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Intrusive gravity currents from finite-length locks in a uniformly stratified fluid

Published online by Cambridge University Press:  10 September 2009

J. R. MUNROE ,
C. VOEGELI ,
B. R. SUTHERLAND ,
V. BIRMAN  and
E. H. MEIBURG
J. R. MUNROE
Affiliation:
Department of Physics, University of Alberta, Edmonton, AB, CanadaT6G 2G7
C. VOEGELI
Affiliation:
Department of Mathematical and Statistical Sciences, University of Alberta, Edmonton, AB, CanadaT6G 2G1
B. R. SUTHERLAND*
Affiliation:
Departments of Physics and Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB, CanadaT6G 2G7
V. BIRMAN
Affiliation:
Department of Mechanical Engineering, University of California, Santa Barbara, CA 93106, USA
E. H. MEIBURG
Affiliation:
Department of Mechanical Engineering, University of California, Santa Barbara, CA 93106, USA
*
†Email address for correspondence: bruce.sutherland@ualberta.ca
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Abstract

Gravity currents intruding into a uniformly stratified ambient are examined in a series of finite-volume full-depth lock-release laboratory experiments and in numerical simulations. Previous studies have focused on gravity currents which are denser than fluid at the bottom of the ambient or on symmetric cases in which the intrusion is the average of the ambient density. Here, we vary the density of the intrusion between these two extremes. After an initial adjustment, the intrusions and the internal waves they generate travel at a constant speed. For small departures from symmetry, the intrusion speed depends weakly upon density relative to the ambient fluid density. However, the internal wave speed approximately doubles as the waves change from having a mode-2 structure when generated by symmetric intrusions to having a mode-1 structure when generated by intrusions propagating near the bottom. In the latter circumstance, the interactions between the intrusion and internal waves reflected from the lock-end of the tank are sufficiently strong and so the intrusion stops propagating before reaching the end of the tank. These observations are corroborated by the analysis of two-dimensional numerical simulations of the experimental conditions. These reveal a significant transfer of available potential energy to the ambient in asymmetric circumstances.

Type
Papers
Information
Journal of Fluid Mechanics , Volume 635 , 25 September 2009 , pp. 245 - 273
Copyright
Copyright © Cambridge University Press 2009

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