MODELING FLUID-FLOW AND TRANSPORT IN VARIABLY SATURATED POROUS-MEDIA WITH THE STOMP SIMULATOR .2. VERIFICATION AND VALIDATION EXERCISES

STOMP, a subsurface flow and transport simulator for investigating remediation technologies, described in the preceding paper, is tested against simulation results from a published numerical code, MOFAT-2D, and against nonhysteretic and hysteretic data from three-phase flow experiments. There is good agreement between the STOMP and MOFAT-2D simulations and between measured data and numerical results when STOMP is used to simulate the experiments. However, there are some discrepancies between measured and predicted fliud contents. Discrepancies at low fluid contents are assumed to be a function of relative permeability-saturation relations, and discrepancies near complete wetting-fluid saturation are assumed to be caused by failing to account for a nonwetting-fluid entry pressure in the fluid saturation-pressure relations. Despite the discrepancies, overall predictions of subsurface fluid behavior are good. These results suggest that STOMP may accurately forecast multiphase-flow behavior at a site when the site is adequately characterized and the model parameters are correctly calibrated to the site.