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The Effects of a Time-Varying Source upon the Motion of a Continuous Saline Underflow

Author(s): Rocio Luz Fernandez; Jorg Imberger

Linked Author(s): Jörg Imberger

Keywords: Unsteady; Underflow; Buoyancy; Front velocity

Abstract: This paper describes a laboratory investigation of a continuous discharge gravity current moving down an inclined plane into a stratified ambient fluid; the source density decreasing linearly with time, initially larger and finally smaller than the bottom ambient density. The experimental observations show that the inflowing water propagates with both underflowing and intrusive flow regimes. Hence, at earlier times of the experiment the underflow was observed to descend attached to the sloping bottom with a speed that was consistent with that given by the theory for a buoyancy-conserving gravity current on gentle slopes. However, as the density of the inflow reduced with time, the front of the underflow decelerated and its body was observed to split into an upper intrusion along the incline. Notably, these laboratory observations show that, even where the fluid input is continuous, non-particulate underflows may propagate with a decelerating front; this dynamics somewhat akin to the motion of a fixed volume which is being feeding from behind by the unsteady continuous source. To the end of the experiment, multiple intrusions were established successively at different depths in between the initial underflow and the surface buoyant plume.


Year: 2007

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