Effect of Wetting Phenomenon on Oscillation of Liquid Column in a U-shaped Tube

Abstract

An experimental and theoretical study was conducted to investigate the liquid metal oscillation in a U-shaped tube. Since the surface tension of liquid metal is quite large as compared with usual liquids and its tangential component is dependent on the contact angle appearing at both ends of the liquid column, the characteristics of oscillation should be strongly influenced by the static and dynamic wetting behavior of triple phase contact line. However, the past studies had considered only the inertia, viscous and gravitational force to analyze the dynamics of the oscillation. Here in this study, we proposed an equation of motion in which the hysteresis and velocity dependence of contact angles are properly taken into consideration to estimate the effect of surface tension. In the experiment, the angular frequency ω_d and damping ratio ζ of oscillation were measured for ethylene glycol-water solution and mercury in U-shaped glass tubes, as well as the dynamic contact angles dependent on the contact line velocity. The experimental results were approximated well by the theoretical model proposed here and it is inevitable to include the wetting effect to accurately estimate ω_d and ζ for mercury.