2D-meshing in cfd

A subforum specific to the development of the OpenFoam-based workbenches ( Cfd https://github.com/qingfengxia/Cfd and CfdOF https://github.com/jaheyns/CfdOF )

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thschrader
Posts: 1457
Joined: Sat May 20, 2017 12:06 pm
Location: Germany

2D-meshing in cfd

Postby thschrader » Sun Jul 29, 2018 10:42 am

I tried to use 2D-meshing (gmsh) in cfd-wb.
Extract 2D-shape from body using facebinder-tool in arch-wb.
FEM-meshing works for 2D, but cfd gives back error
„For 2D meshing, two parallel 2D bounding planes must be present as boundary conditions in the CFD analysis object.“
Is there a special workflow?
system:
OS: Windows 10
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.18.14098 (Git)
Build type: Release
Branch: master
Hash: 0c33d00bfdf8270e7e5b33d792bf0ad9bbbfc819
Python version: 2.7.14
Qt version: 4.8.7
Coin version: 4.0.0a
OCC version: 7.2.0
Locale: German/Germany (de_DE)
model.JPG
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2D_gmsh_cfd.JPG
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oliveroxtoby
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Re: 2D-meshing in cfd

Postby oliveroxtoby » Mon Jul 30, 2018 6:14 am

thschrader wrote:
Sun Jul 29, 2018 10:42 am
I tried to use 2D-meshing (gmsh) in cfd-wb.
Extract 2D-shape from body using facebinder-tool in arch-wb.
FEM-meshing works for 2D, but cfd gives back error
„For 2D meshing, two parallel 2D bounding planes must be present as boundary conditions in the CFD analysis object.“
Is there a special workflow?
Yes - create a 3D shape, then assign the CFD boundary 'constraint/2D bounding plane' to the front and back surfaces (which must be parallel and planar). Then mesh as normal.
Please provide all the information requested in this post before reporting problems with CfdOF.
thschrader
Posts: 1457
Joined: Sat May 20, 2017 12:06 pm
Location: Germany

Re: 2D-meshing in cfd

Postby thschrader » Mon Jul 30, 2018 4:14 pm

oliveroxtoby wrote:
Mon Jul 30, 2018 6:14 am
Yes - create a 3D shape, then assign the CFD boundary 'constraint/2D bounding plane' to the front and back surfaces (which must be parallel and planar). Then mesh as normal.
Thanks for the tip, it works.
2D is a nice option, saves a lot of computing time.
The solver storms through the calculation...
2D_run.JPG
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julieng
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Re: 2D-meshing in cfd

Postby julieng » Sun Dec 16, 2018 10:43 am

Hello,

I add the bounding planes parrallel but I have always the error message telling that I am not using them.
Something to activate somewhere?

Image
[/img]


Best regards

Julien
julieng
Posts: 40
Joined: Sun Nov 25, 2018 8:57 pm

Re: 2D-meshing in cfd

Postby julieng » Sun Dec 16, 2018 12:43 pm

Image
Image
thschrader
Posts: 1457
Joined: Sat May 20, 2017 12:06 pm
Location: Germany

Re: 2D-meshing in cfd

Postby thschrader » Sun Dec 16, 2018 1:48 pm

julieng wrote:
Sun Dec 16, 2018 10:43 am
I add the bounding planes parrallel but I have always the error message telling that I am not using them.
Something to activate somewhere?
Put each 2D-bounding plane into a separate constraint-condition, see my file.
gmsh: works fine
cfmesh: meshing error at front-window
snappyhexmesh: gives allways a 3D-mesh (?) :o
VW_Beetle.FCStd
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OS: Windows 10
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.18.15399 (Git)
Build type: Release
Branch: master
Hash: 9683abfc36c3e9e94b9175428ec9491b869a6b97
Python version: 2.7.14
Qt version: 4.8.7
Coin version: 4.0.0a
OCC version: 7.2.0
Locale: German/Germany (de_DE)
2D_bounding_planes.JPG
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julieng
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Re: 2D-meshing in cfd

Postby julieng » Sun Dec 16, 2018 5:27 pm

Thank you, it works with gmsh but no boundary layers are avalaible with gmsh. Only refinement on surfaces but I don't see any change in the mesh when I use or not these feature.

Now I want to try to calculate the lift and drag force acting on a surface ... Seems difficult, I start with your post on the topic "computing forces:how to setup proper simulation" https://forum.freecadweb.org/viewtopic.php?f=37&t=26923.

How can do to calculate the force acting on the surface of the circle?
Image

I don't know exactly how to start, maybe the paraview documentation or some tutorial?

Best regards

Julien
thschrader
Posts: 1457
Joined: Sat May 20, 2017 12:06 pm
Location: Germany

Re: 2D-meshing in cfd

Postby thschrader » Sun Dec 16, 2018 6:19 pm

julieng wrote:
Sun Dec 16, 2018 5:27 pm
I don't know exactly how to start, maybe the paraview documentation or some tutorial?
Have a look at this tutorial please.
https://www.youtube.com/watch?v=J944HOj_4b0
julieng
Posts: 40
Joined: Sun Nov 25, 2018 8:57 pm

Re: 2D-meshing in cfd

Postby julieng » Sun Dec 16, 2018 9:34 pm

Thank you very much for your help.

I see also some add-on workbench on the forum.

Image

Is these tools are usefull for the post processing ?

I install the workbench DesignPhysics, but I don't know how to put it visible on the FreeCAD windows.

Best regards

Julien
thschrader
Posts: 1457
Joined: Sat May 20, 2017 12:06 pm
Location: Germany

Re: 2D-meshing in cfd

Postby thschrader » Sun Dec 16, 2018 11:04 pm

julieng wrote:
Sun Dec 16, 2018 9:34 pm
Is these tools are usefull for the post processing ?
No, for openfoam results definitly not. Designsphysics is the Freecad-GUI for the dualsphysics-solver,
which uses a particle-method (point cloud). It is mainly used for free surface flow.
Advantage: writing the point cloud (the "mesh) goes superfast, even with millions of points.
Disadvantage: you need a really fast machine...
But it is interesting and cool stuff. Have a look at the tutorials
https://www.youtube.com/watch?v=uQ_vVYTRZZk
https://www.youtube.com/watch?v=B8mP9E75D08
http://design.sphysics.org/
http://www.dual.sphysics.org/