Simulating the solidification of water is a demanding test of a numerical procedure to solve phase change problems with convection. This is mainly due to the density inversion that occurs with water close to its melting temperature i.e the density of water reaches a local maximum at about three degrees. This can give rise to interesting fluid flow where the temperature of the liquid is close to the melting temperature. Below is a simulation of the solidification of water in a rectangular cavity. Initially, the solidification front is almost planer until natural convection occurs. After a while a counter clockwise recirculation roll appears at the bottom of the front which accelerates the rate of freezing. The adaptive moving mesh again does a good job of tracking the solidification front and the finite element code correctly predicts the fluid structure.

R. Tenchev, J.A. Mackenzie, T. Scanlon and M. Stickland.

Finite element moving mesh analysis of phase change problems with natural convection.
International Journal of Heat and Fluid Flow, Vol. 26, pages 597-612, 2005.

Braga natural convection problem