DEM Modeling of Coupled Multiphase Flow and Granular Mechanics: Wettability Control on Fracture Patterns

The interplay between multiphase flow in a granular medium and the displacement of the grain particles generates a wide range of patterns. The balance between frictional, viscous, and capillary forces has been studied in experiments and simulations, and has helped understanding the underlying mechanisms for a wide range of phenomena, such as methane migration in lake sediments. Here we study fluid-induced fracturing of granular media by hydromechanically coupling a moving capacitor dynamic network model with discrete element modeling. We inject a less viscous fluid into a frictional granular pack initially saturated with a more viscous, immiscible fluid under low capillary number. We study the impact of contact angle and initial packing density, and find four different regimes of the fluid invasion morphology: cavity expansion and fracturing, frictional fingers, capillary invasion, and capillary compaction. We rationalize these simulation outputs by means of a jamming analysis, which allows us to explain fracture initiation as emerging from a jamming transition. We synthesize the analysis in the form of a novel phase diagram of jamming for wet granular media.