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

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Thomas, P. J. (Peter J.) and Linden, P. F.. (2010) Laboratory modelling of the effects of temporal changes of estuarine-fresh-water discharge rates on the propagation speed of oceanographic coastal currents. Journal of Fluid Mechanics, Vol.664 . pp. 337-347. ISSN 0022-1120

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Official URL: http://dx.doi.org/10.1017/S0022112010004702

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.

Item Type:	Journal Article
Subjects:	T Technology > TA Engineering (General). Civil engineering (General) T Technology > TC Hydraulic engineering. Ocean engineering
Divisions:	Faculty of Science > Engineering
Library of Congress Subject Headings (LCSH):	Ocean currents, Estuarine hydrology
Journal or Publication Title:	Journal of Fluid Mechanics
Publisher:	Cambridge University Press
ISSN:	0022-1120
Date:	December 2010
Volume:	Vol.664
Number of Pages:	11
Page Range:	pp. 337-347
Identification Number:	10.1017/S0022112010004702
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
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. Avicola, G. & Huq, P. 2003a The role of the outflow geometry in the formation of the recirculating bulge region in coastal buoyant outflows. J. Marine Res. 61, 411–434. Avicola, G. & Huq, P. 2003b The characteristics of the recirculating bulge region in coastal buoyant outflows. J. Marine Res. 61, 435–463. Boyer, D. L., Haidvogel, D. B. & P´erenne, N. 2001 Laboratory–numerical comparisons of flow over a coastal canyon. J. Atmos. Tech. 18, 1698–1718. 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. Griffiths, R. W. 1986 Gravity currents in rotating systems. Annu. Rev. Fluid Mech. 18, 59–89. Griffiths, R. W. & Hopfinger, E. J. 1983 Gravity currents moving along a lateral boundary in a rotating fluid. J. Fluid Mech. 134, 357–399. 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. 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. Lentz, S. J. & Helfrich, K. R. 2002 Buoyant gravity currents along a sloping bottom in a rotating fluid. J. Fluid Mech. 464, 251–278. 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. 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. Simpson, J. E. 1997 Gravity Currents in the Environment and the Laboratory, 2nd edn. Cambridge University Press. 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. 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.
URI:	http://wrap.warwick.ac.uk/id/eprint/41662