SUPPRESSION OF TEMPERATURE OSCILLATION IN CZOCHRALSKI CONVECTION BY SUPERIMPOSING ROTATING-FLOWS

A numerical study was made of a control technique of transient oscilla tory flows in Czochralski convection. The suppression of temperature o scillation was achieved by changing the rotation rate of crystal rod O mega = Omega(0)(1 + A(S) sin(2 pi/t(p)f(S)t)), where A(S) denotes the dimensionless rotation amplitude and f(S) the frequency. Based on the inherent oscillatory time period of the melt (t(p)), the suppression r ate of temperature oscillation was characterized by the mixed convecti on parameter Ra/(Pr Re-2). This parameter ranged in the study 0.225 le ss than or equal to Ra/(Pr Re-2) less than or equal to 0.929, which en compasses the buoyancy- and forced-convection dominant regimes. Comput ational results revealed that the temperature oscillation can be suppr essed significantly by adjusting the control parameters. The uniformit y of temperature distribution in space and in time near the crystal in terface was scrutinized. Copyright (C) 1996 Elsevier Science Ltd.