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Solute Transport in Unsaturated Porous Media with Spatially Correlated Disorder
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  • Ali Saeibehrouzi,
  • Ran Holtzman,
  • Petr Denissenko,
  • Soroush Abolfathi
Ali Saeibehrouzi
School of Engineering, University of Warwick, Centre for Fluid and Complex Systems, Coventry University

Corresponding Author:[email protected]

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Ran Holtzman
Centre for Fluid and Complex Systems, Coventry University
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Petr Denissenko
School of Engineering, University of Warwick
Soroush Abolfathi
School of Engineering, University of Warwick

Abstract

Solute transport in unsaturated porous media is of interest in many engineering and environmen- tal applications. The interplay between small-scale, local forces and the porous microstructure exerts a strong control on the transport of fluids and solutes at the larger, macroscopic scales. Heterogeneity in pore geometry is intrinsic to natural materials across a large range of scales. This multiscale nature, and the intricate links between two-phase flow and solute transport, remain far from well understood, by and large. Here, we use high-resolution direct simulation to quantify solute mixing and dispersion behavior within correlated porous media during drainage under an unfavorable viscosity ratio. Through analysis of flow and transport at multiple realizations, we find that increasing spatial correlations in pore sizes increase the size of the required Representative Elementary Volume (REV). We show that increasing the correlation length enhances solute dis- persivity through its impact on the spatial distribution of low-velocity (diffusion-dominated) and high-velocity (advection-dominated) regions. Fluid saturation is shown to directly affect diffusive mass flux among high- and low-velocity zones. Another indirect effect of correlated heterogene- ity on solute transport is through its control of the drainage patterns via repeated alteration in the connectivity of flowing pathways. Our findings improve quantitative understanding of solute mixing and dispersion under two-phase conditions, highly relevant to some of our most urgent environmental problems. 
Sep 2024Published in Advances in Water Resources volume 191 on pages 104773. 10.1016/j.advwatres.2024.104773