Symmetry breaking of melt flow typically encountered in a Bridgman configuration heated from below

A computational model is developed to investigate three-dimensional fluid flow instability and transition to unsteadiness. The simulated domain corresponds to a parallelepiped configuration which is a restriction to the fluid phase of commonly used configurations in crystal growth (viz. Bridgman configuration). In the present work, this problem is studied using three-dimensional simulations and focuses on symmetry breaking and transition to unsteadiness occurring for a low Prandtl number fluid (Pr = 0.01). Three-dimensional simulations presented thus overcome the limitation of the two-dimensional approach. It has been found that the initially steady symmetric flow in the three-dimensional case becomes asymmetric for lower Ra number than for the two-dimensional case. The breaking in symmetry occurs firstly in the transverse plane. For the relatively low Ra number we still have no intensification in the global heat transfer but it appears that the heat transfer increases locally on the bottom and decreases on the vertical active walls. The classical spiral flows typical characterizing the three-dimensional effect (in the third direction) are also identified.