Numerical Simulation of Solute Transport in Randomly Heterogeneous Porous Media: Motivation, Model Development, and Application

Abstract

A particle tracking, or "random walk" solute transport model is developed to study detailed contaminant movements through large, synthetic heterogeneous flow systems in porous media. Such simulations can be used to examine the large time and spatial effects of the variable flow field on the expanding solute plumes. More specifically, the large scale experimental dispersive behavior can be compared with theoretical predictions based upon stochastic analyses. The particle tracking model is developed from first principles and is shown to be the most computationally efficient model for this type of application. Computational issues regarding the model's implementation are discussed, including the choice of time steps, boundary and initial conditions, and conversion of solutions to concentration fields. The model is applied to some simple test problems and then to two large, three-dimensional, heterogeneous, saturated flow systems. The results of these preliminary investigations are analyzed and compared with results of stochastic theories. They are also used to plan more comprensive simulations to be carried out in the future.