- Nektar-users - imperial.ac.uk

2D unstructured mesh
by Matt Duran 02 Mar '21

02 Mar '21

******************* 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, I currently have an issue with using 2D unstructured meshes in Nektar. The problem seems to be in using NekMesh to convert the .msh to .xml. I have attached the relevant files and an image of the .msh from gmsh and the mesh after being converted to .xml and then .vtu in Nektar. The converted xml appears to have a strange structure, I was wondering if I could get some guidance on how to avoid or fix this issue. Thanks for your time, Matt Duran Mechanical and Aerospace Engineering University of Central Florida [image: image.png] [image: image.png]

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3D case problem
by Alessandro Alberto de Lima 25 Feb '21

25 Feb '21

******************* 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. ******************* 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.

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Warning: Level 0 assertion violation Using Default variable expansion definition for field: u
by ztdepyahoo 25 Feb '21

25 Feb '21

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Processing gmsh file with multiple element types
by Vidhi Zala 24 Feb '21

24 Feb '21

******************* 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. ******************* Hi all, I am trying to use NekMesh to convert a 2D mesh made using gmsh to XML. I am successful in converting a msh file which has only 1 type of element (only quad or tri). However, when I try to convert a mesh that has quads and triangles together, it gives me the following error: Fatal : Level 0 assertion violation Where : nektar++/library/SpatialDomains/MeshGraph.cpp[610] Message : Unable to read composite index range: terminate called after throwing an instance of 'Nektar::ErrorUtil::NekError' what(): Level 0 assertion violation Where : nektar++/library/SpatialDomains/MeshGraph.cpp[610] Message : Unable to read composite index range: Aborted (core dumped) Attached files .geo and .msh are what I am working on. ,-~~-.___._. / | ' \ | |--------. Vidhi Zala ( ) 0 | | | School of Computing \_/-, ,----' | | | Scientific Computing and Imaging Institute ==== !_!-v---v--. University of Utah / \-'~; .--------. / __/~| ._-""|| | vidhi.zala(a)utah.edu =( _____|_|____||________| http://sci.utah.edu/people/vidhi.html I support Ruff Haven Crises Shelter for Homeless Pets <https://www.ruffhaven.org/donate>. Consider a donation today :)

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Error when using compressible flow solver
by Octavio Morales 23 Feb '21

23 Feb '21

******************* 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. ******************* Hi, I am trying to use the compressible flow solver on a very coarse mesh so I can have an idea of how does it works, it is just a cube. I am attachng the xml that i am running with the solver and the screenshot of what appears once I run the command "CompressibleFlowSolver oct.xml". Besides that, I have another question. What is the maximum Mach number that the solver can handle in 3D? Is the compressible flow solver able to simulate in the supersonic regime? and, how can I get the drag and lift force or the shear stress in a hull using Nektar++? Thank you for your time! Best regards, Octavio A. Morales.

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Arpack error
by Matt Duran 22 Feb '21

22 Feb '21

******************* 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, my name is Matt Duran and I am from the University of Central Florida. I have recently begun using Nektar++ 5.0.1 on Ubuntu and was going through the ‘Global Stability Analysis: Cylinder Flow’ tutorial. However, when I ran the ‘IncNavierStokesSolver’ with ‘Cylinder_Direct.xml’ I got the following error: [image: image.png] Arpack is already installed and the relevant sections of the .xml file is shown below. [image: image.png] I was wondering if I could get some assistance on why this error may be happening and how to fix it. Thanks in advance, Matt Duran

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help setting up a Quasi-3D case.
by Alessandro Alberto de Lima 22 Feb '21

22 Feb '21

******************* 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. ******************* Hi. I am trying to run a simulation of a flow past a cylinder. I am using the mesh of the flow stability analysis tutorial and my results are completely two dimensional. No three dimensionalities are present. The xml is attached to this message. Can anyone check if I missed something or what I did wrong? Thanks. Alessandro

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FieldConvert -m addfld (Not working in the recent version)
by Nikesh Yadav 21 Feb '21

21 Feb '21

******************* 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. ******************* Hi, I have updated my Nektar++ and FieldConvert -m addfld feature is not working. Segmentation fault (core dumped) keeps coming. Are you facing the same issue? -- *Thanks and regardNikesh, Ph.D.* *Assistant at Aerodynamics Dept, * *MEiLWarsaw University of Technology, **Warsaw, Poland* *Contact: - **+48 22 234 7523* *Email-id: **nikeshspartan(a)gmail.com <nikeshspartan(a)gmail.com> / * *nyadav(a)meil.pw.edu.pl <nyadav(a)meil.pw.edu.pl>*

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Warning: Level 0 assertion violation Using Default variable expansion definition for field: u
by ztdepyahoo 21 Feb '21

21 Feb '21

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Instability of cylinder wake
by Samik Bhattacharya 21 Feb '21

21 Feb '21

******************* 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. ******************* Hi all, We are using Nektar for a problem related to the instability of cylinder wakes. We are facing some issues. It would be great to get some help from any users in the mailing lists who perform similar analyses using Nektar. Here are our questions: 1. Can we calculate the base flow in Nektar? Or should we just take a Reynolds number below the critical Reynolds number? 2. How do we import Openfoam mesh in Nektar? It will be very helpful to get some insight into these two issues. We will be glad to provide more information. Thanks, Samik

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