No, for the Rotor, I am using ICEM CFD and there are two types of rotors in a single rotor row: baseline airfoil, and short chord length airfoil. Because of a small difference in chord length, TurboGrid generates different periodic surface shapes, so I built fluid domains in CAD to have the exact same flow passage for two different rotors. In ICEM I created the points at exact same location and matched nodes using a periodic condition.

However, I found it was very very difficult to have exact same nodes on both periodic surfaces between two different rotor fluid domains. I found that the edge size difference is in the order of 5 digits (10e-5) and it is very hard to control that small number.

Hope that I address the issue clearly.

I created the geometry in NX, and found out that the periodic surfaces have very little area difference about ~0.05 mm2. No matter how I tried, I was not able to make identical surfaces on both sides.

In ICEM you should be able to edit the meshes to make it identical, if that is what you want to do.

I know that. What I'm saying is that ICEM generates two different rotor meshes separately. I want them to have identical periodic sides.

Go in ICEM generate a surface mesh on one of the surfaces, transform it over to the matching surface, associate it to that surface, and then generate the volume mesh with those two matching surface meshes pre-defined.

Alternately, you could use the mesh joining function: Do a volume mesh as normal, then make a copy of the mesh transformed across so the periodic faces match up. Do a merge mesh on the matching face, then delete the transformed mesh.

There's two ways I can think of how you can make ICEM make a matching mesh on those faces.

Thank you but it sounds only applicable when there is only one type of airfoil. So that you can copy or transform the periodic surfaces.

When I said two airfoils, they are different ones. So, the meshes for two separate fluid domains should be generated individually in ICEM then they are loaded in CFX.

The two methods I described can be adapted to make matching meshes for two domains with different airfoils but matching periodic faces as well.

But I'm not trying to make them as one fluid domain. It is necessary to have them as separate mesh files and fluid domains. Because there are various configurations of those two airfoils; sometimes they are neighbouring, sometimes not.

Yes, so you take one mesh file, load the other one, make the face mesh match and then delete the second one.

Okay. Let me try that. So is this the first method or the second one?
If possible, can you explain the steps in detail again?

The loading both meshes then deleting one mesh could be applied to both approaches I mentioned earlier.

If you have not used the mesh edit functions in ICEM before I recommend you do a bit of testing before you start with your real geometry. Make a block and try meshing a few surfaces and using these surface meshes, and also test the mesh merge functions. When you understand how the functions work on a simple test geometry then try your actual geometry.