A Three-Dimensional Finite Element - Finite Difference Model for Simulating Confined and Unconfined Groundwater Flow

Abstract

Publisher Summary This chapter discusses finite difference model for simulating confined and unconfined ground-water flow. Numerical models for the simulation of ground-water flow and contaminant transport are well-established. It is clear that accurate simulation of many contaminant transport problems requires a three-dimensional ground-water flow solution. Some three-dimensional ground-water flow models have been developed and tested. Application of these models often has been constrained by core storage and central processing unit (CPU) time requirements, especially, for unconfined flow problems. Elements that become completely drained by pumping—or conversely, previously drained elements that become refilled by recharge-can cause numerical difficulties. A procedure was introduced that not only effectively removes the influence of the drained element and the associated nodes, but also allows for refilling. The procedure consists of imposing Dirichlet conditions on the associated drained nodes, equal to the head from the layer immediately below. If a source or a sink term exists at a drained node, the location of the source or sink is temporarily removed from the drained node and the quantity of the source or sink is allocated to the remaining layers below.