FLOW INSTABILITIES IN A CZOCHRALSKI CONVECTIVE SYSTEM

摘要

The aim of this study is to recognize the flow states and the transition mechanisms between them in a simulated Czochralski convective system. We considered the influence of the crystal rotation effects (up to Reynolds number, Re = 3.9 x 10~3) and the buoyancy (up to Rayleigh number, Ra = 7.2 x 10~7) on the flow. Using velocity fields, obtained by an ultrasonic method, the corresponding 2D Fourier spectra and a correlation function; steady, quasi-periodic and turbulent states were recognized as the Reynolds number was increased. The orthogonal decomposition method was applied to these velocity fields. The numbers of modes involved in the dynamics of turbulent states were calculated. From these results, we have concluded that the rotation effects tend to stabilize the flow, and the thermal gradients play a destabilizing role.