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[snappyHexMesh] Snappy: cell normal orientation on open surface |
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#1 |
New Member
Nolwenn
Join Date: Apr 2010
Posts: 26
Rep Power: 17 ![]() |
Hello everybody,
When i use snappyHexMesh on a surface which isn't a closed one I have a problem with cell normals orientation: it isn't uniform on the surface (kind of random between 1 or -1). Normals are well oriented on my .stl file. Do you know a way to harmonize cell normals orientation after meshing ? Or maybe SnappyHexMesh isn't confortable with open surface? |
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#2 |
Senior Member
Andrea Pasquali
Join Date: Sep 2009
Location: Germany
Posts: 142
Rep Power: 17 ![]() |
Hi Nolwenn,
I have the same problem, I'd like to have uniform cellNormal in some faceZones inside my volume. I tried renumberMesh but without complete success. Did you found a solution for your problem? Andrea
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Andrea Pasquali |
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#3 |
New Member
Nolwenn
Join Date: Apr 2010
Posts: 26
Rep Power: 17 ![]() |
Hello Andrea,
No, for the moment I didn't make any progress with this. Can you tell me if you find something interesting ? Cheers Nolwenn |
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#4 |
Senior Member
Andrea Pasquali
Join Date: Sep 2009
Location: Germany
Posts: 142
Rep Power: 17 ![]() |
You can see my problem in attached picture,
I'd like to calculate the mass flow rater throgh a faceZone. The problem is the cellNormal in Z direction are random! (In my starting .stl the normals are uniform). So if I calculate the mass flow rate with OF function sum(phi) I got error. I'm thinking to calculate it like sum(phi*sign(normal)). Do you know if the normal is exportable like a field? I can see it in paraview but I don't see anything in my time or constant directory (I think paraview elaborate it depending on nodes numbering) Andrea
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Andrea Pasquali |
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#5 |
Guest
Posts: n/a
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Hi,
I have the same problem. Did you ever find out how to reset the surface normals? Regards Stefanie |
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#6 |
New Member
Nolwenn
Join Date: Apr 2010
Posts: 26
Rep Power: 17 ![]() |
Hi,
Nothing new ... I extract the values from neighbours cells during post processing. Nolwenn |
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#7 |
New Member
Choi Hak Kyu
Join Date: Apr 2015
Posts: 12
Rep Power: 12 ![]() |
Also, I have same problem.
So, Does anyone know how to use surfaceOrient utility? |
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#8 |
New Member
Choi Hak Kyu
Join Date: Apr 2015
Posts: 12
Rep Power: 12 ![]() |
I solved this problem from surfaceOrient utility
surfaceOrient <surfaceFile> <visiblePoint> <output surface file> |
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#9 |
New Member
Choi Hak Kyu
Join Date: Apr 2015
Posts: 12
Rep Power: 12 ![]() |
I solved this problem from surfaceOrient utility
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#10 |
Senior Member
chandra shekhar pant
Join Date: Oct 2010
Posts: 220
Rep Power: 17 ![]() |
Hello,
Could you please help, what is the meaning of <visiblePoint> in your post, I am really finding it hard to use this utility. Any comment/suggestion would be a great help, thanks in advance. |
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#11 |
Senior Member
Yann
Join Date: Apr 2012
Location: France
Posts: 1,298
Rep Power: 30 ![]() ![]() |
Hi,
Does the documentation helps? https://www.openfoam.com/documentati...aceOrient.html Cheers, Yann |
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#12 |
Senior Member
chandra shekhar pant
Join Date: Oct 2010
Posts: 220
Rep Power: 17 ![]() |
Thanks Yann for your help, but could not figure out the
Code:
point The visible 'outside' point |
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#13 |
Senior Member
Yann
Join Date: Apr 2012
Location: France
Posts: 1,298
Rep Power: 30 ![]() ![]() |
Hi,
It's just a point outside of your geometry, used by the utility do define what is "outside" the geometry and orient the normals accordingly. So pretty much any coordinate not located inside your geometry will do. (You can set a point very far and that's it). Of course surfaceOrient will not work if your surface is not closed. Cheers, Yann |
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#14 |
Senior Member
chandra shekhar pant
Join Date: Oct 2010
Posts: 220
Rep Power: 17 ![]() |
Thanks a lot Yann for your help, so this point should be outside the "bounding box" or "geometry" without considering any orientation etc ? Sorry for the multiple posts and for being so naive. Thank you very much for your help.
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#15 |
Senior Member
Yann
Join Date: Apr 2012
Location: France
Posts: 1,298
Rep Power: 30 ![]() ![]() |
It should be anywhere outside the volume of your surface file. It's just a point coordinates so there is not any notion of orientation.
Once you give this point, surfaceOrient knows which side of the surface is "outside" and which is "inside" and it will set the face normals accordingly. Cheers, Yann |
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#16 |
Senior Member
chandra shekhar pant
Join Date: Oct 2010
Posts: 220
Rep Power: 17 ![]() |
Thanks a lot Yann, using your help and guidance I am able to use this utility and achieved the desired goal of proper orientation.
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#17 |
New Member
Join Date: Jul 2024
Posts: 5
Rep Power: 2 ![]() |
I saw that nobody posted an example on how exactly to use the surfaceOrient.
So here is one "surfaceOrient test.stl "(68.66 19.0 -38.81)" testOrient.stl", where test.stl and testOrient.stl are the input and output files respectively, with (68.66 19.0 -38.81) being the outside point. The quotation marks are important for the point. |
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Tags |
cell normals, snappyhexmesh |
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