April 2023 - Nektar-users - imperial.ac.uk

Issue with projectcad
by Ehsan Asgari 27 Apr '23

27 Apr '23

******************* 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 All, If I use "projectcad" on a mesh imported from Gmsh with "Set order 3", I get the following error: Fatal : Level 0 assertion violation > Wrong number of modes? > terminate called after throwing an instance of > 'Nektar::ErrorUtil::NekError' > what(): Level 0 assertion violation > Wrong number of modes? > [gra-login3:09668] *** Process received signal *** > [gra-login3:09668] Signal: Aborted (6) > [gra-login3:09668] Signal code: (-6) If I import a mesh without applying the high-order option in Gmsh, projectcad works fine! How can I resolve this? Any kind of help is appreciated. syavash

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wrong number of modes
by Ehsan Asgari 25 Apr '23

25 Apr '23

******************* 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 All, After I converted the mesh to xml format with order=7 (using NekMesh), I tried to split the first layer adjacent to a wall using the "bl" module with nq=7. However, I get the following error: Wrong number of modes? Is there an incompatibility issue here? Kind regards syavash

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unphysical flow field with higher polynomial order
by Ehsan Asgari 16 Apr '23

16 Apr '23

******************* 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 All, When I increase the polynomial order from 5 to 6, the flow field becomes unphysical. It reaches a frozen state in which the solution does not change with time anymore! I have provided two planar snapshots of the flow fields for p=5 (first) and p=6 (second) below: [image: p=5.jpg] [image: p=6.jpg] As you can see in the images above, p=6 resulted in a weird wake pattern (frozen in time) which is not physical either. My case is a 3-D low-Re flow and I am using the incompressible solver. I was wondering if something may be wrong with what I am doing, or if there is a specific issue with the numerics. Any help would be appreciated. Kind regards syavash

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runtime increases when reducing time step
by Ehsan Asgari 10 Apr '23

10 Apr '23

******************* 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 All, What could cause the iteration time to increase when halving the time step size? I have a 3-D simulation with an initial CFL 0f about 0.67. Once I halve the time step, the CFL reduces to 0.34 but the iteration time increases! I would expect to have a reduction in the iteration time as well. Thanks syavash

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How to use variable polynomial order in compressible solver
by Chengeng Qian 07 Apr '23

07 Apr '23

******************* 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 would like to test the efficiency of p-adaptive method in CompressibleFlowSolver. But I could not find any sample which shows me how to modify the session file. I have tried the same set up found in incompressible solver Tests, as follows, <SOLVERINFO> </SOLVERINFO> <PARAMETERS> AdaptiveMaxModes = 7 AdaptiveMinModes = 4 </PARAMETERS> The CompressibleFlowSolver ran successfully (simulated forward step problem). But I didn't find any difference between the results of "Adaptive Driver" and "Standard Driver". Any suggestions are appreciated. Regrads, Chengeng

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Compute velocity gradient during runtime
by Ehsan Asgari 07 Apr '23

07 Apr '23

******************* 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 All, How can I compute the velocity gradient during runtime? I see a module for FieldConvert but I need to have the gradients during the simulation. Velocity gradients are to be used to calculate the TKE dissipation term. The latter may be used to calculate the Kolmogorov length scale. Is there any filter for this? Or can anyone suggest a workaround? Kind regards syavash

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Reynolds stress field not written
by Ehsan Asgari 05 Apr '23

05 Apr '23

******************* 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 All, I have added the ReynoldsStresses filter to the main Nektar block in my session file: <FILTER TYPE="ReynoldsStresses"> > <PARAM NAME="OutputFile">step95_4_averageField.fld</PARAM> > <PARAM NAME="OutputFrequency">10</PARAM> > <PARAM NAME="SampleFrequency"> 1 </PARAM> > </FILTER> I am doing parallel simulations using 128 cores. However, I get no Reynolds stress fields in my directory. I don't get any errors or warnings either. Am I missing something? Kind regards syavash

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Mesh Generation and Simulation Error
by Ma, Ting-Hsuan 04 Apr '23

04 Apr '23

******************* 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'm currently working on a project involving the periodic hill geometry, and I've encountered an issue with the mesh simulation using Nektar. Despite successfully creating a decent mesh and correctly labeling all physical groups (inlet, outlet, top, and bottom boundary), I've noticed that the vertices at the inlet seem to exhibit a no-slip boundary condition, while the edges themselves seem to follow a periodic inlet/outlet condition. This behavior is unexpected since I've specified a periodic inlet/outlet boundary condition during the simulation. Has anyone experienced this problem before and found a way to resolve it? Any suggestions or insights would be greatly appreciated! A figure of P order of 5 is attached to demonstrate the problem visually. [cid:image001.png@01D966D9.475EC5B0] Thanks, Dustin Ma

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Build nektar with lapack-devel
by Guillermo Suárez 03 Apr '23

03 Apr '23

******************* 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 recently installed the development versions of Lapack and Blas (along with some other libraries) on my local machine. I have tried to rebuild nektar, without any modification to the make file, and it failed because of different errors. I have also tried to with a clean installation of the latest version, also without success - same error. I could not manage to find the issue. I am attaching the CMake log files as well as part of the screen output. Some useful information: mpirun (Open MPI) 4.1.1 cmake version 3.24.2 g++ (GCC) 11.3.1 20220421 Package lapack-devel-3.10.1-1.fc35.x86_64 is already installed. Package lapack-3.10.1-1.fc35.x86_64 is already installed. Package blas-devel-3.10.1-1.fc35.x86_64 is already installed. Package blas-3.10.1-1.fc35.x86_64 is already installed. Any help will be appreciated. Thank you Guillermo

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