MODELING OF PERMEABILITY OF POROUS MEDIA WITH MIXEDWETTABILITIESBASEDONNONCIRCULARCAPILLARIES
Keywords:Network Flow, Variational Principle, Wettability, Air-water Interface, Hydraulic Conductance
Hydraulic conductivity of hydrophobic porous media is greater than that of hydrophilic porous
media under the same saturation condition. One of the reasons for this is that the size of the pores filled by
water in hydrophobic porous media is greater than that in hydrophilic media under unsaturated conditions.
The validity of this phenomenon was ascertained through numerical experiments using a pore-network model.
However, the pore-network model with circular tubes could not account for the phenomena sufficiently. Then,
noncircular tubes are employed to take air-water interfaces formed at gaps between grains into account. In
one case of hydrophobic grains, water cannot occupy corners and flows in the center of capillary tubes. In the
other case of hydrophilic grains, water invades the corners first and flows through the corner filaments until
water enters the tube completely. In this study, equilateral triangular and cuspate cross-sections are used, and
the relation between the flow resistance of the tube, which is separated into shape and scale factors, and
capillary pressure is investigated. The computed results show that the flow resistance of center flows could
become smaller than that of full flow and that it leads to higher hydraulic conductivity of hydrophobic porous