Modeling displacement properties of immiscible fluids in porous media

Fluid transport through porous structures is a subject of active research, both theoretically and experimentally. In this article, the authors provide a modified model of flow that gives a detailed description of fluid penetration through hydrophobic, nonwoven networks. The porous medium was modeled as parallel cylindrical capillaries in two different ways: one with uniform diameters across the capillary length, referred to as the "capillary model", and a modified version with sections of different diameters across the capillary length, called the "ink-bottle model". To validate the numerical results, an experimental methodology was also developed. The methodology made use of a pressure/flow cell in which the sample was mounted. The flow rates were measured during sequences of increasing and decreasing pressures applied to the displacing nonwetting fluid (aqueous solution). The ink-bottle model reproduced all the wetting patterns that were observed in the experiments, while the capillary model was able to capture only the patterns observed during the initial contact of the fabric with the solution.