Onset of oscillatory flow in a Czochralski growth melt and its suppression by magnetic field

Abstract

Parameter sensitivity on the onset of oscillatory flow and the effect of magnetic field on such an oscillatory flow in the Czochralski melt are investigated. A defect in the crystal known as growth striations seems to be caused by a macroscopic oscillation of the flow, heat and mass transfer in the melt. An oscillatory flow is observed in a model Czochralski melt under a certain condition. It is due to interaction between natural and forced convection in the rotating container. Similar oscillation of flow and temperature fields is also obtained by numerical simulation. The result reveals that the oscillatory flow in the melt is inherent to the system. The critical Reynolds number for the onset of oscillation and the period of oscillation are decreased with the increasing Prandtl number and Rayleigh number. Further, it is confirmed that the oscillatory flow is possible to occur in the real system and can be suppressed by applying the external magnetic field.