17.1 Overview

ANSYS FLUENT can be used to solve fluid flow problems involving solidification and/or melting taking place at one temperature (e.g., in pure metals ) or over a range of temperatures (e.g., in binary alloys ). Instead of tracking the liquid-solid front explicitly, ANSYS FLUENT uses an enthalpy-porosity formulation. The liquid-solid mushy zone is treated as a porous zone with porosity equal to the liquid fraction, and appropriate momentum sink terms are added to the momentum equations to account for the pressure drop caused by the presence of solid material. Sinks are also added to the turbulence equations to account for reduced porosity in the solid regions.

ANSYS FLUENT provides the following capabilities for modeling solidification and melting:

• calculation of liquid-solid solidification/melting in pure metals as well as in binary alloys

• modeling of continuous casting processes (i.e., "pulling'' of solid material out of the domain)

• modeling of the thermal contact resistance between solidified material and walls (e.g., due to the presence of an air gap)

• modeling of species transport with solidification/melting

• postprocessing of quantities related to solidification/melting (i.e., liquid fraction and pull velocities)

These modeling capabilities allow ANSYS FLUENT to simulate a wide range of solidification/melting problems, including melting, freezing, crystal growth , and continuous casting . The physical equations used for these calculations are described in Section  17.3, and instructions for setting up and solving a solidification/melting problem are provided in this section in the separate User's Guide.