Evaporation-driven density instabilities in saturated porous media

TL;DR

This paper investigates how evaporation causes density-driven instabilities in saline-saturated soils, leading to finger-like salt transport, using linear stability analysis and numerical simulations to predict their onset and development.

Contribution

It introduces a combined linear stability and numerical simulation approach to predict evaporation-induced salt fingering in saturated porous media, advancing understanding of soil salinization processes.

Findings

Criteria for instability onset across parameter ranges

Simulation results on finger development after onset

Predictions of salt concentration evolution near the surface

Abstract

Soil salinization is a major cause of soil degradation and hampers plant growth. For soils saturated with saline water, the evaporation of water induces accumulation of salt near the top of the soil. The remaining liquid gets an increasingly larger density due to the accumulation of salt, giving a gravitationally unstable situation, where instabilities in the form of fingers can form. These fingers can hence lead to a net downwards transport of salt. We here investigate the appearance of these fingers through a linear stability analysis and through numerical simulations. The linear stability analysis gives criteria for onset of instabilities for a large range of parameters. Simulations using a set of parameters give information also about the development of the fingers after onset. With this knowledge we can predict whether and when the instabilities occur, and their effect on the salt concentration development near the top boundary.