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download pdf version of PhD book - Universiteit Utrecht

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7. Adsorption under Partially-Saturated Conditions<br />

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .<br />

body sizes are taken from uncorrelated truncated lognormal distributions, and<br />

pore throat sizes are correlated to the pore body sizes.<br />

Probability<br />

0.2<br />

0.15<br />

0.1<br />

0.05<br />

0<br />

0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45<br />

x10 −1<br />

Effective radius [cm]<br />

Figure 7.1:<br />

Distributions <strong>of</strong> pore-body sizes within the pore network model.<br />

7.2.2 Determination <strong>of</strong> the pore cross section and corner<br />

half angles<br />

A key characteristic <strong>of</strong> real porous media is the angular form <strong>of</strong> pores. It has<br />

been demonstrated that having pores with a circular cross section, and thus<br />

single-phase occupancy, causes insufficient connectivity <strong>of</strong> the wetting phase<br />

and as a result poor representation <strong>of</strong> experimental data [Zhou et al., 2000a].<br />

In the present work, pore bodies are considered to be cubic in shape. Pore<br />

throats are assigned a variety <strong>of</strong> cross sectional shapes including circular, rectangular,<br />

and scalene triangular, as it was explained in Section 6.2.2.<br />

7.2.3 Coordination number distribution in MDPN<br />

One <strong>of</strong> the main features <strong>of</strong> the MDPN is that pore throats can be oriented not<br />

only in the three principal directions, but in 13 different directions, allowing a<br />

maximum coordination number <strong>of</strong> 26, as shown in Figure (2.1). Then, to get a<br />

desired coordination number distribution, we fallow an elimination procedure<br />

to rule out some <strong>of</strong> the connections. The elimination procedure is such that<br />

a pre-specified mean coordination number can be obtained. A coordination<br />

number <strong>of</strong> zero means that the pore body is eliminated from the network,<br />

so there is no pore body located at that lattice point. A pore body with a<br />

coordination number <strong>of</strong> one is also eliminated except if it is located at the<br />

inlet or outlet boundaries (so it belongs to the owing fluid backbone). This<br />

means that no dead-end pores are included in the network. Details <strong>of</strong> network<br />

164

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