Modeling capillary flow in complex geometries

We discuss mathematical models of capillary flow in complex geometries repr esentative of the void spaces formed between fibers in a textile yarn. Mois ture transport in textile yarns and fabrics is an important factor affectin g physiological comfort. We have extended an existing analytical model for capillary flow in circular tubes to more complex geometries. We validate th is model using detailed computational fluid dynamics simulations of this fl ow. These models are used to understand the effect of geometric and materia l parameters on moisture transport. In vertical wicking in a bundle of fila ments, the model predicts that as the nonroundness of the filaments increas es, or the void area between the filaments decreases, the maximum liquid he ight increases while the initial rate of penetration decreases.