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SHM no layers added

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Old   May 8, 2014, 13:40
Default SHM no layers added
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M. C.
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Hi all,

I'm trying to add some layer to my geometry by using SHM, but no layers are added even if meshing process come to an end with no problem.

I managed to make a log file, but looking at it, I can't find any error that cause this.

I'm new to SHM (I started only few days ago), but I can0t figure out what's wrong.

I also upload my logfile and snappyHMDict.

Can you give me some hint?

Thanks a lot for any support.

Regards

Michele
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File Type: txt logSnappy.txt (46.4 KB, 8 views)
File Type: txt snappyHexMeshDict.txt (13.5 KB, 7 views)
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Old   May 9, 2014, 08:24
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Elo´se
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Hi Michele,
In lines 1223-1236 from your log, you can see that most of the layer cells do not satisfy the quality criterions. In that case, sHM delete the problematic cells, therefore removing all your layer cells from your mesh.
I see in your sHMdict that you have finalLayerThickness 0.001; which makes a very small size as it is relative to the outer cell size.
I'd first try to change finalLayerThickness to 0.5. If that doesn't help, try to insert 1 layer, then 2 layers,...
Good luck!
Elo´se
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Old   May 9, 2014, 17:40
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Thank you very much Elo´s, indeed I tryed to raise finalLayerthickness and I started to see layers addition, so I think I have to make some trial & error to get to a good mesh, and read more carefully log file.

Generally speaking, I have some question about SHM in order to understand the behavior of the mesher; keep in mind I'm a beginner on this, so following could seems trivial to an experienced user.

I think that every beginner start to play trial & error when he/she use SHM, but how to short learning curve?

According to your geometry shape and to the problem to solve, which step do you focus most to obtain a good mesh? (geometry, castellated, snapping, layer addiction, quality)

What parameters do you think have priority on a final mesh configurations?

Are there some of them that affect majorly final mesh, while other are only for refinements?

Some refinement option, can sometimes lead to a not good meshing process or even not obtain one? which are to be used carefully by you're experience?

Thanks in advance If you (or others) want to share use-experience.

Regards

Michele.
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Old   May 12, 2014, 06:51
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Quote:
Originally Posted by student666 View Post
I think that every beginner start to play trial & error when he/she use SHM, but how to short learning curve?
Start from some simple tutorial and go with increasing complexity.
Read those slides: http://openfoamwiki.net/images/f/f0/...SlidesOFW7.pdf
Understand one after another each of the sHM steps (castellation, snap, layers) by varying the parameters on some simple geometries
Search this section of the forum to learn from other user's experience
...
Quote:
Originally Posted by student666 View Post
According to your geometry shape and to the problem to solve, which step do you focus most to obtain a good mesh? (geometry, castellated, snapping, layer addiction, quality)
I consider each step as being important to obtain a final mesh of good quality. I use not to go for step i+1 as long as step i does not satisfy me.
Quote:
Originally Posted by student666 View Post
What parameters do you think have priority on a final mesh configurations? Are there some of them that affect majorly final mesh, while other are only for refinements?
I'm not sure I understand your question, but I'd say that the appropriate level of refinement must be used on each part of the geometry, that's an important start point.
Quote:
Originally Posted by student666 View Post
Some refinement option, can sometimes lead to a not good meshing process or even not obtain one? which are to be used carefully by you're experience?
By experience, each geometry/problem are different and you need to spend time to see what it is most sensitive to. I'm sorry not to be more specific here, but I might mislead you if I try

I hope those answers can help you, I'm sure that other users can complement!
Regards,
Elo´se
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Old   May 13, 2014, 14:44
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Very kind Eloise!

I think you gave good advice here, and useful link!

I think I can summarized by writing:" keep calm and start from the beginning"..."and grow slowly: be confident with what you're doing".

Yes! I agree with you; It's a question of time, but studying each timestep of the mesh generation to get to good result is the best way.

Thank you again for your support.

Regards.

Michele
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Old   May 15, 2014, 02:40
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Hi Eloise and Michele,

I have the same problem as Michele's one.

I have a main geometry in STL and additionally i separated the patches of this geometry in STL format to make my own boundaries.
( this is like a BOX in STL that i extracted front,back,inlet,outlet,... in STL separately)

but my question is the same as Micheleĺs.
no layer generates...

Please see my SHMdict and SHM.log and recommend me out of this issue.

Thanks in advance.

Metti
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File Type: txt SHMlog.txt (70.0 KB, 4 views)
File Type: txt snappyHexMeshDict.txt (13.6 KB, 5 views)
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Old   May 15, 2014, 03:16
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Hi Metti,
Your log says at line 1883 : No layers to generate ... So something must be wrong in the way you ask sHM to insert layers, because it understands that you don't want to add any layers.
I'd start by looking at the name of the patch on which you want to insert layers. Is the name walls_solid correct? You can check that by running checkMesh for example and see if this patch name exists. Or you can run foamToVTK on the mesh you generated and visualise the different existing patches.
I hope it helps you!
Regards,
Elo´se
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Old   May 15, 2014, 05:51
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Lots of Thanks Eloise,

you were right, something was mismatched.

but the main key point was what you've said about finalLayerThickness.
I'm so grateful of you that helped me with your comment & quick reply.

I'm working on it these days to get the most perfect mesh of my case.

If I encountered any problem, I'll be back to you.

thank you my friend.
Metti
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