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UBC Theses and Dissertations

Characteristics of tidally-forced pollutant transport in narrow channels Cole, Michael J. B.


Physical and numerical model studies have been conducted to lend insight to the subject of transport and dispersion of a neutrally buoyant effluent released instantaneously from a point source into a one-dimensional tidal body. Closedform expressions are obtained for the fluid velocity and free surface elevation due to tidal forcing in a one-dimensional channel. Physical experiments were conducted in the Hydraulics Laboratory of the Department of Civil Engineering at the University of British Columbia, and measurements of both effluent concentration and velocity along the test channel were recorded. A numerical model based on the Finite Difference Method was developed for computing the time-varying effluent concentration within the channel. The influence of grid size and time step used in the numerical model was examined. The following parameters were varied: effluent discharge location, release time within the tidal cycle, average water depth, tidal amplitude, and tidal period. The experimental measurements and numerical predictions were correlated to derive an effective one-dimensional diffusion coefficient for the numerical model. The numerical results suggest that the fluid velocity at the instant and location of pollutant release is of primary importance to the mixing of the pollutant cloud into the surrounding waters.

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