Contamination of ground water by non-aqueous phase liquids (NAPLs) has
received increasing attention. The most common approach to numerical modeling of
NAPL movement through the unsaturated zone is the use of the finite difference or finite
element methods to solve a set of partial differential equations derived from Darcy's law
and the continuity equations (Abriola and Pinder, 1985; Kaluarachchi and Parker, 1989).
These methods work well in many settings, but have given little insights as to why certain
non-ideal flow phenomena will occur. The network modeling method, which considers
flow at the pore-scale, was used in this study to better understand macroscopic flow
phenomena in porous media.
Pore-scale network models approximate porous medium as a connected network
of pores and channels. Two and three-dimensional pore-scale network models were
constructed in this study. A uniform statistical distribution was assumed to represent the
random arrangement of pore and tube sizes. Both hysteristic scanning curves and
intermediate fluid distribution are studied. The simulation results suggested that network
models may be used to predict the characteristic curves of three-phase systems. The
results also suggested that three-dimensional models are necessary to study the three-phase
problems. Two-dimensional models do not provide realistic results as evidenced by
their inability to provide scale-invariant representation of flow processes. The network
sizes used in this study ranged from 10 x 5 (50) to 156 x 78 (12168) pores for two-dimensional
and from 10 x 5 x 5 (250) to 100 x 50 x 5 (25000) pores for three-dimensional
domains. The domain size of 100 x 50 x 5 pores was large enough to provide
descriptions independent of the domain scale.
The one important limitation of network models is the considerable computational
requirements. The use of very high speed computers is essential. Except for this
limitation, the network model provides an invaluable technique to study fluid transport
mechanisms in the vadose zone. / Graduation date: 1996
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/34674 |
| Date | 17 July 1995 |
| Creators | Zhang, Wenqian |
| Contributors | Selker, John S., Istok, Jonathan D. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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