Multiscale pore network construction for two phase flow simulations in granular soils

Abstract

Characterizing and modeling the pore structure is the key to simulating single and multiphase flow through granular soils. Modeling the grain-based packing and predicting the multiphase flow properties of granular soils with a wide grain size distribution (GSD) spanning over several orders of magnitude is still a challenging task. This work presents a novel numerical framework for constructing the pore network of granular soils with a wide grain size variation. The present work focuses on using basic properties of granular soils like GSD and porosity to generate pore network properties that are further utilized to simulate the water retention properties of granular soils along drying and wetting paths. A topologically equivalent network of pores and throats is extracted from modeled soil packing at different length scales. By integrating the pore networks extracted from individual length scales in the main simulating domain, a multiscale pore network that represents the pore structure of the soil to be modeled is obtained. The pore-scale phenomena like piston-like advance, corner flow (wetting layers), pore body filling, and snap-off are used to model fluid displacements at the pore scale. The estimated soil water retention curves for various granular soils are in good agreement with experimental data from the literature, and the hysteretic wetting-drying response is also accurately predicted.