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Critical layers in accelerating two-layer flows

Published online by Cambridge University Press:  21 April 2006

Donald B. Altman
Donald B. Altman
Affiliation:
Institute for Naval Oceanography, Stennis Space Center, MS 39529, USA
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Abstract

A series of laboratory experiments on accelerating two-layer shear flows over topography is described. The mean flow reverses at the interface of the layers, forcing a critical layer to occur there. It is found that for a sufficiently thin interface, a slowly growing recirculating region, the ‘acceleration rotor’, develops on the interfacial wave at mean-flow Richardson numbers of O(0.5). This, in turn, can induce a secondary dynamical shear instability on the trailing edge of the wave. A single-mode, linear, two-layer numerical model reproduces many features of the acceleration rotor if mean-flow acceleration and bottom forcing are included. Velocity measurements are obtained from photographs using image processing software developed for the automated reading of particle-streak photographs. Typical results are shown.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 197 , December 1988 , pp. 429 - 451
Copyright
© 1988 Cambridge University Press

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