Modeling Capillary Flow in Complex Geometries

We discuss mathematical models of capillary flow in complex geometries representative of the void spaces formed between fibers in a textile yarn. Moisture transport in textile yarns and fabrics is an important factor affecting physiological comfort. We have extended an existing analytical model for capillary flow in circular tubes to more complex geometries. We validate this model using detailed computational fluid dynamics simulations of this flow. These models are used to understand the effect of geometric and material parameters on moisture transport. In vertical wicking in a bundle of filaments, the model predicts that as the nonroundness of the filaments increases, or the void area between the filaments decreases, the maximum liquid height increases while the initial rate of penetration decreases.