A width-averaged hydrodynamic model of two-layer tidal circulation

Abstract

Estuaries support a unique hydrodynamic system due to the fresh water flowing into a salt water sea. This leads to stratification which can significantly alter internal tidal dynamics in the estuary. A model has been developed by Winant (2010) to describe the water motions of a two-layer system in tidal basin. The aim of this thesis is provide an extension to this model by parameterizing bottom stress using a partial slip parameter and viscosity. Also level variations of the bed are taken into account in this thesis. A width-averaged model of an idealized stratified tidal basin is developed. With increased bottom stress, the velocity near the bed is significantly slowed down, whereas increasing the viscosity slows down the velocity further away from the bed. The interface fluctuates more when the viscosity is low, the wavelength of these fluctuations is decreased with increasing viscosity. Resonance characteristics in the hydrodynamics are dampened severely by increased viscosity, and less by bottom stress. Increasing the slope of the bed results in a lag of tidal dynamics at the end of the embayment compared to at the embayment entrance. A sloped bed also dampens the resonance characteristics.