The influence of airflow on the vertical infiltration of water into soil
1992
Weir, G.J. | Kissling, W.M.
The vertical flow of air and water into a Gardner soil is investigated numerically and analytically. Instantaneously applying a constant head of water to the soil surface initially produces a rapid diffusive change in air pressure in the soil, and a slower diffusive change in water content. Fluid flow comprises a region of descending water at air entry conditions, below which is a transitional layer of both airflow and water flow, which connects to a region with essentially the initial value of capillary pressure. Four flow regimes are identified. The initial compressive and resistive regimes are associated with air compressibility and viscosity. The well-known sorptive and gravity regimes are established later. During the resistive regime, the main effect of air viscosity arises from airflows in the lower region which cause the water content profile to lag behind the corresponding profiles predicted without effects of air viscosity. A Green and Ampt infiltration law may accurately describe the infiltration process, provided the suction head suggested by Bouwer is selected. Approximate agreement is obtained between the theoretical predictions, and the corresponding accurate numerical results.
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