Measurement of dynamic surface tension for liquid metal by capillary jet method

Most liquid metals are easily oxidized, causing their surface tensions to vary over time. In this study, a novel method for measuring the dynamic surface tension of a liquid metal during oxidization is proposed. This method is based on the fact that the descent trajectory of a capillary jet ejected horizontally from a small orifice at slow speed depends on the surface tension as well as inertial and gravitational forces. We derive a theoretical model to predict the jet trajectory and determine the dynamic surface tension of the liquid metal by matching the predicted theoretical trajectory to the experimentally measured one. Actual measurements for Wood's alloy at various oxygen concentrations demonstrate that the surface tension decreases to an equilibrium value on a time scale of 10-11 ms at oxygen densities of less than 1.5%, whereas it increases on a time scale of 10-17 ms at greater oxygen densities. This method has the ability to measure dynamic surface tension on a time scale of 1.5-55 ms at an accuracy of ±1.5 ms, making it suitable for measuring the dynamic surface tension of liquid metal in an oxidation process.