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Dear sir
I am a PHD student from Tsinghua Univerity in China. I am writing this letter to enquire some questions about Nektar++ v5.2.0.
When the simulation about the VIV of a rigid cylinder are carried out by Nektar++, the Dis_y showed the same value in z direction. However, the Vel_y and Acel_y presented different values in z direction at the same time is quite different. It seems that the Vel_y and Acel_y should be the same value in the z direction for a rigid cylinder.
The results are presented as follow.
# Time z Disp_x Vel_x Acel_x Disp_y Vel_y Acel_y
400 0 0 0 0 0.00419954 -0.0018539027 -0.0046684539
400 0.19635 0 0 0 0.00419954 -0.0018539026 -0.0046731296
400 0.392699 0 0 0 0.00419954 -0.0018539025 -0.004678392
400 0.589049 0 0 0 0.00419954 -0.0018539025 -0.0046851524
400 0.785398 0 0 0 0.00419954 -0.0018539025 -0.0046888038
400 0.981748 0 0 0 0.00419954 -0.0018539025 -0.004685259
400 1.1781 0 0 0 0.00419954 -0.0018539026 -0.0046771037
400 1.37445 0 0 0 0.00419954 -0.0018539027 -0.00466885
400 1.5708 0 0 0 0.00419954 -0.0018539028 -0.0046617006
400 1.76715 0 0 0 0.00419954 -0.0018539029 -0.004654695
400 1.9635 0 0 0 0.00419954 -0.0018539029 -0.0046481107
400 2.15984 0 0 0 0.00419954 -0.001853903 -0.0046443416
400 2.35619 0 0 0 0.00419954 -0.001853903 -0.0046429716
400 2.55254 0 0 0 0.00419954 -0.0018539029 -0.0046455258
400 2.74889 0 0 0 0.00419954 -0.0018539029 -0.0046517606
400 2.94524 0 0 0 0.00419954 -0.0018539028 -0.0046603436
Thank you for your patient.
Best regards.
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Hi,
I think nektar++ can really benefit from using a "StartTime" for
writing the .chk files. Say that I want to generate several .chk during
a period of a vortex shedding. Right now I have two possibilities: (a)
start from initial conditions=0 which will generate a lot of
unnecessary .chk files because of the transient, or (b) run the
simulation (without writing any .chk) and then do a restart from the
.fld and write the .chk files. Because the transient will now be
shorter, the number of generated unnecessary .chk files will also be
smaller. In that sense, I think the Checkpoint fields filter could
implement some parameter to control the time step when to start writing
the chk files -- exactly the same (code) as for the aeroforces filter.
Cheers,
Guillermo
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Hi dear Nektar++ community.
I've been trying to obtain Graphicable files, so, I used the "FieldConvert test.xml test.fld test.dat" command to get readable data (ASCII).
Unfortunately, all I get is a confusing weird-looking file. Is there any other command to get ASCII data besides the FieldConvert command written above and that gives the data in a column-arrangement type format? I am using NCAR Graphics to draw my graphics.
Thanks for your time, any help is welcomed and highly appreciated.
Greetings, Octavio.
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Dear Nektar users and team,
Hello,
I have just started working with Nektar++. Currently, I'm trying to use the
Nektar++ to conduct global sensitivity analysis on the cylinder flow at
Re=100. The SFD base flow file is generated through the examples given in
*solvers/IncNavierStokesSolver/Tests/**Cyl_AdaptiveSFD.xml*. After that, I
change the session file according to the tutorials to get the direct and
adjoint modes. But I can only get the direct modes correctly. I don't know
whether there are some problems with my settings in the adjoint session
file (in the attachment).
Can anyone help me?
Looking forward to your reply!
Sincerely,
Sekar Verma
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Hello,
I am new to Nektar++, and have attempted to follow the tutorial on converting a Pointwise mesh to Nektar (nektar.info/mesh-conversion-from-gridgen-pointwise-to-nektar/), however when running NekMesh as indicated I get an error "No such module: Process: projectcad". I have Nektar++ version 5.3.0. Has this capability not yet been implemented? Thanks!
Andrew
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Hi dear Nektar++ community, I've been trying to execute the HistoryPoints filter but I'm still not getting the so called session.his file. This is the syntax I'm using:
*****************************************************************************************************************
<NEKTAR>
<FILTER TYPE="HistoryPoints">
<PARAM NAME="OutputFile">TimeValues</PARAM>
<PARAM NAME="OutputFrequency">1000</PARAM>
<PARAM NAME="Points">
1.3 0 0
1.5 0 0
0 0.5 0
0 -0.5 0
0.5 0.5 0
0.5 -0.5 0
</PARAM>
</FILTER>
</NEKTAR>
*****************************************************************************************************************
Thanks for your attention, any help is highly appreciated.
Kind regards, Octavio.
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Hello,
I am using CoupledLinearisedNS solver for 2D stabiblty analysis. To do this, it is needed to set the imaginary eigenvalue shift. Now it is possible only in 3D with a homogeneous direction.
I set an appropriate 3D case and the BetaZero property that overrides LHom.
As a result, eigenvalues look nice, but eigenfunctions are not. The eigenfunctions are not two-dimensional.
How I can get the eigenfunctions? Or my proposition about the BetaZero property is wrong?
Alex Proskurin
Altai state technical university
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Hello,
I am a beginner in Nektar++ and have compiled some of my questions below. I
would be glad if you can help.
1. Does IncNavierStokesSolver or any other solver support adaptive time
marching? It seems to me
that TimeStep, NumSteps, IO_CheckSteps, IO_InfoSteps, IO_CFLSteps are
required by the solver. I was wondering if it would be possible to control
the time step with e.g. a CFL number constraint? Then all IO_* (most
importantly CheckSteps) can be expressed in terms of simulation time (not
time step).
2. Is it possible to calculate the gradient of only one specific variable?
The gradient module calculates the gradients of all variables which
produces unnecessary data, slowing down post-processing and increasing the
size of the files. Is there a better way than calculating the gradient and
removing the unnecessary fields using removefield module?
3. Where can I find a use of the isocontours module of FieldConvert? I
couldn't figure out what kind of output it gives, and what it expects as
input.
4. Is it possible to map the results of a case to another where the meshes
are neither at same refinement level nor at the same order?
5. Is there a way to control solver tolerance? The standard residual level
allowed seems to be 1e-09, and how can I change it?
6. When visualising with ParaView (and also if you write a python script),
the best way I know is to convert the chk files into vtu files. In each of
those vtu files, the mesh is included, which increases its size. Is there a
way to use one mesh file (e.g. mesh.vtu or mesh.xml) and only convert the
variables to some other format? This would reduce the storage space needed
for a case. I would also appreciate it if you can suggest a totally new and
a better way of visualising the results.
7. In the mesh.xml file created by NekMesh, the NUMMODES of the expansions
are always 4, irrespective of the value of the ORDER parameter. Are those
just placeholders, or should I change them after meshing? In the session
file I set the NUMMODES as 1 + "the value of ORDER (in the mesh file)". Is
this the correct way?
8. When using AeroForces filter, can you change the formatting of the
output file? For example I want the time and the forces in scientific
format with 10 digits precision, how can I make this happen?
Thank you in advance for your help!
Best regards,
Ilteber
--
İlteber R. Özdemir
Dear all,
We are planning to hold the next Nektar++ workshop on the 13th-15th
September 2022 at Imperial College London. So please save the date!
We are finalising the exact timing of the event, but will put more
information online soon, including how to register. The event is planned
to be primarily an in-person meeting. However, we are, at a minimum,
aiming to accommodate viewing of the talks by remote attendees for those
unable to travel.
We look forward to seeing you in London in September.
Kind regards,
Chris
--
Chris Cantwell
Senior Lecturer in Aeronautics
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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Hello.
I am Dr Subhasisa Rath from Technion - Israel Institute of Technology. I would like to install nektar++ on my Ubuntu 22.04 OS.
I am not able to find any source-code for this OS.
May I know whether I can install or not on OS?
Best,
Subhasisa