An enthalpy-porosity technique is used in Ansys Fluent for modeling the solidification/melting process. In this technique, the melt interface is not tracked explicitly. Instead, a quantity called the liquid fraction, which indicates the fraction of the cell volume that is in liquid form, is associated with each cell in the domain. The liquid fraction is computed at each iteration, based on an enthalpy balance.
The solid velocity due to the pulling of solidified material out of the domain (also referred to as the pull velocity)
The exact computation of the pull velocity for the solid material is dependent on Young’s modulus and Poisson’s ratio of the solid and the forces acting on it. Ansys Fluent uses a Laplacian equation to approximate the pull velocities in the solid region based on the velocities at the boundaries of the solidified region.