[qingqingliu]

I am simulating a flow field using pimpleFoam. I want to set an "internal boundary" inside the geometry and specify the velocity on the "internal boundary". Is there a way to do this?

[Tobi]

Yes. Use e.g,. topoSet to get you faces and create a faceSet. After that use createPatch to create a new patch with the faceSet you created previously. You will see the new patch in constant/polyMesh/boundaries. Finally, specify the new boundary conditions for your new patch(s) inside your files (0/*)

[qingqingliu]

Originally Posted by Tobi

Yes. Use e.g,. topoSet to get you faces and create a faceSet. After that use createPatch to create a new patch with the faceSet you created previously. You will see the new patch in constant/polyMesh/boundaries. Finally, specify the new boundary conditions for your new patch(s) inside your files (0/*)

Thanks Tobi for your reply. Because I just want to specify velocity on one face, I used labelToFace as follows:
actions
(

{
name baffleFace;
type faceSet;
action new;
source labelToFace;
value (???);

}

);

In value, I need to input the face ID. Do you know how to get the face ID of an internal face? The boxToFace seems not to work if I just want to find one face.