ABSTRACT

Wicking or spontaneous imbibition is the suction of a liquid into a porous medium due to the negative capillary pressure created at the liquid-air interfaces. The capillary pressure arises as a result of wetting the surface of the solid particles by the invading liquid that causes a change in the surface energy of the solid phase. In this chapter, an estimation of the capillary pressure through the Young-Laplace equation is presented, and the capillary and hydraulic radii, important parameters in the equation, are discussed. Some important applications of wicking in industry as well as in nature are brieˆy discussed next. Finally, an overview is presented of the different modeling approaches possible for wicking, which include the traditional capillary models, the porous-continuum models, the discrete models, and the statistical approaches.