- Nektar-users - imperial.ac.uk

About the LBB condition
by shan xiangjun 13 Jul '22

13 Jul '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. ******************* Dear all: When the continuous or discontinuous Galerkin method is used to solve the incompressible N-S equation, can the “checkerboarding” of the pressure field be avoided if the LBB (or inf-sup) condition is satisfied? Can anyone help me? Thank you very much. Best regards, Shan 从 Windows 版邮件<https://go.microsoft.com/fwlink/?LinkId=550986>发送

2 1

Basic questions as a beginner
by Marc 11 Jul '22

11 Jul '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 came across Nektar++ and was very interested in it. As very new to it, I have tons of questions about Nektar++ of which I concerned the most: - The tutorials using Jupyter notebook on the website seem in completed. The mesh files and .xml configuration file are not available in most cases. Any suggestions how to fetch them somewhere else? - I basically play with Incompressible NS flow. Compared with finite volume method, e.g., OPENFOAM and ANSYS FLUENT, how is the efficiency of Nektar++? - Any suggestions how to begin with Nektar++? Marc Ph.D. student

2 1

Re: [Nektar-users] Defining complex initial conditions in session files
by Vidhi Zala 08 Jul '22

08 Jul '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 Mike, Yes, min() seems to be the culprit. If you point me to where can I implement it, that would be great. I can find a workaround to not use min () in initial condition but the function is complicated enough already. V On Thu, 7 Jul 2022 at 05:30, Mike Kirby <kirby(a)cs.utah.edu> wrote: > > Hi - > > Did you try the expression without min(.) to verify that min is the > problem? Min may not exist in the set of functions implemented > (currently), but could be added. > > Cheers > Mike > > > > On Jul 7, 2022, at 3:33 AM, Vidhi Zala <vidhi.zala(a)utah.edu> wrote: > > Hi everyone, > > I am looking for a way to define initial conditions which contain min() > function. Can someone point to an example/syntax for the same? I am > currently getting an error saying > > Message : Equation::Equation() fails on expression > [(0.25*(1+cos(PI*min(sqrt(pow(x-bell_x0,2) + pow(y-bell_y0,2))/bell_r0, > 1.0))))] > > Thanks > V > -- > > ,-~~-.___._. / | ' \ | |--------. Vidhi Zala > ( ) 0 | | | Intel Corp. > \_/-, ,----' | | | School of Computing > ==== !_!-v---v--. Scientific Computing and Imaging Institute > / \-'~; .--------. University of Utah > / __/~| ._-""|| | vidhi.zala(a)utah.edu =( _____|_|____||________| http://sci.utah.edu/people/vidhi.html > > > > ---- > R.M. Kirby > Professor, School of Computing > and Scientific Computing and Imaging Institute > University of Utah > > -- ,-~~-.___._. / | ' \ | |--------. Vidhi Zala ( ) 0 | | | Intel Corp. \_/-, ,----' | | | School of Computing ==== !_!-v---v--. Scientific Computing and Imaging Institute / \-'~; .--------. University of Utah / __/~| ._-""|| | vidhi.zala(a)utah.edu =( _____|_|____||________| http://sci.utah.edu/people/vidhi.html

1 1

Defining complex initial conditions in session files
by Vidhi Zala 07 Jul '22

07 Jul '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 am looking for a way to define initial conditions which contain min() function. Can someone point to an example/syntax for the same? I am currently getting an error saying Message : Equation::Equation() fails on expression [(0.25*(1+cos(PI*min(sqrt(pow(x-bell_x0,2) + pow(y-bell_y0,2))/bell_r0, 1.0))))] Thanks V -- ,-~~-.___._. / | ' \ | |--------. Vidhi Zala ( ) 0 | | | Intel Corp. \_/-, ,----' | | | School of Computing ==== !_!-v---v--. Scientific Computing and Imaging Institute / \-'~; .--------. University of Utah / __/~| ._-""|| | vidhi.zala(a)utah.edu =( _____|_|____||________| http://sci.utah.edu/people/vidhi.html

2 1

Correct approach to add fluid Blowing and/or suction at a Plane Poiseuille Flow wall
by Debbahi Saad 07 Jul '22

07 Jul '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. ******************* Dear all, I use Nektar++ mainly to study time dependent 3D plane Poiseuille flow, using the Incompressible Navier-Stokes Solver (using a fully 3D configuration), I'm wondering what would be the best approach to add Blowin and/or Suction at the wall ? Looking into the user-guide version 5.1.0 section 3.5.1- XML-Session-File>Forcing>Absorption seems to be a usable feature in this context Is there an efficient and suitable approach to add these perturbations to the flow ? Any general guidelines to achieve this are really appreciated, Thanks in advance, Kind regards, Saad

3 5

2D Navier Stokes mesh generation
by 董智康 06 Jul '22

06 Jul '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 learning 2D Navier Stokes equations by using Nektar++, it is a really nice tool! However, I met a problem. I’m not sure how to customize my own 2D mesh, say change the flow domain, radius and position of cylinder. I have read though your tutorials. It seems like I need a CAD .step file to achieve my goal. But I also noticed that Nektar++ can generate meshes of NACA wings. So I’m wondering if I can do the similar things to generate meshes of a cylinder. Best, Zhikang

2 1

Parallel FieldConvert output in one single vtu file ?
by Debbahi Saad 15 Jun '22

15 Jun '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'm on Nektar version 5.1.0, ending with datasets composed of moderate size files in numbers reaching few hundreds using the Incompresible Navier-Stokes Solver, I just want to use parallel FieldConvert to speed up the conversion process (which actually provide a real gain in speed) and produce a single vtu file, since opening *.pvtu format datasets gave an error in paraview-openmpi-5.9.1 , The command I'm using for parallel FieldConvert looks like this: mpirun -n 16 FieldConvert -m mapping model.xml model_i.chk model_i.vtu this creates n .vtu files under a .pvtu header, which as I reported earlier gives rise to this error: > ERROR: In > /builddir/build/BUILD/ParaView-v5.9.1/VTK/IO/XML/vtkXMLPDataReader.cxx, > line 315 > > vtkXMLPUnstructuredGridReader (0x55ffb1431450): File for piece 0 cannot be > read. > Is it possible to produce one single .vtu file out of parallel FieldConvert ? Thanks in advance, any help on this or workaround will be really appreciated, Kind regards, Saad

4 5

Question regarding the compatibility of Ubuntu 22.04 LTS
by 董智康 07 Jun '22

07 Jun '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’m using Ubuntu 22.04 LTS now. I would like to study Nektar++, but I’m not sure if my OS is eligible for Nektar++. If it’s true, how could I install it? Best, Zhikang Dong

2 2

Nektar Floquet Analysis
by Matt Duran 07 Jun '22

07 Jun '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. ******************* Hello Nektar users, I have been experiencing some issues running a floquet analysis in Nektar. I was wondering if anyone could send me some files I could use as an example. I have followed the userguide but still have had issues. If I could see some case files for example it would be very helpful. Thanks, Matt Duran

2 1

Cannot connect to cloud resources
by 董智康 30 May '22

30 May '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 connect to your cloud resources Jupyter notebook (the link from tutorial). But it seems like the server is not responded. I’m not sure if you close your cloud resources or there are some problems with my network. Thanks, Zhikang Dong

2 1