Dynamic of Air Invasion in an Immersed Granular Layer

Displacement processes (typically, grains displaced by a fluid) are the driving mechanism which control the dynamics of many geological processes (e.g. oil extraction, air sparging, piercement structures). They also play an important role in a wide range of industrial applications, from ground water hydrology and soil mechanics to agricultural engineering. The interaction between one or more moving fluids (e.g. rising gas immersed in a granular medium) and grains control the dynamics of these phenomena. Due to their economic and ecological importance, it is essential to understand the variety and potentiality of these phenomena. When an ascending air passes trough an immersed granular bed its fluidized producing the grains to start to move. When this process is repeated, its created a fluidized zone that evolves over time. Here, we investigate the morphology and dynamics of the region invaded by air as a function of a dimensionless parameter χ which accounts for the relative effects of the gravity and the capillarity. We propose new experimental observations on the air invasion regimes and on the morphology of the fluidized zone, in particular its growth dynamics.