naval Research. contract number N00014-76-C-0260. Travel funds were provided by the National Science Foundation.
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Office of Naval Research (ONR)N00014-76-C-0260
Record Number:CaltechAUTHORS:20170731-100953029
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:79588
Deposited By: Tony Diaz
Deposited On:01 Aug 2017 19:44
Last Modified:15 Nov 2021 17:49

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