Hi Jian, Thanks for reporting this. I think I found the cause of this error, so hopefully we will have this fixed soon. Also, one problem I noticed in your .xml file is that in the beginning you have <GEOMETRY DIM="2" SPACE="3"> instead of <GEOMETRY DIM="2" SPACE="2"> Cheers, Douglas ________________________________ From: nektar-users-bounces@imperial.ac.uk <nektar-users-bounces@imperial.ac.uk> on behalf of Jian Yu <yuj@buaa.edu.cn> Sent: 02 October 2016 12:15:50 To: nektar-users Subject: [Nektar-users] Error with Hybrid Meshes Hi everyone, I ran a 2D case with hybrid meshes(triangular and quadrilateral elements), and encountered the following error: Fatal : Level 0 assertion violation eid must be between 0 and 2 Could anyone help me figure out the problem? The xml file is attached. Thank you in advance! Best wishes Jian