******************* This email originates from outside Imperial. Do not click on links and attachments unless you recognise the sender. If you trust the sender, add them to your safe senders list https://spam.ic.ac.uk/SpamConsole/Senders.aspx to disable email stamping for this address. ******************* Hello Kaloyan Kirilov, I'm not sure how to reply to your messages via email, so I have to start a new discussion each time. I want to start by using GMSH to NEKTAR, and then use the peralign module in Nekmesh to align p1 and p2 for rotational periodicity. To pinpoint the problem, I have simplified the mesh to its most basic test state. However, no matter what I try, I am unable to achieve the aforementioned requirements using NekMesh -m peralign; it always results in errors. Assuming thi .geo file corresponds to a 2D mesh named test.msh, my operations are as follows: NekMesh test.msh test.xml:xml:uncompress NekMesh -m peralign:surf1=5:surf2=6:dir=z:rot=PI/6 test.xml test_p.xml Subsequently, an error occurs: [ProcessPerAlign] WARNING: Could not find matching edge for surface element 3. Skipping periodic alignment. I hope I have made myself clear. Thank you for your assistance. Best regards, Yaguang.