A Continuum Theory of Nonequilibrium Two-Phase Flow through Porous Media with Capillary Relaxation

摘要

Capillary relaxation is an important effect that must be properly characterized in modeling subsurface flow and transport processes. Here we present a continuum theory of porous media that accounts for the effects of capillary relaxation. A new procedure is proposed to determine relaxation times based on the acoustical technique. By virtue of the notion of linear viscoelasticity, a new model is developed to take into account the hereditary effects of capillarity. Numerical examples are presented to illustrate the time-dependent effects of the soil moisture characteristics (SMC). It is shown that increase in the rate of matric suction shifts upward the drying SMC curve and that this effect diminishes with decrease in the capillary relaxation time. Numerical results are consistent with experimental observations, implying that the proposed theory can be used to simulate the nonequilibrium flow in unsaturated soils.