ABSTRACT

Existing analyses on thin film characteristics in porous domains are often built on two- or
quasi-three dimensional geometrically simple pore structures without explicitly
accommodating pore connectivity in the third dimension. More in-depth numerical and
experimental studies are needed to bridge the gap between two- and three dimensional
experimental analyses as well as the gap between three-dimensional numerical and
experimental analyses of pore-scale thin-film characteristics in granular porous media.
Hence, the proposed research, which builds on our ongoing pore-scale interfacial
research, aims at integrating experimental and numerical analyses for better
understanding of thin film characteristics and thermodynamics in three-dimensional
porous media consisting of interconnected arbitrary rough-walled pore geometries.
In this 1-year extension proposal, we aim to develop a thermodynamically sound
free-energy-based multiphase lattice-Boltzmann model (that can handle fluids with highdensity
contrasts and implements thermodynamically-sound solid-fluid interactions). To
obtain data for model verification, we will measure thin film characteristics related to
film formation and distribution in a crushed volcanic tuff. This includes imaging water
distributions as they progress from adsorbed films to capillary held water with increasing
vapor pressure. Based on the images it is possible to estimate the critical separation
distance at which capillary condensation takes place. The film characteristics will first be
measured in geometrically simple two-dimensional flow channels using time-lapse digital
microscopy, and subsequently using computerized microtomography (CMT) for more
complex three-dimensional systems in crushed tuff samples. From the CMT images we
will determine the location and the extent of the capillary condensed regions to be used to
validate new model developments.
Once the model is validated using the two-dimensional experimental data, the
model will be used to simulate thin film formation and distributions in a threedimensional
natural porous medium with hydraulically connected arbitrary pore
geometries. Numerically simulated results on the geometry and extent of capillary
condensed zones will be compared to the microtomography data. The numerical model
will then be used to map the spatial distribution of variables that cannot be measured
experimentally such as fluid density, vapor pressure in thin films, interfacial width, and
three-dimensional curvatures, to subsequently calculate interfacial energies, surface
tension, chemical potentials, and disjoining pressures.
Broader Impacts of the proposed research:
We expect that the findings from the proposed research could have important
wider impacts in diverse fields where processes relevant to the low saturation regime are
of significance, including arid zone irrigation and water management, fate and transport
of contaminants and colloidal particles in the vadose zone, nuclear waste disposal in very
dry climates, enhanced oil recovery, and in planetary sciences. In addition, the project
will provide training for undergraduate and graduate students, as well as a post-doc.

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