Gravity Fingering During Water Infiltration in Soil: Potential Implications for the Ecohydrology of Arid Climates

The displacement of one fluid by another in a porous medium gives rise to a rich variety of hydrodynamic instabilities. Beyond their scientific value as fascinating models of pattern formation, unstable porous-media flows are essential to understanding many natural and man-made processes, including water infiltration in the vadose zone, carbon dioxide injection and storage in deep saline aquifers, and methane venting from organic-rich sediments. Here, we review the gravity-fingering instability that emerges during water infiltration in soil, and propose a phase-field modeling framework that captures the phenomenon and permits quantitative predictions.