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Barotropically induced interfacial waves in two-layer exchange flows over a sill

Published online by Cambridge University Press:  14 November 2007

M. ELETTA NEGRETTI ,
DAVID Z. ZHU  and
GERHARD H. JIRKA
M. ELETTA NEGRETTI
Affiliation:
Institute for Hydromechanics, University of Karlsruhe, Germany
DAVID Z. ZHU
Affiliation:
Department of Civil and Environmental Engineering, University of Alberta, Canada
GERHARD H. JIRKA
Affiliation:
Institute for Hydromechanics, University of Karlsruhe, Germany
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Abstract

Two-layer exchange flows are observed in the channels/straits connecting two water bodies of different densities. This study examines the nature of the barotropic forcing and its effect on the interfacial waves in two-layer exchange flows over a smooth/break underwater sill. Experiments were conducted with different initial conditions, distinguishing the case of hydrostatic disequilibrium and the case of a global pressure-balanced state. The experiments demonstrate that the baroclinic exchange flow is dominated by the barotropic-forcing-induced oscillations. A simplified barotropic model is developed to predict the period of the barotropic oscillation with an excellent agreement with experimental measurements. Detailed velocity and flow-rate measurements also indicate the importance of the barotropic forcing in exchange flows. The effect of the superimposed barotropic forcing on the interfacial wave characteristics is also investigated. Large two-dimensional surge-like structures are observed during the experiments, whose generation is shown to be related to the flow-rate oscillations. The length scales of these structures is comparable with the total water depth and is shown to increase with increasing Reynolds numbers.

Type
Papers
Information
Journal of Fluid Mechanics , Volume 592 , 10 December 2007 , pp. 135 - 154
Copyright
Copyright © Cambridge University Press 2007

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