Editorial: Nonequilibrium multiphase and reactive flows in porous and granular materials

Porous systems that involve the flow of multiple fluids, particles, or solutes, capable of undergoing reactions with each other or with the solid porous matrix, often exist in an out-of-equilibrium state. These systems are driven away from equilibrium by various underlying mechanisms. These mechanisms include interfacial instabilities caused by capillary or viscous forces, as well as physical alteration of the pore space through mechanical or chemical processes like fracturing, compaction, precipitation, and dissolution. An inherent feature of many porous and granular systems is their multiscale heterogeneity. An extreme example is in geosciences, where heterogeneity and mechanisms at the microscopic scales (e.g., in nanometer-sized pores) could strongly affect the behavior at the field scale (km-sized reservoirs). The multiscale, nonequilibrium nature of these systems is manifested by the emergence of complex, preferential flow patterns and dependencies on the path (hysteresis) and rate of external driving forces. Modeling, understanding, predicting, and even controlling the evolution of the flow and deformation in these systems is a substantial scientific challenge across disciplines including engineering, physics, geosciences and mathematics and plays a crucial role in multiple practical applications.