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Mixing efficiency in run-down gravity currents

Published online by Cambridge University Press:  15 November 2016

G. O. Hughes  and
P. F. Linden
G. O. Hughes*
Affiliation:
Department of Civil and Environmental Engineering, Imperial College London, South Kensington, London SW7 2AZ, UK
P. F. Linden
Affiliation:
Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, UK
*
†Email address for correspondence: [email protected]
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Abstract

This paper presents measurements of mixing efficiency of the two counter-flowing gravity currents created by symmetric lock exchange in a channel. The novel feature of this work is that the buoyancy Reynolds number of the currents is higher than in previous experiments, so that the mixing is not significantly affected by viscosity. We find that the mixing efficiency asymptotes to 0.08 at high Reynolds numbers. We present a model of the mixing based on the evolution of idealized mean profiles of velocity and density at the interface between the two currents, the results of which are in good agreement with the measurements of mixing efficiency.

JFM classification

Geophysical and Geological Flows: Gravity currents Geophysical and Geological Flows: Stratified flows Turbulent Flows: Stratified turbulence
Type
Papers
Information
Journal of Fluid Mechanics , Volume 809 , 25 December 2016 , pp. 691 - 704
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Copyright
© 2016 Cambridge University Press 

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