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, 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. (C) 2007 American Institute of Physics.