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Gravity current propagation up a valley

Published online by Cambridge University Press:  04 December 2014

Catherine S. Jones*
Affiliation:
Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
Claudia Cenedese
Affiliation:
Woods Hole Oceanographic Institution, 266 Woods Hole Road, Woods Hole, MA 02543-1050, USA
Eric P. Chassignet
Affiliation:
Center for Ocean–Atmospheric Prediction Studies (COAPS), Florida State University, 2000 Levy Avenue, Building A, Suite 292, Tallahassee, FL 32306-2741, USA
P. F. Linden
Affiliation:
Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, UK
Bruce R. Sutherland
Affiliation:
Department of Physics, and Department of Earth & Atmospheric Sciences, University of Alberta, Edmonton, AB, T6G 2E1, Canada
*
Email address for correspondence: csjones@ucsd.edu

Abstract

The advance of the front of a dense gravity current propagating in a rectangular channel and V-shaped valley both horizontally and up a shallow slope is examined through theory, full-depth lock–release laboratory experiments and hydrostatic numerical simulations. Consistent with theory, experiments and simulations show that the front speed is relatively faster in the valley than in the channel. The front speed measured shortly after release from the lock is 5–22 % smaller than theory, with greater discrepancy found in upsloping V-shaped valleys. By contrast, the simulated speed is approximately 6 % larger than theory, showing no dependence on slope for rise angles up to ${\it\theta}=8^{\circ }$. Unlike gravity currents in a channel, the current head is observed in experiments to be more turbulent when propagating in a V-shaped valley. The turbulence is presumably enhanced due to the lateral flows down the sloping sides of the valley. As a consequence, lateral momentum transport contributes to the observed lower initial speeds. A Wentzel–Kramers–Brillouin like theory predicting the deceleration of the current as it runs upslope agrees remarkably well with simulations and with most experiments, within errors.

Type
Papers
Copyright
© 2014 Cambridge University Press 

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