HR: 09:40h
AN: H41H-07    [Abstracts]
TI: Impact of Drainage Front Morphology on Gas Diffusion in Unsaturated Porous Media: A Lattice Boltzmann Study
AU: * Chau, J F
EM: chau@engr.uconn.edu
AF: University of Connecticut, Dept. of Civil & Environmental Engineering 261 Glenbrook Rd. U-2037, Storrs, CT 06269 United States
AU: Or, D
EM: dani@engr.uconn.edu
AF: University of Connecticut, Dept. of Civil & Environmental Engineering 261 Glenbrook Rd. U-2037, Storrs, CT 06269 United States
AB: The effect of a pore-scale phenomenon (flow morphology) on a macroscopic transport property (effective gas diffusion coefficient) is analyzed using the lattice Boltzmann method (LBM). Various flow regimes for two-phase flow in porous media have been defined: stable displacement, capillary fingering, and viscous fingering. The dominance of one regime over another in a porous medium of interest is controlled by the relative magnitudes of gravity, viscous, and capillary forces, which can be quantified with three parameters: Bond number Bo, capillary number Ca, and their difference, Bo-Ca. It has been shown that macroscopic transport properties in porous media are highly dependent on fluid configuration. Since the three flow regimes exhibit very different fluid morphologies, it seems likely that flow regime would have a significant effect on diffusion. In order to investigate the effect, forced drainage from a 2-D porous medium is simulated, and resulting flow patterns are analyzed and compared to the experimental results from the literature. The LBM adequately reproduces expected flow morphologies under a range of applied drainage velocities and gravitational accelerations (i.e., Capillary and Bond numbers). Gas diffusion through the unsaturated domain at various water contents is then simulated for two cases: stable drainage front and a front exhibiting viscous fingering. The macroscopic effective diffusion coefficient as a function of water content is measured and compared for both cases; significant reductions are found in the effective diffusion coefficient in the viscous fingering case relative to the stable displacement case.
DE: 1805 Computational hydrology
DE: 1847 Modeling
DE: 1866 Soil moisture
DE: 1875 Vadose zone
DE: 1894 Instruments and techniques: modeling
SC: Hydrology [H]
MN: Fall Meeting 2005