Two‐phase flow infiltration equations accounting for air entrapment effects

Abstract

Abstract. Water infiltration into the unsaturated zone is potentially affected by air compression ahead of the wetting front. Analytical infiltration equations accounting for air compression, air counterflow, and flow hysteresis in a porous medium were derived on the basis of the Green and Ampt [1911] assumptions. Air compression ahead of the wetting front was predicted using the perfect gas law. The capillary pressure at the wetting front was found to vary between the dynamic water-bubbling value and the dynamic airbubbling value of the material. These equations, accounting also for the effects of macropores near the soil surface, turned out to be simpler than the traditional Kostiakov Their studies were mostly based on the assumption that the air displaced by the infiltrating water escapes so readily that the pressure of the soil air is atmospheric [Philip, 1957c] The objectives of this study are (1) to present a simple set of a two-phased Green and Ampt [1911] model accounting for air compression and dynamic change of capillary pressure at the wetting front, (2) to derive a set of analytical infiltration equations accounting for air compression, air pressure fluctuation/air eruption, flow hysteresis, and macropores in a porous 2759

Infiltration into soils: Conceptual approaches and solutions

“…Therefore, all the solutions of the flow equation presented here earlier, which assume that air can move freely within the porous medium and remain practically at atmospheric pressure so that its impact on the movement of water can be neglected, can be applied. However, under conditions of flood irrigation, intense rainfall, and soil column experiments, air can be compressed at the wetting front and beyond and reduce significantly the infiltration rate until it could find a way to escape and release that pressure buildup [Peck, 1965;McWhorter, 1971;Dixon and Linden, 1972;Vachaud et al, 1974;Touma et al, 1984;Wang et al, 1998]. Solving the problem of two-phase flow in porous medium presented an increased interest since oil can replace air in the two-phase definition and thus address practical issues related to the oil industry.…”

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