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Numerical Simulation of Ice-Cover Influence on Nearfield Mixing

Author(s): Cheng-Ann Tan; Sanjiv K. Sinha; Robert Ettema

Linked Author(s): Robert Ettema

Keywords: Computational Fluid Dynamics; Contaminant transport; Numerical Modeling; Dunes; Ice cover influence

Abstract: This paper presents the results of a numerical-simulation investigation of ice-cover influence on the mixing and transport of a neutrally buoyant contaminant released in a straight reach of a dune-bed channel. The investigation used a three-dimensional computational fluid dynamics model, validated against flume data for flow distribution in the channel and against a simple analytical solution for mixing in the channel. The model was used to simulate contaminant release near the ice-cover underside and near the bed. The results show that, for constant water discharge, cover presence reduces near-field mixing because it redistributes the flow, increases flow depth, decreases bulk velocity, reduces maximum level of turbulence, and modifies dune geometry. For the ice-covered flow, a contaminant released near the bed or near the cover underside remains closer to those boundaries over a longer distance than for openwater flow. The simulation shows that cover presence reduces the depth-averaged diffusivity to about 45% of the corresponding diffusivity for openwater flow. The distance to attain full mixing across the flow depth increases by a commensurate amount.

DOI:

Year: 1999

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