Suitability of body force model for pressure-difference driven flow in porous media

Abstract

Pore-scale direct numerical simulation is an important tool for studying the flow of porous media nowadays. This work validates the suitability of body force model for simulating pressure-difference-driven porous flows in pore-scale simulations. The multi-relaxation time lattice Boltzmann method (MRT-LBM) with the color-gradient continuum-surface-force (CG-CSF) model is employed to calculate the absolute and relative permeability of randomly generated porous media. Results show that for single-phase flows, the relative errors are below 5% for most homogeneous porous structures while as high as 80% for structures with preferential paths. This study also reveals the pore-scale flow mechanisms and proposes a new heterogeneity parameter quantified by the standard deviation of the pressure at the boundary. For multiphase flows, errors of the body force model are significant at low Ca due to irreversible phase distribution difference appearing at the early stages. The findings of this work could be applied to other transport processes in porous media. It is crucial to consider the structural heterogeneity and proper parameters when employing the body force model in pore-scale simulations.