Solidification Problem
 

I am trying to create a solidification model in fluent, but I have a few questions. The setup is to create two regions side by side that are 1 cell wide. The region on the left contains air that is at a low temperature of 10K and an artificially high Cp to simulate a low temperature reservoir. The region on the right is the fluid that I want to solidify, I chose water to simplify this. Attached is a simple paint drawing of what I'm trying to achieve. I chose the boundary conditions as shown in the paint pic.

My question is should the multiphase model be selected for this? If I choose a multiphase model and set air as phase 1 and water as phase 2 I am having difficulty specifying where the air is suppose to be and the water. It only lets me do a mixture or one of the phases for the entire model.

Also what type of boundary condition should I choose for the one that separates the two regions? I was told to choose interior, but that is not an option. I currently have it set as a wall.

I tried running the model without the multiphase model on and was not getting thermal penetration into the water from the low temperature reservoir. Therefore I am only seeing two regions at the different initial conditions that I set for temperature. Sorry for the long post, but any help would be much appreciated. Thanks in advance!!!

Bump. Any suggestions? Any help would be much appreciated.
Thanks!

Have you seen tutorial titled 'Modeling Solidification'? Although this tutorial is good for learning about Solidification with Fluent, but I think the solidification has some limitations that you must carefully look in to.

You need not to enable multiphase model. Just define the water as fluid and enter the properties such as liquidus and solidus temperatures, etc. Fluent recognizes the solid and molten phases automatically according to the temperature of any point.