Speaker
Description
The unsaturated zone of soils, spanning from the surface to deeper aquifers, mediates exchanges of water, heat, and solutes, and plays a critical role in nutrient transfer and resource availability. Yet, the physical mechanisms governing mixing between infiltrating solutions and resident fluids under unsaturated conditions remain poorly understood. We address this gap through pore-scale numerical simulations informed by synchrotron X-ray microtomography images of a synthetic porous medium (equivalent to sandy soil) at varying liquid-phase saturations. Our 3D flow and transport analyses reveal chaotic dynamics in solute plume deformation and mixing rates, quantified via Lyapunov exponents and mixing volume growth. Both metrics exhibit stronger exponential growth as saturation decreases, under diffusionless and diffusion-relevant conditions, uncovering a previously unknown dependence of chaos on saturation. This behavior is linked to enhanced helical flow motions and shear- and vorticity-dominated regions at lower saturations, as shown by fully resolved flow fields. These findings underscore the dominant role of pore-scale heterogeneity and immiscible phases in mixing efficiency and provide a foundation for predicting reactions in unsaturated porous media, with implications for environmental and industrial applications.
| Country | Switzerland |
|---|---|
| Green Housing & Porous Media Focused Abstracts | This abstract is related to Green Housing |
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