Hostname: page-component-cd9895bd7-gvvz8 Total loading time: 0 Render date: 2025-01-03T23:27:31.658Z Has data issue: false hasContentIssue false
  • English
  • Français

Laboratory modelling of the effects of temporal changes of estuarine-fresh-water discharge rates on the propagation speed of oceanographic coastal currents

Published online by Cambridge University Press:  29 November 2010

PETER J. THOMAS  and
P. F. LINDEN
PETER J. THOMAS*
Affiliation:
Fluid Dynamics Research Centre, School of Engineering, University of Warwick, Coventry CV4 7AL, UK
P. F. LINDEN
Affiliation:
Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, Wilberforce Road, Cambridge CB3 0WA, UK
*
†Email address for correspondence: pjt1@eng.warwick.ac.uk
Get access Rights & Permissions [Opens in a new window]

Abstract

In this paper, results of laboratory experiments simulating buoyancy-driven coastal currents produced by estuarine discharges into the ocean, are discussed. The responses of the propagation speeds of the currents to increases and decreases of the volumetric discharge rate at the source are investigated. For increasing discharge rate, we find that the mean speed of the current head displays a sharp rise some time after the source discharge condition has changed. In contrast, a decrease of the current speed following a decreasing discharge rate proceeds gradually. The current speed after acceleration or deceleration is found to be equal to the speed that would be expected had the discharge been at the higher or lower rate from the start of the experiment. The relative speed at which the information of the changed discharge condition at the source approaches the advancing current head from upstream, for both increasing and decreasing discharge rates, is found to be approximately one to three times the mean speed of the current. Further, we find that this transmission speed is 0.82±0.20 times the propagation speed of a linear, long interfacial Kelvin wave.

JFM classification

Geophysical and Geological Flows: Geophysical and Geological Flows Geophysical and Geological Flows: Gravity currents Geophysical and Geological Flows: Rotating flows
Type
Papers
Information
Journal of Fluid Mechanics , Volume 664 , 10 December 2010 , pp. 337 - 347
Copyright
Copyright © Cambridge University Press 2010

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

Avicola, G. & Huq, P. 2002 Scaling analysis for the interaction between a buoyant coastal current and the continental shelf: experiments and observations. J. Phys. Oceanogr. 32, 3233–3248.2.0.CO;2>CrossRefGoogle Scholar
Avicola, G. & Huq, P. 2003 a The role of the outflow geometry in the formation of the recirculating bulge region in coastal buoyant outflows. J. Marine Res. 61, 411–434.CrossRefGoogle Scholar
Avicola, G. & Huq, P. 2003 b The characteristics of the recirculating bulge region in coastal buoyant outflows. J. Marine Res. 61, 435–463.CrossRefGoogle Scholar
Boyer, D. L., Haidvogel, D. B. & Pérenne, N. 2001 Laboratory–numerical comparisons of flow over a coastal canyon. J. Atmos. Tech. 18, 1698–1718.Google Scholar
Davies, P. A., Jacobs, P. T. G. A. & Mofor, L. A. 1993 A laboratory study of buoyant fresh water boundary currents in tidal crossflows. Oceanol. Acta 16, 489–503.Google Scholar
Griffiths, R. W. 1986 Gravity currents in rotating systems. Annu. Rev. Fluid Mech. 18, 59–89.CrossRefGoogle Scholar
Griffiths, R. W. & Hopfinger, E. J. 1983 Gravity currents moving along a lateral boundary in a rotating fluid. J. Fluid Mech. 134, 357–399.CrossRefGoogle Scholar
Hickey, B. M., Pietrafesa, L. J., Jay, D. A. & Boicourt, W. C. 1998 The Columbia River Plume Study: subtidal variability in the velocity and salinity fields. J. Geophys. Res. 103 (C5), 10339–10368.CrossRefGoogle Scholar
Horner-Devine, A. R., Fong, D. A., Monismith, S. G. & Maxworthy, T. 2006 Laboratory experiments simulating coastal river inflow. J. Fluid Mech. 555, 203–232.CrossRefGoogle Scholar
Lentz, S. J. & Helfrich, K. R. 2002 Buoyant gravity currents along a sloping bottom in a rotating fluid. J. Fluid Mech. 464, 251–278.CrossRefGoogle Scholar
Rivas, D., Velasco Fuentes, O. U. & Ochoa, J. 2005 Topographic effects on the dynamics of gravity currents in a rotating system. Dyn. Atmos. Oceans 39, 227–249.CrossRefGoogle Scholar
Rottman, J. W. & Simpson, J. E. 1983 Gravity currents produced by instantaneous releases of a heavy fluid in a rectangular channel. J. Fluid Mech. 135, 95–110.CrossRefGoogle Scholar
Simpson, J. E. 1997 Gravity Currents in the Environment and the Laboratory, 2nd edn. Cambridge University Press.Google Scholar
Thomas, P. J. & Linden, P. F. 1998 A bi-modal structure imposed on gravity-driven boundary currents in rotating systems by effects of the bottom topography. Exp. Fluids 25, 388–391.CrossRefGoogle Scholar
Thomas, P. J. & Linden, P. F. 2007 Rotating gravity currents: small-scale and large-scale laboratory experiments and a geostrophic model. J. Fluid Mech. 578, 35–65.Google Scholar