I am going to use Fluent rotating reference frame plus VOF multiphase model to simulate air-water flow in an autoclave. I have a question for creating mesh in Gambit.

I already created a cylinder with baffles for autoclave's walls and I also created shaft, rushton blades, etc. rotating parts. The shaft and blades will be set as moving wall with relative velocity adjacent to zone as zero in Fluent.

Should I create a inner cylinder to contain the shaft and blades, and set the fluid contained in this inner cylinder as rotataing reference frame and fluid between this inner cylinder and cylinder for autoclave's walls as stationary. How should I define the boundary condition for the faces of the inner cylinder. Are they "interface" or "interior". Do I unite this inner cylinder with autoclave cylinder or not? Thank you for your suggestion in advance.

I have done the mesh like I described above. In Fluent, after reading mesh, it shows "cannot change interface to interior beacuse there is only on adjacent cell thread". I think the problem occurs due to the inner cylinder I created for MFT. I defined the faces of this inner cylinder as interior. Is it wrong, how should I define it? Thanks.