14.11.2013 Views

download pdf version of PhD book - Universiteit Utrecht

download pdf version of PhD book - Universiteit Utrecht

download pdf version of PhD book - Universiteit Utrecht

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

8. Numerical scheme<br />

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

ever, under partially-saturated conditions, the choice <strong>of</strong> network elements is<br />

different. Upon drained <strong>of</strong> a pore body, the non-wetting phase occupies the<br />

bulk space <strong>of</strong> the pore. We consider each corner <strong>of</strong> the pore body as a separate<br />

network element (i.e., with its own pressure and concentration). Thus, for a<br />

cubic pore body, 8 different corner elements exist. Fluid flow and solute mass<br />

fluxes between these elements occurs through the 12 edges <strong>of</strong> the pore body (see<br />

Figure 6.3(a)). In the same manner, after invasion <strong>of</strong> the pore throat by the<br />

non-wetting, each edge <strong>of</strong> the pore throat will be a separate network element<br />

(i.e., with separate flow rate and concentration assigned to it). For example a<br />

pore throat with triangular cross section, upon drainage will break into three<br />

network elements, one for each edge flow.<br />

We applied a fully implicit numerical scheme for transport <strong>of</strong> adsorptive solute<br />

under (partially-) saturated conditions, undergoing both/either equilibrium<br />

and/or kinetic types <strong>of</strong> adsorption. Although defining edges <strong>of</strong> drained<br />

pores as separate network elements will increase accuracy <strong>of</strong> modeling, it will<br />

make the computational process heavier, since each network element will be an<br />

unknown variable during the simulation. Under such a conditions, applying an<br />

efficient numerical algorithm becomes very important. We have developed, and<br />

did modeling using efficient numerical algorithms which, though substitution<br />

<strong>of</strong> unknown variables, reduced the size <strong>of</strong> system <strong>of</strong> linear equations by a factor<br />

<strong>of</strong> at least three. This significantly decreased the computational times.<br />

In this chapter we first present numerical scheme for kinetic adsorption under<br />

saturated conditions and then we proceed with transport <strong>of</strong> non-adsorptive<br />

solutes well as adsorptive solutes under partially saturated conditions.<br />

180

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!