modeling two interacting volumes
 

My case: I have a pipe passing through a box, the box just contains air. I there is a source of radiation on one wall of the box which propagates into the box and it should also pass through the wall of the pipe to interact with the fluid in the pipe. I meshed the pipe and the box around it separately. and I do not know what to do so that radiation can pass through the wall of the pipe but water not go into the box. How would I make the two meshed two interact. I tried to unite 2 faces diving the meshed but gambit shows error.

show me ur image. I think u need to do interface.

here is my geometry
 

Hi, and thank you for replying to my thread.

I have attached the geometry to understand my problem. Let me know how i can do the interfacing method.

Banerji,

is that the cube is solid and the cylinder is fluid (or a fluid flow in pipe) ?
If both is fluid, do u need to have fluid passing through each other freely? or passing throught with porous surface?

If ur case just want to have it passing through each other freely, u may set the surface of the cylinder as a interface BC, and the cube's hole surface as inteface BC.
Then u go to Define>Grid inteface. put a random name and select the surface of cylinder on left list and hole surface on right list. Click Create.
This will make the touching surface able to pass through fluid. But the non touching surface will automatically become walls.

Take a try.

The cube contains air and the cylinder contains water. The only thing that passes through their interface is radiation, the material I am planning to use for the two volumes divider(or interface) is quartz; which is transparent to radiation but the fluids in both volumes are not interacting. do you think that will work?

When trying i got some errors like: " cannot create surface from sliding interface zone"

and a warning: "Attempted to correct hace handedness of 1 face out of 168 faces on the sliding interface zone 21"

do you have an idea on what these errors mean?

Maybe u should try to use Boolean to create the feature u said.
Just draw up a cube and cylinder. Goes to Volume tab, click Boolean (the symbol with 2 circle intersect ) . Choose Subtract.
Select cube for the first volume and Cylinder for the 2nd volume. Tick "Retain" to keep the cylinder after subtract.

Anyhow, what u do is multiphase flow(fluid and gas is different phase). I don't think interface can solve it.
I will suggest u create a pipe for ur cylinder and define the pipe as the material u said. No interface is needed since there is no fluid pass through each other.
I not sure if this can work out. Let me know if u do.