Linear Finite-Element Modeling of Contaminant Transport in Ground Water

Abstract

Finite element methods (FEMs) that use piecewise linear basis functions (PLBFs) are gaining popularity over finite difference techniques in modeling contaminant transport in ground water. However, utilization of the PLBFs may lead to oscillatory results when the semidiscrete Galerkin FEM (SDGFEM) is used. The efforts directed toward eliminating oscillations in the model prediction by the SDGFEM have resulted in the introduction of the Characteristic-Galerkin FEM (CGFEM and the Petrov-Galerkin FEM (PGFEM). The objective of this paper is to investigate the stability and relative accuracy of these methods for one dimensional (1D) contaminant transport in ground water. The stability and the relative accuracy were examined for both uniform and nonuniform flow fields for a wide range of dispersion: 0.00 – 185.8 cm²/day. Transport from both continuous and pulse sources was simulated. All the methods were found to be stable. The CGFEM and the SDGFEM were found to predict the contaminant transport in ground water better than the PGFEM.