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Laboratory and numerical experiments of gravity-driven coastal currents: comparison with a geostrophic model

Laboratory experiments and numerical simulations of buoyant, gravity-driven coastal plumes flowing along a vertical coastline are summarized and compared to the inviscid geostrophic theory of Thomas & Linden 2007*. The lengths, widths and velocities of the buoyant currents, as well as their internal structure and dynamics, are studied. Agreement between the laboratory and numerical experiments and the geostrophic theory is found to depend on two non-dimensional parameters which characterize, respectively, the steepness of the plumes’ isopycnal interface and the strength of horizontal viscous forces. The best agreement between experiments (both laboratory and numerical) and the geostrophic theory are found for the least viscous flows. For some combinations of the non-dimensional parameters, instabilities develop in the seaward edge of the buoyant plumes. The laboratory and numerical experiments are used together to infer the region within parameter space within which the instabilities occur.

*Thomas, P.J. , Linden, P.F. (2007) "Rotating Gravity Currents: Small-scale and large-scale experiments and a geostrophic model". J. Fluid Mech. 578 , 35-65