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

Questions regarding SVV
by Alexander Schukmann 29 Apr '24

29 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 all, I have a few questions regarding spectral vanishing viscosity and hope somebody can help me out. I read in section 9.3.2.2 of Prof. Sherwins book Spectral/hp element methods for computational fluid dynamics that: - only the upper one-third of the spectrum should be treated with SVV - the optimal SVV amplitude level (called diffusion parameter in the user guide) is unknown a priori. Since according to the user guide SVV is activated for modes higher than the product of the cut-off ratio and the expansion order, 1. means the cut-off ratio shouldn't fall below a value of 2/3. I wonder why the default value for all SVV kernels is 0.75 and 2/3? Furthermore, since again according to the user guide, the diffusion parameter is scaled by h/p, how is h evaluated and which value is used for p if different expansions are used for different flow variables? Is p always corresponding to the expansion used for velocity? In section 9.4.2.3 of the book a possible dynamic SVV model formulation is presented. Another question I am interested in, is whether it is possible to activate such a dynamic SVV model within the incompressible N-S solver of Nektar and if not, which procedure would you recommend in order to optimally tune SVV diffusion for a given flow problem? Thanks in advance and all the best Alex Sicher versendet mit [Proton Mail](https://proton.me/).

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Moving source
by dauood Tariq 27 Apr '24

27 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, Is it possible to make the initial condition for example for pressure to move as time is progressing through the simulation using the acoustic solver Kind regards, Dauood Tariq

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module not found
by dauood Tariq 27 Apr '24

27 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, when attempting to run some of the tutorials on ubuntu I am encountering an error. Specifically for FFTW and XxtMultiLevelStaticCond where the response is module not found. I have installed all the necessary components for nektar++. Is there any reason this is happening/ Regards, Dauood

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Nektar++ workshop 2024 - Presentation's abstract
by Mohsen Lahooti 18 Apr '24

18 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, Hope all is well, I would like to thank you for registering and contributing to our workshop with your presentations. Can you please email me the final title of your presentation and the abstract of your work (200 words max) by Friday 3 May 2024. For those that have not registered yet, registration is still open and free, you can register using link below https://www.eventbrite.co.uk/e/nektar-workshop-2024-tickets-860475053047?af… Looking forward to welcoming you at Newcastle in June Cheers, Mohsen And Nektar++ development team

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FieldConvert Surfdistance Module for Quasi-3D Simulations
by Alexander Schukmann 18 Apr '24

18 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, in order to calculate y+ in my quasi-3D simulation of the ReD = 3900 cylinder flow benchmark, I tried the surfdistance module within FieldConvert fo calculate the height of the near-wall prism layer elements. Since surfdistance threw an error indicating that quasi-3D models are not supported, I first used the meanmode module to get a spanwise averaged planar field and then tried it again with that. However, the surface distance is equal to zero over the whole cylinder wall. In the next step I extruded my 2D mesh to 3D with NekMesh extrude utility, but receive the same results: the calculated surface distance is 0 everywhere (see attached pic) with no errors during the calculation. Am I missing something? What would be the correct way to use surfdistance? Thanks and all the best Alex[surf_dist.PNG] Sicher versendet mit [Proton Mail](https://proton.me/).

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Re: [Nektar-users] Questions about the plane of rotational periodic symmetry
by 谢亚广 17 Apr '24

17 Apr '24

Hi Stanisław, Thank you for your help. I have tried adding abstol=1e-8 to the command, but it seems there was no change, which may indicate a problem with how I am creating the rotational periodic mesh in Gmsh. If you have successfully used a rotational periodic mesh and have example files like .geo, .msh, and the mesh's .xml files, could you please share them? This would help me quickly identify and resolve the issues. Thank you once again. Yaguang. -----原始邮件----- 发件人:"Stanisław Gepner" <stanislaw.gepner(a)pw.edu.pl> 发送时间:2024-04-15 15:11:26 (星期一) 收件人: "谢亚广" <xieyaguang(a)iet.cn> 抄送: 主题: Re: [Nektar-users] Questions about the plane of rotational periodic symmetry Hi Yaguang, Try with the abstol=1e-8 parameter for the paralign module: -m peralign:surf1=2:surf2=3:rot=PI:dir=z:abstol=1e-8 For me this makes the difference: You can find about the options for the module by running it with -p proc:<module name>. In the case of paralign: NekMesh -p proc:peralign I am not sure it is listed in the user guide? Best regards, Stanisław Gepner, Ph.D. Faculty of Power and Aeronautical Engineering Nowowiejska 21/25 Str. 00-665 Warsaw, Poland phone +48 (22) 234 51 70 On 14.04.2024 13:54, 谢亚广 wrote: Hello Kaloyan Kirilov, I want to start by using GMSH to NEKTAR, and then use the peralign module in Nekmesh to align p1 and p2 for rotational periodicity. To pinpoint the problem, I have simplified the mesh to its most basic test state. However, no matter what I try, I am unable to achieve the aforementioned requirements using NekMesh -m peralign; it always results in errors. Assuming thi .geo file corresponds to a 2D mesh named test.msh, my operations are as follows: NekMesh test.msh test.xml:xml:uncompress NekMesh -m peralign:surf1=5:surf2=6:dir=z:rot=PI/6 test.xml test_p.xml Subsequently, an error occurs: [ProcessPerAlign] WARNING: Could not find matching edge for surface element 3. Skipping periodic alignment. I hope I have made myself clear. Thank you for your assistance. Best regards, Yaguang. -----原始邮件----- 发件人:"Vivarelli, Guglielmo A" <guglielmo.vivarelli12(a)imperial.ac.uk> 发送时间:2024-04-14 19:30:07 (星期日) 收件人: "谢亚广" <xieyaguang(a)iet.cn>, nektar-users <nektar-users(a)imperial.ac.uk> 抄送: 主题: Re: [Nektar-users] Questions about the plane of rotational periodic symmetry Hi Yaguang, I am not too sure of what you are trying to do, do you just want the two curves to match periodically and then convert the mesh from GMSH to Nektar? If you give me a little more info I may be able to help you. All the best, Guglielmo From:nektar-users-bounces@imperial.ac.uk<nektar-users-bounces(a)imperial.ac.uk> on behalf of 谢亚广 <xieyaguang(a)iet.cn> Sent: 13 April 2024 05:00 To: nektar-users <nektar-users(a)imperial.ac.uk> Subject: [Nektar-users] Questions about the plane of rotational periodic symmetry | This email from xieyaguang(a)iet.cn 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 to disable email stamping for this address. | Hello Kaloyan Kirilov, Thank you very much for providing those solutions. Unfortunately, I am still encountering the same error. I generated the mesh using gmsh, and for testing purposes, I simplified the mesh to the most basic case. Here is the content of the .geo file: SetFactory("OpenCASCADE"); Circle(1) = {0, 0, 0, 4, 0, Pi/6}; Circle(2) = {0, 0, 0, 14, 0, Pi/6}; Line(3) = {2, 4}; Line(4) = {1, 3}; Curve Loop(1) = {3, -2, -4, 1}; Plane Surface(1) = {1}; Transfinite Curve {3, 4} = 3 Using Progression 1.1; Transfinite Curve {1, 2} = 3 Using Progression 1; Transfinite Surface {1}; Recombine Surface {1};//+ Physical Curve("p1", 5) = {3}; Physical Curve("p2", 6) = {4}; Physical Curve("up", 7) = {1}; Physical Curve("up2", 8) = {2}; Physical Surface("plane", 9) = {1}; In this file, I want "p1" and "p2" to represent the periodic boundaries for rotation. Thank you once again for your guidance. Best regards, Yaguang. _______________________________________________ Nektar-users mailing list Nektar-users@imperial.ac.ukhttps://mailman.ic.ac.uk/mailman/listinfo/nektar-users

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Correct number of Dof
by Daniel Garcia 16 Apr '24

16 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 community, how are you doing? I have a question about the FieldConvert module "dof". I suspect that the code counts the total number of modes, but not the real total number of degrees of freedom. For instance, it does not differentiate Ndof between DG and CG nor consider the effects of boundary conditions. Is there another way of computing the real Ndof or a workaround? The script that I checked it ProcessDOF.cpp: " ... void ProcessDOF::v_Process(po::variables_map &vm) { m_f->SetUpExp(vm); int nDOF = m_f->m_exp[0]->GetNcoeffs(); m_f->m_comm->GetSpaceComm()->AllReduce(nDOF, LibUtilities::ReduceSum); if (m_f->m_comm->GetSpaceComm()->GetRank() == 0) { cout << "Total number of DOF: " << nDOF << endl; } }" Thank you for your time, Daniel.

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Questions about the plane of rotational periodic symmetry
by 谢亚广 16 Apr '24

16 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 Kaloyan Kirilov, Thank you very much for providing those solutions. Unfortunately, I am still encountering the same error. I generated the mesh using gmsh, and for testing purposes, I simplified the mesh to the most basic case. Here is the content of the .geo file: SetFactory("OpenCASCADE"); Circle(1) = {0, 0, 0, 4, 0, Pi/6}; Circle(2) = {0, 0, 0, 14, 0, Pi/6}; Line(3) = {2, 4}; Line(4) = {1, 3}; Curve Loop(1) = {3, -2, -4, 1}; Plane Surface(1) = {1}; Transfinite Curve {3, 4} = 3 Using Progression 1.1; Transfinite Curve {1, 2} = 3 Using Progression 1; Transfinite Surface {1}; Recombine Surface {1};//+ Physical Curve("p1", 5) = {3}; Physical Curve("p2", 6) = {4}; Physical Curve("up", 7) = {1}; Physical Curve("up2", 8) = {2}; Physical Surface("plane", 9) = {1}; In this file, I want "p1" and "p2" to represent the periodic boundaries for rotation. Thank you once again for your guidance. Best regards, Yaguang.

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unphysical wiggles in Reynolds stress
by Ehsan Asgari 14 Apr '24

14 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 All, I hope everyone is all rights! Once I raised this issue before but I wasn't able to resolve it. I get unphysical oscillation in Reynolds stress calculated by Nektar++. The footprints of elements are so much that render the results useless. Below is an example: [image: image.png] On the contrary, the time-averaged fields are so smooth: [image: image.png] I am using a quite fine mesh with a p-order of 4: [image: image.png] The case is quasi-3D with a homogenous z-direction. I am wondering what can be done to mitigate the spurious oscillations. Please share your thoughts with me. I appreciate any help you can provide. Kind regards syavash

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Questions about the plane of rotational periodic symmetry
by 谢亚广 14 Apr '24

14 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 Kaloyan Kirilov, I'm not sure how to reply to your messages via email, so I have to start a new discussion each time. I want to start by using GMSH to NEKTAR, and then use the peralign module in Nekmesh to align p1 and p2 for rotational periodicity. To pinpoint the problem, I have simplified the mesh to its most basic test state. However, no matter what I try, I am unable to achieve the aforementioned requirements using NekMesh -m peralign; it always results in errors. Assuming thi .geo file corresponds to a 2D mesh named test.msh, my operations are as follows: NekMesh test.msh test.xml:xml:uncompress NekMesh -m peralign:surf1=5:surf2=6:dir=z:rot=PI/6 test.xml test_p.xml Subsequently, an error occurs: [ProcessPerAlign] WARNING: Could not find matching edge for surface element 3. Skipping periodic alignment. I hope I have made myself clear. Thank you for your assistance. Best regards, Yaguang.

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