ABSTRACT
In porous media studies, wicking is the spontaneous movement of a wetting liquid into a porous medium under the inˆuence of capillary pressure. In this chapter, a relatively new approach of using the single-phase ˆow assumption behind a clearly de ned liquid front in a porous medium is introduced to model the wicking process. Such an approach employs Darcy’s law in conjunction with the continuity equation to model liquid ˆow behind the liquid front. In the rst part of the chapter, governing equations along with pressure, velocity, and suction boundary conditions for modeling wicking in a rigid porous medium are presented. It is accompanied by details on experimental measurement of various properties used in the model. In the following part, the sharp-front model is expanded to include the effects of matrix swelling due to liquid absorption. In the last part, numerical simulation of liquid imbibition using the sharp-front model after employing the nite element/control volume method is introduced to model wicking in more complex wick-geometries, as well as to incorporate nonlinearities arising due to swelling of the solid matrix. Examples of analytical and numerical predictions compared with experimental results are added at the end of each section. The comparisons show that the sharp-front ˆow modeling approach is an accurate and robust method of predicting wicking that can be applied to many practical engineering applications.
