Learning Forum

[Dubey92]

For melting of a solid to liquid, as I understand FLUENT assumes the solid to be a fluid of high viscosity. If the Solidification/Melting is "on", we can provide Solidus and Liquidus temperatures and FLUENT will add the Darcy force term.

1. Now, under the materials properties, which viscosity should we provide? Is it the liquid viscosity we provide and FLUENT will automatically take a high viscosity for the solid phase? Or we provide a temperature dependent viscosity where we can give a high viscosity like 1000 in the solid phase and then the liquid viscosity after melting point.
2. Similarly, when using VOF, how to give surface tension coefficient between a gas and a solid? My solid melts after the melting point and I have only surface tension between the gas and the liquid phase.

[Rob]

Read how the model works, you may want a temperature dependent viscosity but don't worry too much about the "solid" part of the curve, just make sure the viscosity range covers the full temperature range you're modelling.
In VOF surface tension is set in the phase interaction panel, with the solidification & melting model there is no "solid", it's a liquid with some extra terms applied.

[Dubey92]

Thanks a lot for your reply. I read about it and found that viscosity of solid is not that important as Fluent itself adds a Darcy's source term in the momentum equation to suppress the velocity in the solid phase.
As for the surface tension, I know that Fluent assumes the solid to be a fluid of high viscosity. My main doubt was about the Marangoni stress term which I was adding through a UDF. I realised that I should add it only after temperature of a cell has reached above the melting point.

[Rob]

You'll need a value for the "solid" part too, but you can set that as a low value.

[Dubey92]

Thanks for your suggestion. I think this was causing some error.