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Mixing efficiency in controlled exchange flows

Published online by Cambridge University Press:  26 March 2008

TJIPTO PRASTOWO
Affiliation:
Research School of Earth Sciences, The Australian National University, Canberra, ACT 0200, Australia
ROSS W. GRIFFITHS
Affiliation:
Research School of Earth Sciences, The Australian National University, Canberra, ACT 0200, Australia
GRAHAM O. HUGHES
Affiliation:
Research School of Earth Sciences, The Australian National University, Canberra, ACT 0200, Australia
ANDREW McC. HOGG
Affiliation:
Research School of Earth Sciences, The Australian National University, Canberra, ACT 0200, Australia

Abstract

Turbulence and mixing are generated by the shear between two counter-flowing layers in hydraulically controlled buoyancy-driven exchange flows through a constriction. From direct measurements of the density distribution and the amount of turbulent mixing in steady laboratory exchange flows we determine the overall efficiency of the mixing. For sufficiently large Reynolds numbers the mixing efficiency is 0.11(±0.01), independent of the aspect ratio and other details of constriction geometry, in good agreement with a scaling analysis. We conclude that the mixing in shear flows of this type has an overall efficiency significantly less than the maximum value widely proposed for stratified turbulence.

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Papers
Copyright
Copyright © Cambridge University Press 2008

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