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Old   February 7, 2014, 10:47
Default snappyHexMesh corners missing
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Hello,

I am using snappyHexMesh to mesh a box. However, I found that the corner (90 degree perpendicular) is missing after meshing.

I don't know why and how to avoid it.

Thanks for any replies.
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Old   February 10, 2014, 05:05
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Hi,
how did you create that box? With an .stl file or by refinementBox?
Have a look at this it is a nice tutorial for easy cases.
https://sites.google.com/site/snappy...ppyhexmeshdict
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Old   February 10, 2014, 05:51
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Quote:
Originally Posted by gelbebanane View Post
Hi,
how did you create that box? With an .stl file or by refinementBox?
Have a look at this it is a nice tutorial for easy cases.
https://sites.google.com/site/snappy...ppyhexmeshdict
With an STL.
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Old   February 10, 2014, 05:53
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Quote:
Originally Posted by gelbebanane View Post
Hi,
how did you create that box? With an .stl file or by refinementBox?
Have a look at this it is a nice tutorial for easy cases.
https://sites.google.com/site/snappy...ppyhexmeshdict
Thanks quite a lot. The link is quite useful to me.
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Old   February 10, 2014, 06:18
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Quote:
Originally Posted by gelbebanane View Post
Hi,
how did you create that box? With an .stl file or by refinementBox?
Have a look at this it is a nice tutorial for easy cases.
https://sites.google.com/site/snappy...ppyhexmeshdict
I read a sentence 'snappy doesn't work well with sharp edges' and I guess this is the reason why the corners of my box are missing.
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Old   February 10, 2014, 06:34
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Try to switch off the snap process like suggested in the tutorial.
I have also quiet a lot problems with sharp edges. You can also play with the implicit and explicit featureExtract option as well as with the tool "surfaceFeatureExtract"
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Old   February 11, 2014, 16:44
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Quote:
Originally Posted by gelbebanane View Post
Try to switch off the snap process like suggested in the tutorial.
I have also quiet a lot problems with sharp edges. You can also play with the implicit and explicit featureExtract option as well as with the tool "surfaceFeatureExtract"
Thank you.

I switched off snap and the corners of the box are kept.

However, if I do want to snap, what should I do?

Should I play around 'resolveFeatuerAngle'? Should I increase it or decrease it? Is it the smaller the better or otherwise?
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Old   February 11, 2014, 17:49
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Quote:
Originally Posted by gelbebanane View Post
Try to switch off the snap process like suggested in the tutorial.
I have also quiet a lot problems with sharp edges. You can also play with the implicit and explicit featureExtract option as well as with the tool "surfaceFeatureExtract"
Does 'explicit featureExtract' really help, since it is a problem of snapping and the geometry is simple and easy for sHM to implicitly find the feature edge?

What do you think?

Thanks a lot.
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Old   February 11, 2014, 18:32
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The "surfaceFeatureExtract" should help snappy to find the edges. But i am also not such an advanced user that i can tell you what will help you to get it right as well with no files from you.
Try to change the options in the snap subdirectory of the dict file.

To start, you can copy the snappyHexMeshDict from the "flange" tutorial (OF-install patch/tutorials/mesh/snappyHexMesh/flange) to your case and change the basic parameters like stl file and region names.

When you do not achieve any approvements it would be great when you can give the community the possibility to have a look at your case as well as at your snappyHexMeshDict file. A small description of your geometry or the stl file would also be very nice.

Good Night.
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Old   February 11, 2014, 19:26
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Quote:
Originally Posted by gelbebanane View Post
The "surfaceFeatureExtract" should help snappy to find the edges. But i am also not such an advanced user that i can tell you what will help you to get it right as well with no files from you.
Try to change the options in the snap subdirectory of the dict file.

To start, you can copy the snappyHexMeshDict from the "flange" tutorial (OF-install patch/tutorials/mesh/snappyHexMesh/flange) to your case and change the basic parameters like stl file and region names.

When you do not achieve any approvements it would be great when you can give the community the possibility to have a look at your case as well as at your snappyHexMeshDict file. A small description of your geometry or the stl file would also be very nice.

Good Night.
Thanks.

My geometry is rather simple: a box 3.1*3.1*2.5 and my STL is written by myself by using 8 vertices. I don't think there exist problems with my STL file.

For blockMeshDict, I also define the same 8 vertices and then use them to define the block.

From the flange case, it seems helpful by using explicit feature extraction. However, since sHM 2.2.2 has already supported implicit feature extraction, I guess we can also achieve success by using implicit settings. Therefore I am asking how to set 'resolveFeatureAngle', which is related to implicit feature extraction.
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