[kennyboy]

Hi there

I cant seem to find a solution to this on the forum so I thought i will just create a new thread.

What happens is I have a geometry but I subdivided it into several parts. And so there will be interface boundaries within this geometry itself. After I defined all the relevant walls on ANSYS designModeler, done with the meshing and export the mesh into fluent, fluent identified several of the interface boundaries within the geometry as walls instead of interior.

So I tried to change it under the Boundary Conditions tab of fluent but it cannot work. The error message was like "cannot change wall-xxxx- to interior because adjacent cell threads are of different types".

So I thought I might have forgotten to form the sub divided parts into a single part but I already did (selected all the subdivided parts, right click, form new parts in designmodeler). And I even selected all of these parts to be fluid.

So I was hoping someone can enlighten me what could have went wrong? How can I change these inter-sub divided volumes' interfaces into interior?

Thank you!

[LuckyTran]

Probably you ended up with several cell zones. Check in the cell zone conditions to see how many zones you have there.

You cannot have an interior interface between different cell zones. Even if you specify them as the same type (all fluids) they are still distinct domains.

You can go back to the mesher and try to fix the settings or you can merge all the cell zones together using the commands in fluent. In /mesh/ in TUI and the mesh section in the GUI ribbon. It might be called something funny like fuse instead of merge.

Only after all the cell zones have been merged can you change to an interior type. You should also merge the redundant boundaries(the wall wall-shadow pairs) when you do this. I forget which order to do it in (either boundaries first then zones or zones then boundaries).

[kennyboy]

Originally Posted by LuckyTran

Probably you ended up with several cell zones. Check in the cell zone conditions to see how many zones you have there.

You cannot have an interior interface between different cell zones. Even if you specify them as the same type (all fluids) they are still distinct domains.

You can go back to the mesher and try to fix the settings or you can merge all the cell zones together using the commands in fluent. In /mesh/ in TUI and the mesh section in the GUI ribbon. It might be called something funny like fuse instead of merge.

Only after all the cell zones have been merged can you change to an interior type. You should also merge the redundant boundaries(the wall wall-shadow pairs) when you do this. I forget which order to do it in (either boundaries first then zones or zones then boundaries).

Hi LuckyTran,

thanks for the advice. I tried to fuse them in fluent but it cannot be done and there is a message as follows: "Not fusing zone xx and xx, coupled zones."

[kennyboy]

ok managed to sovle my problem in the end. cos i cut my control volume into smaller sub-volumes (for structured meshing) and they are defined as separate parts. which explains why the inter-boundary surfaces are defined as walls (instead of interior) because fluent sees these sub volumes as separate entities.

so what i did was to 'form new parts' in designmodeler so all the sub volumes are now '1 part'. then my inter-boundary surfaces are all interior now.