SCALING PROCEDURE AND FINITE-VOLUME COMPUTATIONS OF PHASE-CHANGE PROBLEMS WITH CONVECTION

In this paper, solidification problems are investigated from two angle s, namely, the issue of wide disparity of important length scales pres ent in phase change processes, and the finite volume based computation al techniques developed to simulate such processes. To appropriately h andle phase change phenomena, a scaling analysis is presented to bring out the relevant physics at the macroscopic and morphological scales. It is demonstrated that an appropriate choice of the scale is necessa ry to obtain numerical solutions economically. Two different finite vo lume techniques are described in this paper. The first technique invol ves a mixed Eulerian/Lagrangian approach, where the interface is expli citly tracked by means of marker particles, and the field equations ar e solved on an underlying fixed, finite volume grid. The other approac h is an enthalpy model which incorporates the interface information in a field variable called the phase-fraction. This volume averaged tech nique enables the implicit handling of the interface as part of the so lution procedure at the cost of smearing out the discontinuity. Two di fferent phase-fraction update techniques are presented and their relat ive effectiveness and performance discussed. A continuous ingot castin g problem modelled by accounting for the interaction of phase-change a nd turbulent transport is also presented and compared with experimenta l results.