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Hi all,
When using the incompressible Navier-Stokes solver, is it possible to add
a force that is a function of spatial location, for example a localised
"ideal fan" momentum source in a specific region?
Could this force also be a function of time and/or of the momentum at a
(different) given point or region?
Kind Regards,
Kumi
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Hello Nektar users,
I would like to simulate a merging junction using the PulseWaveSolver but struggle to do so.
As a guide I used the Merging.xml file in PulseWaveSolver > Examples > Merging.xml, however the example is not a merging junction.
I confirmed this through the following print command in PulseWaveSystem.cpp which returns 0 (and 1 for bifurcations)
cout << "Number of merging junctions: " << m_mergingJcts.size() << std::endl;
So, I decided to start from scratch. I can construct any arbitrary network geometry with segments and bifurcations but not if I add a merging junction.
The reason my merging junction cannot converge is because P_Au becomes -nan
I have tried many different configurations but did not succeed hence I finally decided to reach out.
Do you have any suggestion for me or in the best case a minimal working example of a merging junction model.xml file?
Best wishes,
Kai
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Hello,
I am trying to use the "extract" module to sample some data on a boundary ID.
In standalone mode, the module works as intended but I am encountering segmentation fault while using it in FieldCovert checkpoints.
I am supplying the settings as a separate file and this is my setup:
<NEKTAR>
<FILTERS>
<FILTER TYPE="FieldConvert">
<PARAM NAME="OutputFile">session.fld</PARAM>
<PARAM NAME="OutputFrequency">2</PARAM>
<PARAM NAME="Modules">extract:bnd=1</PARAM>
</FILTER>
</FILTERS>
</NEKTAR>
Can someone please point out what 's wrong in this setup ?
Regards,
Ishan
PGR
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Hello,
Section "4.5.18 Mesh projection" of the user guide suggests that CAD
projection can be used to refine a linear mesh using STEP geometry. When I
tried to do this, NekMesh gave the warning:
"This module is designed for use with Star-CCM+ meshes only; it also requires that the star mesh was created in a certain way."
Does anyone know what this "certain way" involves? Are there some criteria
that, if satisfied, would allow linear meshes generated without using
Star-CCM+ to be refined using CAD projection?
Regards,
Kumi
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Hello everyone,
since NekMesh doesn't seem to like my 3D mesh generated with ICEM and Gmsh (see thread "NekMesh: Inconsistent triangular face orientation"), I tried creating it directly with NekMesh by using a mesh configuration file or mcf ("mesh_configuration_file.txt"). However, this doesn't properly work either when I activate the boundary layer refinement or blr feature. I attached all the necessary files converted to txt.
I provided the geometry as *.step ("cylinder_geom_step_file1.txt") to the mcf and it works without blr. As soon as I switch on blr it throws the following warning, aborting the volume meshing process:
Fatal : Level 0 assertion violation
not setup for curve bl refinement
[InputMCF] WARNING: Volume meshing has failed with message:
[InputMCF] WARNING: Level 0 assertion violation
not setup for curve bl refinement
[InputMCF] WARNING: The linear surface mesh be written as a manifold mesh
If I include all the domain boundaries except for the two side faces along the cylinder axis, i.e. writing <P PARAM="BndLayerSurfaces" VALUE="1,2,3,4,6,7,8,9" /> with 5 and 10 being the two side faces, it works. But obviously, I only need blr on the cylinder surface and not anywhere else.
In a second attempt I loaded the geometry into Gmsh first, defined all the physical groups ("geo_file.txt") and again exported as *.step ("cylinder_geom_step_file2.txt"). This doesn't work at all, neither with nor without blr activated in the mcf and produces the following warning before crashing entirely:
Fatal : Level 0 assertion violation
surface mesh connectivity error
[InputMCF] WARNING: Surface meshing has failed with message:
[InputMCF] WARNING: Level 0 assertion violation
surface mesh connectivity error
[InputMCF] WARNING: Any surfaces which were successfully meshed will be written as a manifold mesh.
[InputMCF] - Elapsed time: 4.78223s.
[OutputNekpp] Writing Nektar++ file 'CylReD3900_3D_G1.xml'
Fatal : Level 0 assertion violation
Connected edges do not share a vertex. Edges 2347, 2345
terminate called after throwing an instance of 'Nektar::ErrorUtil::NekError'
what(): Level 0 assertion violation
Connected edges do not share a vertex. Edges 2347, 2345
Any help is very mush appreciated.
All the best
Alex
Sicher versendet mit [Proton Mail](https://proton.me/).
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Hi all,
I am running an 2D incompressible Navier Stokes simulation with a
dimensionless setup and using the AerForces filter.
I am trying to reproduce results from the literature that use the drag
coefficient defined as Cd = 2*Fd/(rho*U*U*D), where Fd is the drag force
per unit of length and D is the diameter of a cylinder. I wish to know
whether the value exported to the file DragLift.fce is half the Cd as
defined previously or the Cd itself. I think it is the former, but I would
like a confirmation.
For reference, I am sending a snippet of the session xml file.
<SOLVERINFO>
<I PROPERTY="SolverType"
VALUE="VelocityCorrectionScheme" />
<I PROPERTY="EQTYPE"
VALUE="UnsteadyNavierStokes" />
<I PROPERTY="EvolutionOperator" VALUE="Nonlinear"
/>
<I PROPERTY="Projection" VALUE="Galerkin"
/>
<I PROPERTY="GlobalSysSoln"
VALUE="DirectStaticCond" />
<I PROPERTY="TimeIntegrationMethod" VALUE="IMEXOrder2"
/>
<I PROPERTY="Driver" VALUE="Standard"
/>
<I PROPERTY="SPECTRALHPDEALIASING" VALUE="True"
/>
</SOLVERINFO>
<PARAMETERS>
<P> TimeStep = 0.01 </P>
<P> FinTime = 20 </P>
<P> NumSteps = FinTime/TimeStep </P>
<P> IO_CheckSteps = NumSteps/20 </P>
<P> IO_InfoSteps = 5 </P>
<P> IO_FiltersInfoSteps = 100 </P>
<P> IO_CFLSteps = 10 </P>
<P> Re = 66 </P>
<P> Kinvis = 1/Re </P>
</PARAMETERS>
<FILTERS>
<FILTER TYPE="AeroForces">
<PARAM NAME="OutputFile"> DragLift </PARAM>
<PARAM NAME="OutputFrequency"> 5 </PARAM>
<PARAM NAME="Boundary"> B[3] </PARAM>
</FILTER>
--
Daniel Rubano B. Turci
D. Sc. Student at Universidade Federal Fluminense (UFF).
Laboratory of Thermal Sciences - LATERMO.
*Rua Passo da Pátria, 156, Bloco D, sala 302, Niterói. RJ - 24210-240,
Brazil.*
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Hello everybody,
I was wondering, if there is a way to calculate spatial two-point correlation functions such as
R_uu = < u(x,t) * u(x + r,t) >
within Nektar++. Here, "u" is a scalar function, such as streamwise velocity, "< >" denotes a temporal average and "r" is a spatial separation distance.
My first idea was to use the HistoryPoints Filter, hence tracking the scalar along a line for each time step and calculating R_uu during postprocessing. But maybe there exists a more efficient way using a combination of Nektar++ Filters/Functions?
I appreciate any help on the topic.
All the best
Alex
Sicher versendet mit [Proton Mail](https://proton.me/).
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Hello,
I am using the Acoustic solver to solve Linearized Euler Equations. I wish to use a sponge region in my setup.
I have gone through the user guide and test cases but I am unable to understand how the coefficients are actually being applied in the sponge region. If I refer to Sec 3.6.1 of the v5.5.0 user guide, it says that the coefficient's values can be defined using the variable "r" and this variable can be used to control the distance to the sponge region.
So, are we specifying the distance to the sponge region or, the values of coefficients in the sponge region ? If it's the former, does it mean that damping of waves will automatically be applied by Nektar++?
I set-up a very simple 1D initial-value problem where a Gaussian pulse placed at the centre of -100 <= x <= 100 travels in left-right direction. I set-up the evaluation of "r" as a linear increase from -0.2 to 0 from x=60 to x=100. I was expecting that the pulse in the right will completely vanish as it reaches x=100. This was however not the case. I assumed that the amplitude of the pressure pulse will be multiplied by the values from -0.2 to 0.
Can someone please provide some clarity on this ?
Regards,
Ishan
PGR
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Dear Sir/Madam,
I am PhD student at Concordia University and I want to use Nektar++ for an
FSI simulation. I installed Nektar++ and want to run CylFlow_HomoStrip.xml
case as a starting point however I got the following error:
"Required parameter 'HomStructModesZ' not specified in session".
I appreciate it if you can help me with this.
Best regards,
Mahdi Riazat
Thank you Guglielmo and Selman
I tried C0Projection method but I ended up with the following distribution:
[image: image.png]
As you see there is so much oscillation!
I wonder how smooth your results are with WSS.
syavash
On Mon, May 20, 2024 at 2:56 PM Vivarelli, Guglielmo A <
guglielmo.vivarelli12(a)imperial.ac.uk> wrote:
> Hi Syavash,
>
> Try:
>
> FieldConvert -m C0Projection test.xml test.fld test-C0Proj.fld
>
> Regards,
>
> Guglielmo
> ------------------------------
> *From:* Ehsan Asgari <eh.asgari(a)gmail.com>
> *Sent:* 20 May 2024 18:52
> *To:* Vivarelli, Guglielmo A <guglielmo.vivarelli12(a)imperial.ac.uk>
> *Subject:* Re: [Nektar-users] WSS taking too much time
>
> Thanks Guglielmo
>
> It worked!
> However, the result is not satisfactory. I have a smooth velocity field
> but the wall shear stress exhibits discontinuities, likely due to C1 issue.
> Could you suggest a remedy?
>
> syavash
>
>
>
>
> On Mon, May 20, 2024 at 1:50 PM Vivarelli, Guglielmo A <
> guglielmo.vivarelli12(a)imperial.ac.uk> wrote:
>
> Hi Syawash,
>
> Try:
>
> "mpirun -np *your_cores* FieldConvert -m wss:bnd=3 <mesh.xml>
> <session.xml> <time-averaged.fld> <time-averaged-wss.fld>"
>
> Regards,
>
> Guglielmo
> ------------------------------
> *From:* nektar-users-bounces(a)imperial.ac.uk <
> nektar-users-bounces(a)imperial.ac.uk> on behalf of Ehsan Asgari <
> eh.asgari(a)gmail.com>
> *Sent:* 20 May 2024 17:48
> *To:* nektar-users <nektar-users(a)imperial.ac.uk>
> *Subject:* [Nektar-users] WSS taking too much time
>
>
> This email from eh.asgari(a)gmail.com 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 trying to extract the wall shear stress for a 2.5-D case using the
> wss module:
>
> FieldConvert -m wss:bnd=3 <mesh.xml> <session.xml> <time-averaged.fld> <time-averaged-wss.fld>
>
> However, it is taking too much time to execute, more than 1 hour with no output.
>
> I noticed another report on this issue in the mail archive, not sure if my case has the same problem.
>
>
> I appreciate any help you can provide.
>
> syavash
>
>
>