Numerical and experimental modeling of VGF-type buoyant flow under the influence of traveling and rotating magnetic fields

Numerical and experimental modeling of a VGF-type (VGF—vertical gradient freeze) buoyant flow under the influence of both traveling and rotating magnetic fields (TMF and RMF, respectively) is presented. Low-temperature flow experiments were carried out using a GaInSn alloy as model fluid. Radial heating and cooling of the melt leading to a meridional double vortex flow like in typical VGF growth was introduced using a double-walled melt container. The flow was found to be significantly influenced by the mutual interaction of buoyant and electromagnetically driven forces. With increasing axial temperature difference, the buoyant flow becomes more concentrated in the upper and lower part of the melt leaving an extended melt zone with low flow velocity around the mid-height. Furthermore, VGF-type buoyancy is found to stabilize TMF- and RMF-induced melt flows. Besides, the time evolution of the flow just above the stability threshold is studied. In the case of combined VGF-type/RMF flow complex fluctuation patterns are observed, which depends sensitively on the applied thermal field.

► Low-temperature flow experiments were carried out using a GaInSn alloy as model fluid.
► For the first time, TMF-/RMF-induced flows in combination with VGF-type buoyancy.
► Buoyancy has a stabilizing effect on the TMF or RMF induced melt flow.
► Peculiar time evolution beyond stability threshold of combined VGF-type/RMF flow.