How can I make the solid PCM to sink to the bottom as it melts?

Lim

Hi all, I have an enclosure spherical glass that is contain with phase change material (PCM) that is in its solid state initially. Heat will be applied above the melting temperature of the PCM around the spherical glass. During the melting process of the PCM there will be 2 phases present in the enclosure, the liquid and solid state. The solid PCM will drop to the bottom due to the gravitation force.

A 2d mesh was created and exported out from Gambit.

In Fluent, I used Solidification and Melting function in my simulation. All Material properties of the PCM and glass have set accordingly. The Gravity was also enable with Y=-9.81 in the Operating Condition and the Variable-Density Parameters was also set to an operating density of PCM, that is 777kg/m^3. The Body force weighted under Discretization in Solution Control was also selected.

After iterating for 200 sec, the values for the Liquid fraction was calculated but the simulation did not show the solid PCM sink to the bottom of the enclosure.

How can I make the solid PCM to sink to the bottom as it melts?

Thanks, Lim