Numerical and experimental modeling of the melt flow in a traveling magnetic field for Vertical Gradient Freeze crystal growth

A Traveling Magnetic Field (TMF) is attractive for Vertical Gradient Freeze crystal growth as it offers a direct flow driving mechanism. A combination of the driving TMF with a superimposed DC magnetic field leads to a damping effect on the fluctuations of the flow velocity, which have to be reduced in order to get a crystal with enhanced material properties. We present numerical and experimental results on the TMF driven flow in an isothermal model fluid in a cylindrical geometry. The TMF is generated by a system of six equidistant coils, which are fed by a three phase current power supply to create an up- or downward directed traveling field. Special attention is focused on the skin effect of the electromagnetic fields for varying field frequency, and its influence on the resulting melt velocity. The stability of the flow was analyzed with help of a spectral code. Critical values for the driving force and the period of the oscillating flow near those critical points were found in a good concordance with experiments.