Compressibility control on gas-liquid-grain displacement dynamics

This study probes how gas compression governs the morphodynamics of gas-liquid-grain displacement in confined granular systems, a process vital to many applications like air sparging and carbon sequestration. Combining experiments and theory, we find that facilitating compression yields effects analogous to decreasing the classic capillary number. This analogy arises from the diminished transient flow rates due to the underlying coupling between viscous liquid displacement and gas pressure buildup. A theoretical model is developed to resolve this coupling, accurately matching the reduced injection pressure and prolonged breakthrough time observed in experiments. We further introduce a compression-dependent capillary number Ca_C that effectively captures the pattern transitions. Our findings underscore the role of compressibility in gas-driven flows—typically neglected in laboratories yet becoming increasingly critical toward industrial relevance. © 2026 authors. Published by the American Physical Society.