A study of the effects of macrosegregation and buoyancy-driven flow in binary mixture solidification

Abstract

A generalized anisotropic porous medium approach is developed for modelling the flow, heat and mass transport processes during binary mixture solidification. Transient predictions are obtained using FEM, coupled with an implicit time-marching scheme, for solidification inside a two-dimensional rectangular enclosure. A parametric study focusing attention on the effects of solutal buoyancy and thermal buoyancy is presented. It is observed that three parameters, namely the thermal Rayleigh number ( Ra v ), the solutal Rayleigh number ( Ra F ) and the relative density change parameter (σ 2), significantly alter the flow fields in the liquid and the mushy regions. Depending upon the nature of these flow fields, the solute enrichment caused by macrosegregation may occur on the top or the bottom region of the enclosure.