Wall formation problem in 3D geometry
 

Hello All,

I'm using Fluent in solving flow problem over 3D geometry. When I make two co-centric cylinders (through which fluid is intended to flow) one being partially projected out from the other, the top surface of inner cylinder always forms a "WALL" which is undesired.

I can get rid of this problem by "UNITING" two cylinder volumes but since I need the inner cylinder side surface to be present as Wall, I can't use "Unite volume" option as it clears off the inside portion of the inner cylinder leaving behind only the projected part.

Desired boundary condition:

Top surface of outer cylinder : Velocity inlet
Bottom surface of inner cylinder : Pressure outlet
side surface of outer & inner cylinder : Wall

Can anyone suggest how to tackle this unwanted "WALL" problem?

I have defined zone continuum inside the volumes but still the "Wall" persists.