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The growth of a grid-generated turbulent mixed layer in a two-fluid system

Published online by Cambridge University Press:  20 April 2006

Harindra J. S. Fernando  and
Robert R. Long
Harindra J. S. Fernando
Affiliation:
Department of Earth and Planetary Sciences, The Johns Hopkins University, Baltimore, Maryland 21218
Robert R. Long
Affiliation:
Department of Earth and Planetary Sciences, The Johns Hopkins University, Baltimore, Maryland 21218
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Abstract

This paper describes a laboratory experiment designed to compare measurements with published theoretical ideas of the mixed-layer growth of a two-layer system in which the turbulence is induced by an oscillating grid. Experimental results show excellent agreement with an earlier theory by one of us (Long), in which the mixed-layer depth D* measured from a virtual origin is given by $D_{*}\sim V_0^{-\frac{7}{11}}K^{\frac{9}{11}}t^{\frac{2}{11}}$, where K is action, t is time and V0 is a characteristic velocity of the problem. The experiments also verify Long's theoretical entrainment relation E = α2Ri−7/4, where E is the entrainment coefficient and $Ri = D^3_{*}\Delta b/K^2$, and Δb is the buoyancy difference between the two layers. The interfacial-layer thickness was observed to be proportional to the depth of the mixed layer, as also predicted by Long. After a certain depth, the entrainment law tends to deviate from Long's theory. The deviation may be due to wall effects.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 133 , August 1983 , pp. 377 - 395
Copyright
© 1983 Cambridge University Press

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