Mechanical Vibration Impact Studies On The Effect Of Fluid Convection

It is considered an effective method to introduce vibration in crystal growth to produce forced convection for its being able to suppress Marangoni convection. However how vibration has effects on melt is still not defined. Further studies are necessarily needed . In this paper we study the convective flows with axial vibration in Czochralski method by experimental simulation as well as numerical simulation , discussing the influences of various vibrating parameters on melt flows. The buoyancy-driven flow in melt is also studied.In experimental simulation we simulate the flow in water-glycerol mixtures with axial vibration and find that the flow art-greatly influenced by frequency and amplitude of vibration as well as by viscosity and the slenderness ratio. When the amplitude varies continuously the flow in the free surface takes on various forms. It changes from still to steady flow , then to oscillating flow , and until at last to Turbulent convection. When in steaclv convection the flow takes on regular patterns. With the frequency of 100hz ,the steady convection has three common patterns. The velocity of the surface is about 3 orders of the amplitude.We also simulate the axial vibration-induced flow and the buoyancy-driven flow numerically by finite-element method. In this study we find that the convection induced by vibration exists only in a small area near the free surface, which indicates that thevibration-induced convection is just a kind of surface effect. From the vector diagram of velocity , it can be concluded that the direction of the vibration-induced convection is just opposite to that of Marangoni convection and so can be used to suppress the latter.The buoyancy-driven flow of melt with high Pr(greater than 1) gets into unsteady state easier than that with low Pr(far less than 1) under certain slenderness ratio and temperature gradient.