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Interfacial Mixing of Dense-Water Overflow in a Converging and Upsloping Channel

Author(s): Janek Laanearu; Alan J S Cuthbertson; Peter A Davies

Linked Author(s): Janek Laanearu

Keywords: No Keywords

Abstract: Purpose of the study is to explain experimental results of dense bottom currents in the upward-sloping, converging triangular channel. High-resolution velocity and density profiles are used to analyze the changes of interface shape and mixing process for different salt-water inflow rates and bottom slopes. The stratified flow dynamics of the convectively accelerating dense water overflow is determined with an upward cascading process of energy toward the upper fresh-water layer. The internal-flow structure reveals different interfacial processes for two bottom slope cases (denoted as Weir and Sill). In the case of relatively steep up-sloping converging-channel and horizontal exit-channel (Weir) sections, the deep-water motion has sub-critical conditions throughout and is characterized by a comparatively sharp density interface and relatively small deep-water velocities. In the case of relatively mild up-sloping channel and highest bottom point (Sill) between converging-channel and exit-channel sections, the internal motion is determined by relatively large deep-water velocities and diffused density interface near to the2sill2section. The density and velocity interfaces are vertically diverged in the case of combined Froude number sq G 2 →1. The density-profile gradient minimum in the Weir case is determined by the density excessr’~0. 5 and in the Sill case byr’~0. 3 for the flow rates considered. The internal-energy function is used to determine the internal-head losses due to bottom friction. The gradient Richardson number profiles are calculated to characterize the stationary turbulent process in the topographically constrained and stratified flow cases. The relationship between the interfacial Reynolds stresses and the net-entrainment process is discussed.


Year: 2012

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