Abstract:
Evaluation of the hysteretic drainage and wetting phenomena exhibited by porous media is relevant to many branches of science and engineering. In subsurface hydrology, these processes play a particularly important role in the vadose zone where the soil is partially saturated with water. In this paper, we focus on the determination of the water retention curve for a porous medium through a novel pore-scale simulation technique that is based on mathematical morphology. Advances in tools for analyzing 2- and 3-D images have made this technique very attractive for elucidating macroscopic relationship from pore-scale analysis. We present an algorithm that allows for the representation of three-dimensional randomly packed porous media of any geometry (i.e. not restricted to idealized geometries such as spherical or ellipsoidal particles/pore space) so that the connectivity-, tortuosity-, and hysteresis-causing mechanisms are represented properly, and their role in determining macroscopic fluid behavior is made explicit. Using this method, we present simulation results that include both drainage and wetting processes, in order to demonstrate hysteretic effects. Entrapment of wetting and non-wetting phases during both drainage and wetting are also represented explicitly. This technique is used to model hysteresis behavior and the relationships between water pressure, saturation and interfacial area. Strengths and limitations of this method are described.
