Frequency dependence of an alternating magnetic field driven flow

The flow induced by a single-phase alternating magnetic field (AMF) is studied mainly numerically, and by experiments at mains frequency. For validation, the well-known dependence of the characteristic velocity uc on the magnetic induction B in the turbulent case when the mean velocity scales with the shear velocity, υc ∝ B, is reproduced experimentally and in the simulations. Ultrasonic flow mapping reveals that the eddies in the well believed flow structure of two toroidal vortices one on top of another do not only simply oscillate, but rather the topology of the flow changes slowly on a large scale. Besides such turbulence characteristics, it will be shown that the global flow structure depends strongly also on the frequency of the AMF. An investigation of the change of the characteristic velocity with frequency suggests a quantitative difference of flows in an AMF compared to rotating and travelling magnetic fields.