Capillary rise between cylinders

Abstract

The capillary rise of liquid in the gap between two closely spaced parallel cylinders, whose radii may be identical or different, is modelled in this paper. On the basis of the minimum free energy principle and interfacial analysis, the vertical capillary rise of liquid at equilibrium was calculated as a function of distance of separation of the two cylinders. In order to validate our theory, a piece of experimental apparatus was designed and a series of experiments was conducted on it. Compared with the experimental data, our theoretical model gave a reasonably accurate prediction within experimental error except at a small separation of cylinders. Possible experimental errors were discussed. We also showed that the wicking height at equilibrium was nonlinear to the reciprocal of the hydraulic radius.