This work focuses on solute mass transport in a highly heterogeneous two-region
porous medium consisting of spherical low-hydraulic conductivity inclusions,
embedded in a high-hydraulic conductivity matrix. The transport processes
occuring in the system are described by three distinct time scales. The first time
scale reflects the characteristic time for convective transport in the
high-conductivity matrix. The second time scale reflects the characteristic time
for diffusive transport in the low-conductivity inclusions. The third time scale
reflects the characteristic time for convection within the inclusions. Two Péclet
numbers can be defined that compare the time scales and provide qualitative
insight into the net transport behavior in two-region media. To model this
system, four different representations were developed: (1) a Darcy-scale model
that involved direct microscale computation over the entire domain of the
experimental system, (2) a direct microscale simulation computed on a simplified
domain that had similar geometric parameters (e.g. volume fraction of
inclusions) as the complete domain for the experimental system, (3) a volume
averaged model (after Chastanet and Wood [2008]) which uses a constant mass
transfer coefficient and (4) a volume averaged model which employs a
time-dependent mass transfer coefficient. Two different experimental conditions
were investigated: a high flow rate, and a low flow rate. Detailed understanding
of the experimental system was developed, which led to accurate prediction of
the system's behavior for the higher flow rate. Accurate early time fit of the data
was achieved for the experiment with the lower flow rate, while late time
behavior between the models and experimental data diverged. Further
investigations of the experimental system were conducted to examine possible
sources of errors that could lead to an inaccurate description of the system's
properties. Additional mixing within the system, inhomogeneous distribution of
the effective diffusion coefficient and imprecise initial estimates of the hydraulic
parameters are all possible explanations for the inaccurate model representation
of the system's behavior for the lower flow rate case. / Graduation date: 2012
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/30212 |
| Date | 23 May 2012 |
| Creators | Vogler, Daniel |
| Contributors | Wood, Brian D. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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