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Obtaining a Semi-analytical Solution for Contaminant Transport in Coastal Aquifers: Fourier-galerkin Method

Koohbor, Behshad | 2017

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 49613 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Ataie-Ashtiani, Behzad; Jamali, Mirmosaddegh
  7. Abstract:
  8. Existing closed form solutions of contaminant transport problems are limited by the mathematically convenient assumption of uniform flow. These solutions cannot be applied for coastal aquifers where seawater intrusion induces a variable velocity field. The Fourier series method is adapted to obtain a semi-analytical solution for contaminant transport in confined coastal aquifer in which the saltwater wedge is in equilibrium with a freshwater discharge flow. The developed method can be applied for different scenarios of contamination. Two scenarios dealing with, respectively, contaminant leakage from a source at the aquifer top surface and aquifer contamination from the landward boundary are discussed in this paper. The results show that the method developed here associates the exactness of the analytical solutions to an important extent of flexibility in addressing realistic configurations. Verification test cases and comparison against numerical solutions highlight the accuracy and the robustness of the semi-analytical solution. The Fourier series are used to evaluate relevant metrics characterizing contaminant transport such as the discharge flux to the sea, the amount of contaminant persisting in the groundwater and the solute flux as measured by the Sherwood number. The semi-analytical method is used to understand the effect of seawater intrusion on these metrics. For the first scenario, seawater intrusion limits the spread of the contaminant but leads to more contaminant discharge to the sea. For the second scenario, moderate seawater intrusion affects only the spatial distribution of the contaminant plume. Extreme seawater intrusion can increase the contaminant discharge to the sea
  9. Keywords:
  10. Coastal Aquifer ; Sea Water Intrusion ; Semi-Analytical Solution ; Numerical Method ; Contaminants Transport ; Fourier-Galerkin Method

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