Collaborative Research: Experimental and Numerical Characterization of Thin Films in Three-Dimensional Porous Media

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0610108/0610003Wildenschild/Schaap Existing analyses on thin film characteristics in porous domains are often built on two- orquasi-three dimensional geometrically simple pore structures without explicitlyaccommodating pore connectivity in the third dimension. More in-depth numerical andexperimental studies are needed to bridge the gap between two- and three dimensionalexperimental analyses as well as the gap between three-dimensional numerical andexperimental analyses of pore-scale thin-film characteristics in granular porous media.Hence, the proposed research, which builds on our ongoing pore-scale interfacialresearch, aims at integrating experimental and numerical analyses for betterunderstanding of thin film characteristics and thermodynamics in three-dimensionalporous media consisting of interconnected arbitrary rough-walled pore geometries.In this 1-year extension proposal, we aim to develop a thermodynamically soundfree-energy-based multiphase lattice-Boltzmann model (that can handle fluids with highdensitycontrasts and implements thermodynamically-sound solid-fluid interactions). Toobtain data for model verification, we will measure thin film characteristics related tofilm formation and distribution in a crushed volcanic tuff. This includes imaging waterdistributions as they progress from adsorbed films to capillary held water with increasingvapor pressure. Based on the images it is possible to estimate the critical separationdistance at which capillary condensation takes place. The film characteristics will first bemeasured in geometrically simple two-dimensional flow channels using time-lapse digitalmicroscopy, and subsequently using computerized microtomography (CMT) for morecomplex three-dimensional systems in crushed tuff samples. From the CMT images wewill determine the location and the extent of the capillary condensed regions to be used tovalidate new model developments.Once the model is validated using the two-dimensional experimental data, themodel will be used to simulate thin film formation and distributions in a threedimensionalnatural porous medium with hydraulically connected arbitrary poregeometries. Numerically simulated results on the geometry and extent of capillarycondensed zones will be compared to the microtomography data. The numerical modelwill then be used to map the spatial distribution of variables that cannot be measuredexperimentally such as fluid density, vapor pressure in thin films, interfacial width, andthree-dimensional curvatures, to subsequently calculate interfacial energies, surfacetension, chemical potentials, and disjoining pressures.Broader Impacts of the proposed research:We expect that the findings from the proposed research could have importantwider impacts in diverse fields where processes relevant to the low saturation regime areof significance, including arid zone irrigation and water management, fate and transportof contaminants and colloidal particles in the vadose zone, nuclear waste disposal in verydry climates, enhanced oil recovery, and in planetary sciences. In addition, the projectwill provide training for undergraduate and graduate students, as well as a post-doc.