April 2024 - Nektar-users - imperial.ac.uk

Errors during the use of nektar
by 🌸那慢慢🌸 13 Apr '24

13 Apr '24

******************* 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 Hongtao Cheng and I am from the Harbin Institute of Technology. I have recently begun using Nektar++ 5.3.0 on CentOs and was going through the ‘Global Stability Analysis: Cylinder Flow’ tutorial. However,when I ran the ‘IncNavierStokesSolver’ with ‘Cylinder_Adjoint.xml’ I got the following error: I was wondering if I could get some assistance on why this error may be happening and how to fix it. Hongtao Cheng

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question about extract a plane from flow field
by 王舟阳 13 Apr '24

13 Apr '24

******************* 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 and developers, Sorry to bother everyone here, however, I need some help about extract a plane from a flow field. How might I extract a certain plane from the flow field by location? For example, I have a 3D case, my mesh is A.xml and after simulation the output result is A.fld. And I would like to extract the planar flow field at the location x=0 from A.fld on A.xml mesh. Could I do this by NekMesh or FieldConvert modules? Thanks again to the users and developers of nektar++. Best Regards, Wang Zhouyang

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Reminder - Nektar++ workshop 2024 Registration is open
by Mohsen Lahooti 05 Apr '24

05 Apr '24

******************* 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 everyone, I hope you're all doing well! Just a quick reminder that registration for the Nektar++ workshop 2024 has been open. If you haven't signed up yet, you can do so by following this link: link https://www.eventbrite.co.uk/e/nektar-workshop-2024-tickets-860475053047?af… You can find the workshop schedule and updates on our website. https://www.nektar.info/community/workshops/nektar-workshop-2024/ And the best part? Attendance at the workshop is absolutely free. Can't wait to see you there! The workshop is free to attend. Looking forward to seeing you soon at the workshop! Cheers, Mohsen and Nektar++ Development Team

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Update Parameter in TimeDependent bc
by Guillermo Suárez 02 Apr '24

02 Apr '24

******************* 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 want to update the expression for a time dependent boundary condition for the incompressible solver. I have defined a bc as <D VAR="u" USERDEFINEDTYPE="TimeDependent" VALUE="A*sin(B*t)" /> <D VAR="v"...> <D VAR="p"...> where A and B are parameters I have defined in the <PARAMETERS> section. After N time steps, I want to update the parameter A. Right now I am using a restart approach. Run nektar for N steps with a value of A. A checkpoint file is written at the end. Then, update the config file with the new value for A and use the checkpoint file as a restart, in order to run another N steps with the new value. This is not the most efficient way though. I have read about the "Coupling" capability but I think it is not suited for this problem as A is not a flow variable. Also considered using the "Boundary conditions from file" but my case is 2D and this capability is currently only implemented for 3D. I think the only option is to modify the source code. Specifically, add a piece of code in DisContField::v_EvaluateBoundaryConditions that reads the parameter A from a file and then updates the boundary condition. However, I am not exactly sure how to modify the parameter A that has been read from the session file. Could you please give me some guidance on how to code that? Thank you. Regards, Guillermo

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BndLayerSurface IDs in step file for mesh generation with NekMesh
by Alexander Schukmann 02 Apr '24

02 Apr '24

******************* 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 everyone, to gain experience with NekMesh I first decided to generate a simple 3D boundary layer mesh after working my way through the very helpful tutorials. I started with creating a square duct in Gmsh, exporting the geometry as a STEP file (as recommended in the user guide) and finally feeding it to the mesh configuration file (MCF) and it worked very well. However, since in my case it is necessary to pass the parameter “BndLayerSurfaces” within the MCF, I tried to figure out where this information is stored inside the STEP file. Of course, to first set up the MCF I used the surface information written in the GEO file provided by Gmsh, but I wondered what would happen if I didn’t have a GEO but only a STEP file, e.g. of a more complex geometry created with a more sophisticated CAD tool? How would I know the necessary “BndLayerSurfaces” IDs in such a case? Thanks in advance and all the best, Alex

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Questions about the plane of rotational periodic symmetry
by 谢亚广 01 Apr '24

01 Apr '24

******************* 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

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