Relaxation Behavior in A Solution System for Crystal Growth under Microgravity

A hydrodynamic model is used to analyze relaxation behavior in a solution system for crystal growth under microgravity. The relaxations of the dimensionless average velocity of fluid Vav, the dimensionless maximum velocity of fluid Vmax, the temperature distribution index Sθ, the concentration distribution index Sø (see text) and the dimensionless average growth rate of crystal V̄cg are calculated under fluctuations of gravity level and the temperature at the growth face of the crystal. The fluctuations are supposed to be perturbations of square pulse with a duration of t0. It follows from the calculations that the effects of the gravity level fluctuation on the fluid velocities are much greater than those of the temperature fluctuation, but the effects of the latter on the indexes Sθ and Sø are much greater than those of the former; the effects of the former on V̄cg are negligible, but the temperature fluctuation at the growth face of the crystal can obviously change the average growth rate of crystal V̄cg. Calculations are also executed for the temperature fluctuation at the surface of the wall of the solute source material. Its effects on V̄cg are negligible too.