A fluid dynamics approach to modeling liquid spreading Original Research Article

Predicting dynamic wetting -the displacement of one fluid by another immiscible fluid on a solid surface- is not a trivial task. The usual hydrodynamic assumptions -Newtonian, incompressible liquid, no-slip condition and rigid solid- give rise to a complicting singularity at the contact line (where the solid and the fluid-fluid interface meet) that prevents the use of the dynamic contact angle to determine the shape of the dynamic meniscus. This is a serious situation since dynamic wetting controls processes of interest not only on Earth but also in Space, where the location and movement of fluid in gas-liquid tanks is completely determined by the wetting behavior of the system. In this paper we review the modeling difficulties posed by this problem, and the efforts -theoretical and experimental- aimed at providing a method for predictive calculations of dynamic wetting and identifying controlling physics near the moving contact line.