Quantitative characterization of melt flows in AC magnetic fields

This presentation considers various situations where the flow inside a liquid metal column is driven by different configurations of AC magnetic fields. The ultrasonic Doppler method has been used to determine profiles of the fluid velocity in the ternary alloy GaInSn. The azimuthal and vertical velocity components have been measured allowing for an analysis of both a swirling flow in the horizontal planes and the flow pattern in the radial-meridional plane. In particular, we consider here transient liquid metal flows generated inside a cylindrical container by the superposition of a rotating magnetic field (RMF) and a travelling magnetic field (TMF). The application of the magnetic body forces can be used to create a tornado-like vortex in a closed volume of liquid metal. Moreover, the case of an RMF-driven flow will be discussed which is influenced by an oxide layer at the free surface of the metallic melt. The oxide layer feels the effect of the viscous force arising from the moving liquid beneath and the friction force from the side walls. A complex interaction occurs if the both forces are in the same order of magnitude. In that case, our measurements demonstrate that the occurrence of the oxide layer may lead to an unexpected oscillating behaviour of the bulk flow.