# Diverge when using high order **URL:** \ **Category:** Uncategorised\ **Created:** [11 December 2024 16:21 UTC](https://pyfr.discourse.group/t/diverge-when-using-high-order/1197 "2024-12-11T16:21:15Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![fei](https://avatars.discourse-cdn.com/v4/letter/f/59ef9b/32.png) [@fei](https://pyfr.discourse.group/u/fei)\ **Post date:** [11 December 2024 16:21 UTC](https://pyfr.discourse.group/t/diverge-when-using-high-order/1197/1 "2024-12-11T16:21:15Z")
Hello, When I simulate the flow around cylinder, the p3 (fourth order) is ok, when I use P4, the simulation breaks down. So I changed the height of the first layer of wall mesh from 0.025 to 0.2, then the simulation can work. But the countour is discontinous, could someone give me some advice? ---
**Author:** ![fei](https://avatars.discourse-cdn.com/v4/letter/f/59ef9b/32.png) [@fei](https://pyfr.discourse.group/u/fei)\ **Post date:** [11 December 2024 16:23 UTC](https://pyfr.discourse.group/t/diverge-when-using-high-order/1197/3 "2024-12-11T16:23:38Z")
![70c054d5ff2af8c286df96c9948a01a5_720](https://global.discourse-cdn.com/free1/uploads/pyfr/original/1X/5d68c0a0fa306d117ad5097dc77b93fadb4bd332.jpeg) Also, I used the anti-aliasing or modal filiter, is doesn’t work. ---
**Author:** ![p.vincent](https://yyz2.discourse-cdn.com/free1/user_avatar/pyfr.discourse.group/p.vincent/32/225_2.png) [@p.vincent](https://pyfr.discourse.group/u/p.vincent)\ **Post date:** [11 December 2024 23:01 UTC](https://pyfr.discourse.group/t/diverge-when-using-high-order/1197/4 "2024-12-11T23:01:08Z")
Are you able to share your .ini file, and mesh file. And the version number of PyFR. Thanks Peter Professor Peter Vincent MSci ARCS DIC PhD FRAeS Professor of Computational Fluid Dynamics Department of Aeronautics Imperial College London South Kensington London SW7 2AZ UK ---
**Author:** ![fei](https://avatars.discourse-cdn.com/v4/letter/f/59ef9b/32.png) [@fei](https://pyfr.discourse.group/u/fei)\ **Post date:** [12 December 2024 02:03 UTC](https://pyfr.discourse.group/t/diverge-when-using-high-order/1197/5 "2024-12-12T02:03:25Z")
Ok, the mesh and ini file are attached. And I I said wrong, it only works under P1, if you don’t change the height of the first layer of the wall grid. Thanks for your reply. [https://drive.google.com/drive/folders/14BD7V\_eZIAiNLP0nsgL9nEyoEZ5gQznU?usp=drive\_link](https://drive.google.com/drive/folders/14BD7V_eZIAiNLP0nsgL9nEyoEZ5gQznU?usp=drive_link) ---
**Author:** ![p.vincent](https://yyz2.discourse-cdn.com/free1/user_avatar/pyfr.discourse.group/p.vincent/32/225_2.png) [@p.vincent](https://pyfr.discourse.group/u/p.vincent)\ **Post date:** [12 December 2024 05:22 UTC](https://pyfr.discourse.group/t/diverge-when-using-high-order/1197/6 "2024-12-12T05:22:38Z")
And what version of PyFR? ---
**Author:** ![fei](https://avatars.discourse-cdn.com/v4/letter/f/59ef9b/32.png) [@fei](https://pyfr.discourse.group/u/fei)\ **Post date:** [12 December 2024 06:04 UTC](https://pyfr.discourse.group/t/diverge-when-using-high-order/1197/7 "2024-12-12T06:04:16Z")
Sorry, I left that out. The version is 2.1. ---
**Author:** ![fei](https://avatars.discourse-cdn.com/v4/letter/f/59ef9b/32.png) [@fei](https://pyfr.discourse.group/u/fei)\ **Post date:** [13 December 2024 11:56 UTC](https://pyfr.discourse.group/t/diverge-when-using-high-order/1197/8 "2024-12-13T11:56:48Z")
@p.vincent Hello, are you there？ ---
**Author:** ![p.vincent](https://yyz2.discourse-cdn.com/free1/user_avatar/pyfr.discourse.group/p.vincent/32/225_2.png) [@p.vincent](https://pyfr.discourse.group/u/p.vincent)\ **Post date:** [16 December 2024 09:09 UTC](https://pyfr.discourse.group/t/diverge-when-using-high-order/1197/9 "2024-12-16T09:09:13Z")
Hi Fei, When I open your .msh file in Gmsh it appears that nodes are missing at certain element interfaces (see first attached image). Whereas if I remake the mesh myself from your .geo file the missing nodes are present (see second attached image). I haven’t had a chance to run anything yet since I had lots of teaching last week. But as a starting point I would suggest you double check that the mesh is OK. I’ll try and run the case myself later this week. Peter ![Screenshot 2024-12-12 at 05.34.20](https://global.discourse-cdn.com/free1/uploads/pyfr/original/1X/23c890b84b2131853067c365e30b11175cb1a455.png) ![Screenshot 2024-12-12 at 05.36.22](https://global.discourse-cdn.com/free1/uploads/pyfr/original/1X/e17bb3cde7d9b54bc134338f82034cdad9bafcc0.jpeg) ---
**Author:** ![fei](https://avatars.discourse-cdn.com/v4/letter/f/59ef9b/32.png) [@fei](https://pyfr.discourse.group/u/fei)\ **Post date:** [18 December 2024 06:40 UTC](https://pyfr.discourse.group/t/diverge-when-using-high-order/1197/10 "2024-12-18T06:40:37Z")
Thank you for taking time out of your busy schedule to help me. I have checked mesh, it seems ok in my Gmsh. If you have changed the geo file, I was wondering if you could send it to me to see if it works. I’ve already sent you the email address. With best regards