A Dual-Continuum Approach for Precipitated Salt in Porous Media: Accounting for Coupled Transport Processes

Abstract

Salt precipitation in porous media can negatively impact environmental systems. It enhances the evaporation process and thereby leads to a faster drying of soils. To address this, we introduce a dual-continuum modeling framework that enables the simulation of fluid flow in both the original, main porous structure, referred to as porous matrix, and the newly formed salt structure. We present two modeling strategies: (1) a coupled-flow model that explicitly resolves mass and energy transport in both the matrix and salt continua, incorporating advective, diffusive, and filling-based exchange terms; and (2) a pseudo-flow model that assumes full saturation of the salt continuum and implicitly captures flow based on evaporative demand, improving computational efficiency. Both approaches reproduce expected saturation profiles, temperature distributions, and evaporation behavior. The resulting evaporation rates are increased, leading to a faster drying out of the porous medium compared to a single-continuum model. The coupled-flow model shows that the precipitated salt remains liquid-saturated for a longer period than the surrounding matrix, thereby sustaining upward water transport; however, its results are sensitive to the parameterization. By assuming full saturation of the precipitated salt, the pseudo-flow model yields the higher evaporation rates while also improving numerical stability. This work presents a first step toward modeling the coupled transport processes resulting from salt precipitation in porous media.