Modeling of solid phase sedimentation during directional solidification in a side cooled cavity

Abstract

PurposeThe purpose of this paper is to present a new numerical approach for modeling the multi‐phase flow during an alloy solidification process. In many solidification processes, advection of solid may have a dramatic effect on bulk convection field as well as on the solid front growth and hence on the macro‐segregation pattern. In the present work, a numerical model is developed to simulate directional solidification in presence of melt convection as well as solid advection in the form of sedimentation. A 2D cavity filled with hyper‐eutectic aqueous ammonium chloride solution (25 wt.% of ammonium chloride) being chilled from one of the side walls has been chosen as the model problem for the numerical simulation.Design/methodology/approachA fixed grid volume averaging technique has been used for solving mass, momentum, energy, and species equation while taking into account the solid phase advection and local re‐melting. Two different criteria have been identified for the solid particles in the mushy zone to be mobile. These two criteria are represented by a critical solid fraction, and a critical velocity. Based on these two criteria, the mushy zone has been subdivided into two different regions namely, an immobile coherent zone consisting of packed equiaxed crystals and a mobile non‐coherent zone where the solid crystals are able to move.FindingsThe numerical results are compared with corresponding experimental observations.Originality/valueThe solid advection velocity and source terms dealing with solid velocity have been calculated using an explicit scheme, whereas the main conservation equations are solved using an implicit scheme.