Study of Capillary Filling Dynamics in a Microtube

Abstract

Capillary filling dynamics in a microtube and different aspects of this type of flow has remained a long-acting problem in the last decade considering its numerous applications in various fields.In this study, an attempt has been made to study the influence of certain parameters on the equilibrium height attained by the liquid in the microtube. Lucas Washburn equation has been modified using the concept of phase change and vapour recoil and also accommodating the entrance effects in terms of added mass. The formulated governing equation was used to study
the effect of parameters such as: phase change, different temperature difference across the interface and properties of the liquid numerically using MATLAB. Two different liquids water and ether has been used in the analysis. It was found that phase change by evaporation resulted
in lowering of liquid rise. Also the oscillations in water were found to be damped more than those in ether. It was also seen that as capillary radius increases the temperature difference required to cause oscillations decreases and the oscillations take a longer time to decay. A larger contact angle implied a slower flow. The effect of a ‘dynamic contact angle’, as the fluid propagates inside the tube leads to a larger displacement at a given instant of time.