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

build issues with versions 5.6.0 and 5.7.0
by Aidan Forknall 04 Jun '25

04 Jun '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. ******************* Hi I am having issues compiling fresh installs of nektar v5.6.0 and v5.7.0 onto a linux workstation. The tar.gz files are downloaded from nektar src. Once extracted I follow the user guide instructions to create a build directory and pull up the ccmake gui (versions of ccmake and cmake on the PC are 4.0.2 stored in /snap/bin/cmake). Only the IncNavirStokesSolver is on, with USE_MPI switched on with thirdparty builds of GSMPI and SCOTCH. When configuring a cmake warning appears regarding policy CMP0177, and when running 'make install' the following error is displayed: ~~~~ CMake Error at CMakeLists.txt:1 (CMAKE_MINIMUM_REQUIRED): Compatibility with CMake < 3.5 has been removed from CMake. Update the VERSION argument <min> value. Or, use the <min>...<max> syntax to tell CMake that the project requires at least <min> but has been updated to work with policies introduced by <max> or earlier. Or, add -DCMAKE_POLICY_VERSION_MINIMUM=3.5 to try configuring anyway. -- Configuring incomplete, errors occurred! make[2]: *** [CMakeFiles/gsmpi-1.2.1_2.dir/build.make:92: ThirdParty/stamp/gsmpi-1.2.1_2-configure] Error 1 make[1]: *** [CMakeFiles/Makefile2:1405: CMakeFiles/gsmpi-1.2.1_2.dir/all] Error 2 make: *** [Makefile:146: all] Error 2 ~~~~ I assume it is an error with gsmpi, however when trying to configure with MPI on without building thirdparty GSMPI, the configuring crashes stating it must be built. Any advice is most welcome. Kind regards, Aidan -------------------------------------------------------------------------------------------------- Aidan Forknall Research Associate - Computational Fluid Dynamics of Spray Combustion Rolls-Royce UTC in Combustion System Aerothermal Processes Department of Aeronautical and Automotive Engineering Loughborough University LE11 3TU, UK --------------------------------------------------------------------------------------------------

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Time-series of Reynold stresses
by Wang Boning 30 May '25

30 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 Nektar++ team, I'm trying to obtain a time series of Reynolds stress. Is there any way to obtain a time series of field-averaged Reynolds stress, or even just at a few specific points? I am currently working with Nektar++ version 5.6.0. However, I am also interested in solutions available in the latest version. I've attempted the following two methods: 1. I tried using the 'history point' filter, but it only outputs variables defined in my session.xml file, specifically uvwp. Is Reynolds stress a predefined variable in Nektar++? Is it possible to define custom variables, such as u'v'? 2. I also tried outputting averaged fields at a high frequency and then post-processing them into a time series. However, this approach leads to enormous disk space occupation, exceeding my authorized storage limit. Is there a more elegant or efficient way to achieve my goal? Best regards, Boning P.S I'm current working on Nektar++ 5.6.0, but I'd like to know solutions for latest version, if there is any.

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Cylinder-Base terminal error question
by 🌸那慢慢🌸 22 May '25

22 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 nektar++ users and developers, I am using the base in the flow-stability-cylinder for calculations, and I want to accelerate the appearance of vortices by setting the initial conditions to (1, 0.2, 0). However, the pressure error in the final results is very large, and the filter does not output a file. I would like to know why this is happening. XML file attachment. Hongtao

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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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Nek5000 to Nektar++ Conversion Problem
by 王兴益 13 May '25

13 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 nektar-users, I am currently working on converting a flow field from Nek5000 to Nektar++ using the FieldConvert utility. Specifically, I used the following command: FieldConvert input.fld output.fld However, it seems to me that the default conversion cannot take different options of points styles into account. When a xml file is included in the command： FieldConvert example.xml input.fld output.fld Although the output.fld file appears to have the correct SHAPE and BASIS settings, the resulting field data still differs significantly from the original Nek5000 solution. On the other hand, even though I manually ensured that the polynomial order settings are consistent between the two formats and that the POINTSTYPE is set to GaussLobattoLegendre, the resulting output.fld file does not appear to fully or accurately reflect the original Nek5000 field data. Some components seem to be missing or incorrectly mapped. I would appreciate any guidance or suggestions you might have on ensuring a more complete and accurate conversion. Are there any known limitations, specific configuration requirements, or pre-processing steps for converting Nek5000 fields to Nektar++ format? Thank you very much for your time and support. Many thanks, Xingyi Wang Harbin Institute of Technology

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Load time-dependent parameter from outside file
by Chen, Qifan 05 May '25

05 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 all, I'm currently working on solving a PDE where a source term which evolves over time. That time dependent parameter cannot be described by a simple function that can be input into .xml; instead, the values can only provided in an external text file. To do it, I can restart Nektar++ with a modified XML file and updated parameters for each time step, but it is very time-consuming due to the initialization of Nektar++. I was wondering if there's a more efficient way to load this time-dependent parameter directly from the external file during the simulation. The methods to load files I find in manual book is not time dependent. Ideally, I'm looking for a method where Nektar++ can load the time-series from the outside file for a parameter. I also wonder the format of such files. Any insights or suggestions you might have on how to achieve this would be greatly appreciated. Thank you for your time and assistance. Best, Qifan

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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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