Hydrodynamic and dispersion studies in an estuary physical model incorporated with an idealized groundwater

A study on hydrodynamic and dispersion has been undertaken in an estuary physical model. The model represented the Severn Estuary in the UK which has the second largest tidal range in the world. The scale of the model was 1:125 vertically and 1:25,000 horizontally. Experiments in nine sample points showed that water level was different in those points. Velocity measurements showed that the velocity in the physical model coild be analysed using the wave resonance theory. The velocity profile measurements showed that the balance between ebb and flood tide, and this balance were different in different sampling points. The experiments were then compared to the computer modelling results. The water level model showed accordance with the experimental results. The velocity model results were then calibrated using several parameters, namely n-Manning, COED, and momentum correctioncoefficient (β). The calibration was then continued by the refinement of boundary condition and bathymetry. Studies on dispersion in the estuary physical model revealed that longitudinal dispersion coefficient affected the dispersion significantly, while the lateral turbulent diffusion affected the dispersion less significantly. Constant dispersion coefficient was compared with the variable dispersion coefficient, and the results showed that the constant dispersion coefficient gave a better representation of the dispersion process. Studies were also undertaken in an idealized groundwater which was linked to the estuary physical model. The static and dynamic conditions of the groundwater were studied. For static condition which was also undertaken to calibrate the water level probes, the change of water level in the groundwater clearly followed the changes in the estuary water levels, with a delay of water level according to the distance between the borehole and the estuary boundary. Dynamic condition of the groundwater as a results of tide in the estuary clearly shows the phase difference and the tide range at each borehole according to their distance to the estuary boundary. The effect between pump and tide was studied, and this showed clearly the effects of each component on groundwater level. Through Darcy’s analysis it was proved that the groundwater hydrodynamics follow the Darcy’s principle. Finally the dispersion in the groundwater were studied using two scenarios, namely open-open boundary and close-open boundary. Analysis results showed that open-open boundary gave lower dispersion coefficient than the close-open boundary.