******************* 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. ******************* Dear Nektar++ users, I am attempting to use Nektar++'s rotational periodic boundary conditions. After generating the mesh, surfaces 5 and 6 in the .msh file can be joined together by rotating around the z-axis by Pi/6. However, when I use the command provided in the help documentation: NekMesh -m peralign:surf1=5:surf2=6:dir=z:rot=PI/6 test.xml test_align.xml the process always fails, displaying the following warning: [ProcessPerAlign] WARNING: Could not find matching edge for surface element 3. Skipping periodic alignment. I have been unable to resolve this issue on my own. If anyone could provide assistance, I would be extremely grateful. Attached to this email, you will find the corresponding .geo, .msh, and .xml files that I have been using for testing. Thank you very much for your help. Best regards, Yaguang