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Raoof, A. and Hassanizadeh S. M., “Adsorption under Partially-Saturated Conditions;
Pore-Scale Modeling and Processes”, prepared for submission to Water Resources
Research.
CHAPTER 7
ADSORPTION UNDER PARTIALLY-SATURATED
CONDITIONS; PORE-SCALE MODELING AND
PROCESSES
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John von Neumann
Abstract
Adsorptive transport, such as transport of viruses and colloids, is of great importance
in studies of porous media. Compared to the number of column-scale
experimental studies, there are very few pore scale modeling studies, especially for
unsaturated porous media. Under unsaturated conditions, principal interactions usually
occur not only at the solid-water (SW) interfaces, but also at air-water (AW)
interfaces. These interactions are greatly influenced by the water content.
In this paper, we study adsorptive transport under unsaturated conditions using a
MDPN model, which allows for a distribution of coordination numbers ranging between
zero and 26. This topological property together with geometrical distributions
are used to mimic the microstructure of real porous media. Transport of adsorptive
solute was calculated by solving local mass balance equations for solute concentration
in all network elements and averaging the concentrations over a large number of
pores. We have employed a fully implicit numerical scheme for transport of adsorptive
solute under unsaturated conditions. The numerical scheme is developed based
on the assumption that the porous medium is composed of a network of pore bodies
and pore throats, both having finite volume.