Hi Alessandro, It sounds like you may need to run peralign in NekMesh. This orders the faces on the two parallel sides in the same order and ensure triangular faces are aligned. Have you run this module on your mesh? Cheers, Spencer From: nektar-users-bounces@imperial.ac.uk <nektar-users-bounces@imperial.ac.uk> on behalf of Alessandro Alberto de Lima <aalima@usp.br> Date: Thursday, 25 February 2021 at 22:51 To: nektar-users <nektar-users@imperial.ac.uk> Subject: [Nektar-users] 3D case problem This email from aalima@usp.br 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. Hi. My name is Alessandro and I work with prof. Julio Meneghini at University of São Paulo in Brazil. I am trying to model a flow past a cylinder with the Quasi-3D and 3D approach. I have not succeeded yet in both ways. The 3D cases run only in serial? I am getting this message when try to run the case: Fatal : Level 0 assertion violation unable to determine face orientation What is wrong? Thanks. Regards.