Multiphase capillary rise of multicomponent miscible liquids

The rise of the two-phase (gas and liquid) and two-component (water and ethanol) system in uniform capillaries was analysed by coupling earlier experimental data and a mathematical framework for multiphase capillary rise. These were used to determine how the meniscus position, velocity and acceleration were affected by the physical, chemical and thermodynamic parameters of miscible liquid components. These analyses demonstrated that these parameters could be determined from those of the pure substances, and allowed predicting the system state with residuals less than 1.6%. However, nonlinearities were not anticipated in the way thermodynamic parameters affected the meniscus velocity. Specifically, dynamic contact angle at the three-phase contact line was dominated by the meniscus velocity at low ethanol concentrations and by the thermodynamic parameters at high ethanol concentrations. The hypothesis by which regression equations are used to describe the dynamic contact angle is therefore rejected in favor of mechanistic equations, which may be used for an interpretation of the rise of liquids made of multiple miscible components.