Influence of heterogeneous air entry pressure on large scale unsaturated flow in porous media

Abstract

A b s t r a c tThe paper presents numerical simulations of water infiltration in unsaturated porous media containing coarse-textured inclusions embedded in fine-textured background material. The calculations are performed using the two-phase model for water and air flow and a simplified model known as the Richards equation. It is shown that the Richards equation cannot correctly describe flow in the presence of heterogeneities. However, its performance can be improved by introducing appropriately defined effective capillary and permeability functions, representing largescale behaviour of the heterogeneous medium.

Experimental and Numerical Analysis of Air Trapping in a Porous Medium with Coarse Textured Inclusions

“…During infiltration a significant amount of air was trapped in the coarse textures inclusions, both in the form of isolated bubbles in pores and larger unsaturated regions in the upper part of each inclusions. These results are in agreement with earlier experiments (Dunn andSilliman 2003, Dunn 2005) and with theoretical and numerical analyses (Szymkiewicz et al 2012(Szymkiewicz et al , 2014). The experimental results were reproduced with numerical simulations based on a two phase flow model with fitted parameters.…”

Impact of Displacement Direction Relative to Heterogeneity on Averaged Capillary Pressure‐Saturation Curves

“…Lenses, or blocks, with higher or lower permeabilities compared to the background permeability were generally considered as the micro‐heterogeneity in these studies. These studies concluded that the presence of micro‐heterogeneity can significantly change the P c ‐ S w curves (An, Erfani, et al., 2020; An, Hasan, et al., 2020; Ataie‐Ashtiani et al., 2001, 2002; Das et al., 2004, 2006; Eichel et al., 2005; Ferrand & Celia, 1992; Mirzaei & Das, 2007; Szymkiewicz et al., 2012, 2014). For instance, due to the presence of lower permeability lenses in a higher permeability porous medium, the trend of the capillary pressure curve was different from the corresponding capillary pressure curve of the high permeability background.…”

Simulations of air and water flow in a model dike during overflow experiments

“…The air remaining in inclusions cannot escape unless its pressure exceeds the entry pressure of the background material. As a result, local unsaturated zones are formed, with continuous air phase in the pores of coarse inclusion [11,36,40,42].…”