April 2025 - Nektar-users - imperial.ac.uk

Nektar++ Workshop 2025
by Chris Cantwell 21 May '25

21 May '25

Dear all, This year's Nektar++ Workshop will be held on the 24th-26th June 2025 at Imperial College London. We are pleased to announce that Tzanio Kolev (leader of the MFEM project) has agreed to give a keynote lecture at the workshop. More information will be made available via the website soon, including how to register. As with recent years, the event is primarily an in-person meeting, but we will aim to allow the talks to be viewed remotely for those unable to travel. Kind regards, Chris -- Chris Cantwell Reader in Computational Engineering Director of Postgraduate Studies (PhD) Department of Aeronautics Imperial College London South Kensington Campus London SW7 2AZ Tel: +44 (0)20 759 45050 Email: c.cantwell(a)imperial.ac.uk www.imperial.ac.uk/people/c.cantwell

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Questions Regarding Eigenvalue Computation in Stability Analysis
by shan xiangjun 01 May '25

01 May '25

******************* 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 Prof, I hope this message finds you well. I am currently conducting a Floquet analysis and using the ModifiedArnoldi method to compute the leading eigenvalues. When the parameter beta is small, the computation converges and produces reasonable results. However, when beta becomes large, all computed maximum eigenvalues turn out to be 1. Increasing the nvec parameter makes it difficult for the calculation to converge. I also tried using the Arpack option and obtained the same results. Could you please advise on how to resolve this issue? Additionally, I would like to inquire about the application scenarios for the BaseFlow_interporder parameter. Can it be used in stability analyses for non-periodic problems? Thank you very much for your time and support. I look forward to your guidance. Best regards, Xiangjun Shan

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Questions about the units of the parameters set in Nektar++.
by Luqi Zhang 08 Apr '25

08 Apr '25

******************* 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++ Team,* I apologize for disturbing you again. I'm currently having trouble setting the kinvis value and noticed that the Nektar++ User-guide sets it to <kinvis=1/Re>. Does this mean that when defining parameters in <PARAMETERS>, they need to be dimensionless , such as timestep, kinvis. If so, how do I define the reference velocity and length in Session.xml for doing dimensionless? Or are they just default values? Moreover, should u,v,p in <BOUNDARYCONDITIONS> and <InitialConditions> be dimensionless, as well? Thank you very much for your time and support. I look forward to your response. Best regards, Luqi Zhang

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Missing Metadata in Checkpoint Files After Switching to Checkpoint Filter in Nektar++ 5.3.0
by z 67 05 Apr '25

05 Apr '25

******************* 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 am encountering an issue with checkpoint file metadata when using the <FILTER TYPE="Checkpoint"> configuration in Nektar++ 5.3.0. I would appreciate your guidance to resolve this. Previously, I used global parameters in session.xml (e.g., IO_CheckSteps) to output checkpoint (.chk) files, which correctly included metadata such as <Time>, <TimeStep>, and <ChkFileNum> in the <Provenance> section. However, after switching to the <FILTER> configuration to *delay checkpoint output until 15 seconds* (see configuration below), the generated .chk files now *lack critical metadata*: <FILTER TYPE="Checkpoint"> <PARAM NAME="OutputFile">un</PARAM> <PARAM NAME="OutputFrequency">10000</PARAM> <PARAM NAME="OutputStartTime"> 15 </PARAM> </FILTER> The missing metadata includes: <ChkFileNum> <Kinvis>1.4<SessionName0><Time><TimeStep> This causes .dat files converted via FieldConvertto *lack SOLUTIONTIME*, preventing time-series visualization in Tecplot. So I just have few questions below: 1. Is there an error in the <FILTER> configuration that causes metadata omission? 2. Are there additional parameters required to preserve <Time>, <TimeStep>, etc., when using the Checkpoint filter, which can solve this problem. 3. Is this a known issue in Nektar++ 5.3.0? Thank you in advance for your assistance. Best regards, Luqi Zhang

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