A Comparison of Three Methods for Solving Flow Equations of Two Immiscible Fluids in Variably Saturated Media

Three alternate methods are compared for numerically solving the coupled flow equations for two immiscible fluids in variably saturated media. The three alternate methods are (1) the Picard method, (2) the logmean method, and (3) a modified Picard method. All three methods were used to simulate an experiment with transmission oil infiltrating sand. Different time-step sizes were used for each method, and mass-balance accuracy is compared for each time-step size and method at various time values during the transient infiltration. Also, simulated contours of oil mass, using the modified Picard method, are compared to the experimental contours.