| Summary: | The simulation of groundwater contamination by nonaqueous phase liquids (NAPLs), such as organic solvents and petroleum hydrocarbons, requires a solution of the multiphase flow, heat flow and pollutant transport through soil. Also, the contaminant can exist within the gas and water phases. A multi-phase flow model, based on the two-phase flow model of Brooks and Corey, that expresses the dependence of saturation and relative permeability on capillary pressure is presented. The nonlinear behaviour of the saturation versus relative permeability functions is incorporated into a Galerkin finite element model that is used to simulate the vertical infiltration of immiscible/miscible fluid in unsaturated and saturated porous media. The governing partial differential equations, in terms of soil displacements, fluid pressures, energy balance and concentrations are coupled and behave non-linearly but can be solved by the finite element method. In order to apply the finite element model to a specific problem a number of parameters must be evaluated. These include relative permeabilities, saturation-pressure relations, mass transfer coefficients and densities. Numerical implementation of the formulation is discussed, and example problems are presented for verification. As a demonstration of the model's applicability, the migration of a contaminant is simulated in 1D and 2D problems. Also, an approximate numerical solution to the theoretical model is presented. The weighted residual finite element approach is employed to achieve spatial discretisation of the problem while temporal discretisation is achieved by a fully implicit scheme. A verification and validation programme has been implemented to assess the integrity of the theory, discretisation approach and the code itself. Several exercises verifying the consolidation model are presented. Validation exercises for the cases of isothermal, non-isothermal, saturated and unsaturated conditions of the coupled flow of heat, water and gas in a deforming porous medium, are performed. Finally, the fully coupled model is verified by comparison with results from an alternative model.
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