Boundary element simulation of three-dimensional saltwater intrusion problems.
Committee ChairContractor, Dinshaw N.
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PublisherThe University of Arizona.
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AbstractA numerical model for the analysis of three-dimensional flow of two immiscible fluids through porous media is developed based on the boundary integral equation technique. Hydrodynamic dispersion is assumed to be negligible and therefore a sharp interface is assumed to separate the two fluids. Triangular elements are used to discretize the boundary of the solution domain and the areal integration over triangles is reduced to a linear form by carrying out analytical integration along one coordinate direction. As a result,the singular integrals are reduced to completely analytic forms, thus avoiding the need of using a large number of Gauss points for numerical integration as used in some earlier models. This is found to result in substantial saving in computer time and increased accuracy of results, even at points close to the boundary. The model is verified by comparing its results to those from analytic solutions and other numerical methods like the Finite Element Method. An efficient two-dimensional Finite Element Model is also developed to simulate salt water intrusion. Both the Boundary Element Model and the Finite Element Model are applied to the problem of sea water intrusion in the coastal aquifer of Guam and the results are discussed. It is observed that the boundary element method, in general, requires smaller time steps as compared to the finite element method in order to get stable results for transient flow problems. The increase in number of time steps, however, is compensated by the smaller number of nodes and the overall computational effort appears to be of the same order for both the methods.
Degree ProgramCivil Engineering and Engineering Mechanics