Finite difference solutions of solidification phase change problems: Transformed versus fixed grids

In using finite difference techniques for solving diffusion/ convection controlled solidification processes, the numerical discretization is commonly carried out in one of two ways: (1) transformed grid, in which case the physical space is transformed into a solution space that can be discretized with a fixed grid in space; (2) fixed grid, in which case the physical space is discretized with a fixed uniform orthogonal grid and the effects of the phase change are accounted for on the definition of suitable source terms. In this paper, recently proposed transformed- and fixed-grid methods are outlined. The two methods are evaluated based on solving a problem involving the melting of gallium. Comparisons are made between the predictive power of the two methods to resolve the position of the moving phase-change front.