Comparison of the single-phase and two-phase numerical model formulation for saturated-unsaturated groundwater flow (Q1094993)

Two numerical methods are developed for transient saturated-unsaturated two-dimensional groundwater flow. One formulation uses the usual single- phase formulation with a passive air phase at constant pressure. The second model uses a full two-phase air-water formulation. The numerical results for both formulations are compared on some test problems. In some cases, the single-phase formulation and the two-phase formulations give greatly different results. This can be explained in terms of the fractional flow curve for the air-water system. The single-phase technique generally requires less computational work than the two-phase formulation, although there are some situations where the numerical performance of the single-phase formulation is very poor.