Ultrasonic and other Techniques for Measuring Liquid Metal Multiphase Flows

Gas-liquid metal two-phase flows are widespread in many technical fields such as metallurgy or energy and nuclear engineering. In general, the gas injection leads to highly turbulent and complex two-phase flows, which are difficult to predict by numerical simulations. The injected gas bubbles have a distinct influence on the flow pattern and may trigger instabilities in the liquid metal flow. However, almost all experimental investigations are limited to water models so far. This restriction is mainly attributed to the non-availability of suitable diagnostic technique which allow for a satisfactory characterization of the gas bubbles inside the liquid metal. We present laboratory experiments using the eutectic alloy GaInSn which is liquid at room temperature. As an example, ultrasonic techniques were used to investigate the vortex activated entrainment of air at the free surface of a rotating flow. The X-ray radioscopy was applied to visualize the behaviour of Argon bubbles rising in the liquid metal. The measurements reveal distinct differences between water and GaInSn especially with respect to the process of bubble formation, the coalescence and the breakup of bubbles.