Dynamics and morphology of displacement fronts across textural and wettability discontinuities

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Rates and patterns of flow and transport in porous formations are strongly influenced by existence of preferential paths or flow barriers originating from textural and structural changes or long-correlation heterogeneity. Additionally, ever-changing interplay between capillary, gravity and viscous forces in unsaturated B porous media gives rise to a range of complex flow phenomena affecting morphology, stability and dynamics of wetting and drainage fronts. In this project we plan to quantify effects of abrupt changes in capillary restraining forces as a liquid-air displacement front passes from fine to coarse layer, or from wettable to non-wettable domains on morphology of the front and on formation of preferential pathways associated with extreme flow focusing due onset of instabilities. In collaboration with P1 and in house we plan to use lattice Boltzmann (LB) and volume of fluid (VoF) methods to provide detailed account of liquid fragmentation, migration and entrapment at the pore and sample scale. Scaling laws will be developed to characterize flow regimes and conditions for stable vs. unstable displacement scenarios. Concentration of flow to limited pathways significantly shortens mean arrival times of nutrients and contaminants to groundwater relative to predictions for poorly connected or homogenous media. Results of this project will provide guidance for conducting larger scale field experiments and for special upscaling considerations required for estimation of phase distribution sensitive transport properties (gaseous diffusion, hydraulic conductivity, etc).