- Nektar-users - imperial.ac.uk

Acoustic Boundary Condition
by Paul Liu 07 Feb '22

07 Feb '22

******************* 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 was just wondering if there is a paper or documentation outlining how the characteristic non-reflecting boundary condition is formulated for the LEE. I saw a glimpse of it at in the code but was wondering if there are any extra details as I am trying to understand nektar++ better. Thank you everyone *YiLin Liu * *403-397-3457* *liuyilin.liu(a)gmail.com <liuyilin.liu(a)gmail.com>* MASc Student at CML <https://cml.mech.ubc.ca/> UBC

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problems with FieldConvert
by Alessandro Alberto de Lima 02 Feb '22

02 Feb '22

******************* 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 Guys. I'm trying to get lines, planes and boxes interpolated without using paraview, direct from FieldConvert but I'm getting a "Segmentation fault". My case is a 3DH1D simulation. Thank you. Alessandro

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Acoustic Solver Case Questions
by Paul Liu 01 Feb '22

01 Feb '22

******************* 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 run a simple case prescribing an exponential function that is sinusoidal in time for the energy equation in both APE and LEE solvers. I have the analytical solution for this case. The results from APE and LEE solvers agree with each other but the amplitude is quite different from the analytical solution. I have included a more detailed summary (pdf) and all the case setup files in the zip file. I was wondering if I messed up the setup for the cases or is there some kind of scaling on the variables that I am not aware of? Thank you all. *YiLin Liu * *403-397-3457* *liuyilin.liu(a)gmail.com <liuyilin.liu(a)gmail.com>* MASc Student at CML <https://cml.mech.ubc.ca/> UBC

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P-adaptation
by Niccolò Tonicello 31 Jan '22

31 Jan '22

******************* 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 using Nektar++ compressible flow solver. I noticed the p-adaptive algorithm can be used to optimize the computational cost but I found practically no information on how to use it (in the user's guide). Can anyone send me a simple example on how to use it? Right now, the solver part of my .xml file looks like this: <SOLVERINFO> </SOLVERINFO> Many thanks for your help! Niccolò Tonicello,

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Servers down?
by Aidan Forknall 28 Jan '22

28 Jan '22

******************* 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 recompile Nektar++5.1.0 however the src index is unavailable and when taking from GitLab the compilation fails when trying to download thirdparty gsmpi, it seems the Nektar++ server is down. Can you please advise me as to when the servers will be restored? Kind regards, Aidan Forknall -------------------------------------------------------------------------------------------------- Aidan Forknall Doctoral Researcher in Computational Fluid Dynamics for Combustion School of Aeronautical, Automotive, Chemical and Materials Engineering Loughborough University LE11 3TU, UK --------------------------------------------------------------------------------------------------

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Mattermost members exceeded? other alternatives?, Linear multi-step boundary conditions
by Kurt Sansom 22 Jan '22

22 Jan '22

******************* 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 nektar++ community, It seems like I can't join the mattermost as the membership is exceeded. What other alternatives should I consider to get feedback about ideas or questions? It seems like the email list gets minimal attention (historically) especially for someone who is peripherally involved? I would like to throw out some ideas every once in a while, but I'm not sure the best place to put them. My current one has to do with implementing time dependent boundary conditions that are a function of the time stepping method. I.e. for a boundary condition that manages a state similar to a time stepping method should it be constrained to the type and kind of time stepping method. For example, if a Linear multistep method such as adams bashforth is employed. Any boundary condition that uses some derived quantity to define the boundary condition could be defined with a similar method or if you use a different method (Backwards finite difference) wouldn't you lose accuracy at the boundary? How does that affect the global solution? Maybe the broader topic is coupling different fidelity models? Because any time dependent boundary condition that uses derived quantities is essentially solving some kind model and applying it at the boundary. Happy random quandaries, Regards, ~Kurt -- Kurt Sansom

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Regarding a PhD position at Coventry University
by Abhishek Kumar 24 Dec '21

24 Dec '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 all, I have got a PhD position at Coventry University with the proposed titled "Advanced stability of fusion-relevant liquid metal flows." The project aims to develop an understanding of how the intense magnetic field influences the onset of turbulence in a 180-degree bend. I have briefly discussed the project in the Nektar++ workshop. If you find anyone interested for the position then please share the information. The application deadline is *31 January 2022*. For the details of the project and application procedure, please follow this link: https://www.coventry.ac.uk/research/research-opportunities/research-student… Best wishes to you and a merry Christmas to you and your families. With regards Abhishek -- --------------------------------------------------------------------------------------- Abhishek Kumar Assistant Professor (Research) Centre for Fluid and Complex Systems Coventry University, Coventry CV15FB The United Kingdom Web: https://sites.google.com/view/abhishekkir ---------------------------------------------------------------------------------------

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Periodic boundaries
by Marc Goldbach 23 Dec '21

23 Dec '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 attempting to run a channel flow simulation with 2 sets of periodic boundaries (inlet/outlet and the spanwise boundaries), but am running into issues. When running the solver, I get the following error: Fatal : Level 0 assertion violation Local copy of allCompPairs not the same for all ranks My boundary conditions are defined as follows: <BOUNDARYREGIONS> C[1]  C[2]  C[3]  C[4]  C[5]  C[6]  </BOUNDARYREGIONS> <BOUNDARYCONDITIONS> <REGION REF="0"> </REGION> <REGION REF="1"> </REGION> <REGION REF="2"> </REGION> <REGION REF="3"> </REGION> ... <\BOUNDARYCONDITIONS> The bash script uses the following commands to convert the mesh and run thet solver: NekMesh -m peralign:surf1=1:surf2=2:dir=x -m peralign:surf1=3:surf2=4:dir=y channel.msh channel.xml srun --mpi=pmix_v3 -N $SLURM_NNODES IncNavierStokesSolver -v --use-scotch channel.xml settings.xml Can anyone provide some help on what needs to be done to correct this? The simulation runs without issues when I have only one set of periodic boundaries specified (at the inlet/outlet). Regards, *Marc Goldbach* PhD Student, Department of Mechanical Engineering University of North Carolina at Charlotte

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issue with FieldConvert
by Shukla, Khemraj 06 Dec '21

06 Dec '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. ******************* Dear All- I was trying to use FieldConvert on chk field to .dat file with range option. It was converting the file but the extracted cube has the same size as the original file. I will really appreciate your help. Thank you very much! Regards Raj

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Periodic BC with rotation
by Stanislaw Gepner 07 Nov '21

07 Nov '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 looking at the periodic BC with a rotation in a 2D flow. I managed to get NekMesh to work and align a PI-rotational boundary pair. I included a Rotated tag in the BOUNDARYCONDITIONS (it seems the tag is not used in 2D anyway), but what I get is not what I have expected. Consider attached figure, I have an outflow on top-right, rotated to bottom-right and I was expecting to see an inflow there. I had a look at the DisConstField.ccp, and there is a small piece of code setting everything up (~4,5k lines of code), and from what I understand rotation is not accounted for in a 2D case. My question is than: 1. Am I looking at the periodic-rotation BC in a wrong way? 2. Where are periodic BC enforced? I was unable to find the spot where I could just plug a *-1 to reverse the flow. Cheers, Stan -- Pozdrawiam, dr inż. Stanisław Gepner, *Wydział Mechaniczny Energetyki i Lotnictwa* Nowowiejska 21/25 Str. 00-665 Warszawa, Polska tel. +48 (22) 234 51 70 <http://www.pw.edu.pl/>

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