In this paper, a unified model for simultaneous filling and solidification is applied to the two-dimensional filling and solidification of a square cavity. The effects of wall temperature and gate position on solidification are examined. The mixed natural-convection flow and residual flow resulting from the completion of filling are included in this study to investigate the coupled effects of filling and natural convection on solidification. Two different filling configurations (assisting flow and opposite flow due to the gate position) are analyzed to study the effects of residual flow on solidification. The results clearly show the necessity to carry out a coupled filling and solidification analysis, including the effect of natural convection. A numerical algorithm that uses the implicit volume of fluid (VOF) method for filling and a general, Implicit, source-based method for solidification are presented. (C) 2001 Elsevier Science Ltd. All rights reserved.