Finding preferential paths by numerical simulations of reactive non-darcy flow through porous media with the Lattice Boltzmann method

Preferential flow is still an elusive phenomenon in porous media, impacting the oil industry, micro- and nanofluidic applications, and soil sciences. The Lattice Boltzmann Method (LBM) with the Pore-Scale approach is a robust mesoscopic tool for modeling flows in complex geometries, detailing velocity fields, and identifying preferred pathways. Since preferential flow has several causes, it is hard to distinguish and evaluate the different contributions to the phenomenon. However, a starting simplification assumes that geometrical features are its primary cause. In this work, we discuss some insights about preferential flow and verify the validity of a previous tortuosity-dependent resistance model in a non-Darcy regime. Initially, we demonstrate that the Pore-Scale LBM recovers the Forchheimer empirical model. Although the tortuosity model reasonably predicts many preferred pathways, the inertial contributions in the Forchheimer regime make the porous pattern, grain shape, and path deflections disturb those predictions. The simulations indicate that paths with minor flow resistances affect the neighboring flow preferences. Dead zones arise by imposing clogging conditions, and the flow field and preferred paths change. Wondering how the observed preferential routes impact the evolution of a reactive flow, a mass transport analysis was carried out to track the porosity evolution during the reactive dissolution of the solid structures. As a result, the matrix porosity increases over time, especially under diffusion- and kinetic-dominated conditions.