Experimental investigation of a flow driven by a combination of a rotating and a traveling magnetic field

Velocity measurements in a liquid metal flow were performed in order to study the combined action of a rotating (RMF) and a traveling magnetic field (TMF). In a cylindrical container, an RMF as well as a TMF alone cause axisymmetric volume forces, which drive according axisymmetric base flows. The combination of both fields gives rise to an inherent three-dimensional part of the electromagnetic force distribution. In case of equal frequencies, this drives a three-dimensional flow consisting of a single large-scale helical motion, which implicates an intense mixing of the melt. The necessary admixture of a TMF to accomplish a qualitative change of the flow structure in a given RMF is shown to be two orders of magnitude smaller in case of equal field frequencies compared to the case of differing frequencies.