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

Abstract

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, a RMF alone, as well as a TMF alone, cause axisymmetric volume forces, which drive corresponding axisymmetric base flows. The combination of both fields gives rise to an inherent three-dimensional constituent of the electromagnetic force distribution. In the case of equal RMF and TMF frequencies, this combination drives a three-dimensional flow consisting of a single large-scale helical motion, which implies an intense mixing of the melt. The necessary admixture of a TMF to a given RMF to cause a qualitative change of the flow structure is shown to be two orders of magnitude smaller in the case of equal field frequencies compared to the case of differing frequencies.