The purpose of this study is to clarify the effect of hydrodynamics and mass transport on the bubble generation in sapphire shaped crystals. The basic idea is that nucleation of bubbles can be anticipated in places were the gas chemical composition is maximum. Finite elements numerical simulation (FIDAP^TM software) is used in order to solve the momentum, mass and chemical species conservation equations in the liquid enclosed in the capillary channel and in the liquid meniscus. A parametric study is performed and the effect of the die geometry and of the physical parameters are clarified. It is shown that the main effect is related to the rejection of the gas at the solid-liquid interface and that forced and thermo-capillary convection can explain the experimental observation of the concentration of micro-bubbles very close to the outer crystal surface in certain cases.

Keywords: bubbles, sapphire, shaped crystals, fluid flow, segregation, numerical simulation

---

The full text of this paper in pdf-Format:

If you came directly to this page, click this symbol to go to the homepage of CRT.