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The hydraulics of two flowing layers with different densities

Published online by Cambridge University Press:  21 April 2006

Laurence Armi
Laurence Armi
Affiliation:
Scripps Institution of Oceanography, La Jolla, California 92093
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Abstract

This is a theoretical and experimental study of the basic hydraulics of two flowing layers. Unlike single-layer flows, two-layer flows respond quite differently to bottom depth as opposed to width variations. Bottom-depth changes affect the lower layer directly and the upper layer only indirectly. Changes in width can affect both layers. In fact for flows through a contraction control two distinct flow configurations are possible; which one actually occurs depends on the requirements of matching a downstream flow. Two-layer flows can pass through internally critical conditions at other than the narrowest section. When the two layers are flowing in the same direction, the result is a strong coupling between the two layers in the neighbourhood of the control. For contractions a particularly simple flow then exists upstream in which there is no longer any significant interfacial dynamics; downstream in the divergent section the flow remains internally supercritical, causing one of the layers to be rapidly accelerated with a resulting instability at the interface. A brief discussion of internal hydraulic jumps based upon the energy equations as opposed to the more traditional momentum equations is included. Previous uniqueness problems are thereby avoided.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 163 , February 1986 , pp. 27 - 58
Copyright
© 1986 Cambridge University Press

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