Dynamic capillary pressure during water infiltration: Experiments and Green‐Ampt modeling

Abstract

[1] In a recent study by Hsu and Hilpert (2011), the Green-Ampt (GA) model for water infiltration was modified to account for a dynamic capillary pressure that depends on the wetting front velocity. In that study, the only transient flow, to which the modified GA approach was compared, was capillary rise. In this paper, transient downward infiltration experiments were performed using three different ponding depths. We demonstrated that infiltration can be effectively modeled using the modified GA approach. The parameters of the dynamic capillary pressure relationship were fitted and independent of the ponding depth. Furthermore, the experimental data could not be described accurately at early times with the classical GA approach. This was particularly evident when plotting the product between the Darcy velocity and the wetting front position against the wetting front position. In these plots, the initial unphysical infinite rate of infiltration, that occurs in the classical GA model, appears to be a primary element of inaccuracy. It was furthermore verified that the limited ability of the classical GA approach to describe the experimental data is not related to inertial forces arising during the initial phase of infiltration.

The role of contact angle on unstable flow formation during infiltration and drainage in wettable porous media

“…A shift factor to that correlation is associated with the static contact angle [ Hoffman , ]. Hilpert and co‐authors [ Hilpert , ; Hsu and Hilpert , ; Pellichero et al ., ] found that the dynamic contact angle affects the flow in uniform capillary tubes and the analogous Green and Ampt model [ Green and Ampt , ] used to simulate infiltration in soils. Weitz et al .…”

Infiltration and evaporation of small hydrocarbon spills at gas stations

“…As shown in Figure 7a, almost one half of the gasoline infiltrates into the concrete despite its very low permeability. This can be attributed to the capillary action which gives rise to a huge driving force during the initial phase of infiltration (Washburn, 1921;Hilpert, 2009;Hsu and Hilpert, 2011;Pellichero et al, 2012). Since the total droplet volume is so small, the late and slow phase of infiltration is not reached.…”

Effects of the Grain Size on Dynamic Capillary Pressure and the Modified Green–Ampt Model for Infiltration

“…The best β value was approximately 0.31 for the experiments performed by Geiger and Durnford [25]. Pellichero et al [26] showed that β = 0 3 resulted in the best fit in downward infiltration experiments with the same sand but varying ponding heights. The same β value also worked well in similar experiments but with various initial water contents [11].…”

“…This dynamic component depends on both flow dynamics and the process of either drainage or imbibition. In addition, studies conducting column experiments have shown that during downward infiltration, the water pressure head at the gas-water or liquid-liquid interfaces changes as the flow velocity changes [11,[23][24][25][26][27][28]. The aforementioned studies suggest that the capillary pressure under dynamic conditions can be less than that under static conditions during infiltration.…”

“…Hsu et al and Pellichero et al [11,26] showed that the MGAM approach can avoid the initial unphysical infinite rate of infiltration and better describe the experimental results than can the classical GAM for downward infiltration at an early stage in both dry and prewetted sand columns with varied initial water contents. Indications are that the grain size and pore size distributions affect the dynamic effect on the soil water retention curve [20,[35][36][37].…”