longitudinal dispersion in nonuniform isotropic porous media

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CHAPTER 5
A COMPARISON OF MODEL CALCULATIONS AND EXPERIMENTAL RESULTS
As discussed in Chapter 3, the random capillary tube network model
cannot predict the permeability of a nonuniform porous medium based on
measurable structural features of the medium. The hypothesis suggested
in Chapter 3 is that "network" effects on the pressure gradient tend to
even out flux rates through pores of different sizes. Although the
model is not suitable to predict permeability, it is still valuable as
a dispersion model. The permeability model can be used to set the
connectivity of the unit cell (see Chapter 3) by comparison with
experimental data for the permeability. Alternatively, some other
permeability model could be used which is able to predict permeability
from structural features. The limited experimental data given in
Chapter 4 support equation (3.11) as a permeability formula, although
there is no theoretical support for this relation. The approach used
here is to match the experimental results for permeability with the
permeability model by adjusting the junction connectivity. Once the
junction connectivity is set, the dispersion model is capable of
predicting the coefficient of longitudinal dispersion based on
structural features of the medium.
5.1 Permeability Calculations; Determining Junction Connectivity
Permeability calculations using equation (3.15) were carried out
with various junction connectivities in an attempt to match the
measured permeabilities. These calculations were carried out using the