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Development of an integrated free surface and groundwater flow model

Ebrahimi, Kumars 2004. Development of an integrated free surface and groundwater flow model. PhD Thesis, Cardiff University.

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Keywords: Numerical Modelling, 2-D Free Surface/Groundwater flow modelling, Solute Transport, Physical Modelling, Dye Tracer An integrated novel, two-dimensional, numerical groundwater-surface flow model has been developed to simulate hydro-environmental interactions between wetland areas, the neighbouring coastal waters and the groundwater passages. The main target in this research was to prepare a general linked model, which could be applied to different applications. For free surface flow modelling, an existing widely used two-dimensional, unsteady mathematical model, named the DIVAST model (Depth Integrated Velocities And Solute Transport model, developed originally by Falconer 1976) has been refined. However, in order to simulate the flow and solute transport in porous media, a two-dimensional model namely the GWK (Ground Water Key) has been developed to include an aquifer influenced by tidal currents. The GWK model is based on the transient flow Boussinesq equation as the governing equation for groundwater flow, and the advection-diffusion equation is used as the governing equation for contaminant transport. The model predicts the water table, the velocity components in the horizontal plane, the recharge/discharge levels for source/sink on the water table and solute tracer levels across the domain. The finite difference scheme used in this model is based upon the Alternating Direction Implicit (ADI) technique and using orthogonal grids. The structure of the GWK model is based on having a good relationship with the free surface flow model. The two sub-models (DIVAST-GWK) are linked by an interface, and flow and pollutants are able to pass across the interface in both directions, depending on the relative height of the water levels. A physical scale model has been constructed to provide experimental data of the groundwater transport between an idealised wetland and the adjacent coastal waters. However, in the dimensional analysis and designing of the physical model the Fleet Lagoon and adjacent coastal waters, in Dorset just west of Weymouth and the Isle of Portland UK, was chosen as a typical prototype. In the physical model the aim has been to study seepage behavior through the sand embankment by recording water levels on both sides of the sand, point velocity measurements, and the studies of a conservative dye tracer for constant water levels on one side of the embankment while running tidal cycle on the other side of the sand ridge. The integrated model has been verified using the laboratory data. Comparison between the experimental data and the simulated physical model, involving numerical linked model, showed that the integrated model was capable of simulating both phenomena, groundwater and free surface water, with a high level of accuracy.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Engineering
ISBN: 9781303200083
Date of First Compliant Deposit: 30 March 2016
Last Modified: 10 Oct 2017 15:28

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