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

Szymańska P., Tisler W., Schütz C., Szymkiewicz A., Neuweiler I., Helmig R.

Acta Geophysica

2016

Vol. 64, no. 6

2487--2509

The paper presents a 2D upward infiltration experiment performed on a model porous medium consisting of fine sand background with two inclusions made of coarser sands. The purpose of the experiment was to investigate the effects of structural air trapping, which occurs during infiltration as a result of heterogeneous material structure. The experiment shows that a significant amount of air becomes trapped in each of the inclusions. Numerical simulations were carried out using the two-phase water-air flow model and the Richards equation. The experimental results can be reproduced with good accuracy only using a two-phase flow model, which accounts for both structural and pore-scale trapping. On the other hand, the Richards equation was not able to represent the structural trapping caused by material heterogeneity.

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

Szymkiewicz A., Neuweiler I., Helmig R.

Acta Geophysica

2014

Vol. 62, no. 5

1179--1191

The 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. How-ever, its performance can be improved by introducing appropriately de-fined effective capillary and permeability functions, representing large-scale behaviour of the heterogeneous medium.