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[snappyHexMesh] SnappyHexMesh problems

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Old   April 21, 2014, 23:20
Question SnappyHexMesh problems
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Wang Jianhua
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I am new to the OpenFoam and so does the Snappy. When I use the snappy to refine my mesh, here is the problem I got:
--> FOAM FATAL ERROR:
[1] cell 143882 of level 0 uses more than 8 points of equal or lower level
Points so far:8(1600 1601 1604 1605 1606 12690 12691 12692)
[1] From function hexRef8::setRefinement(const labelList&, polyTopoChange&) in file polyTopoChange/polyTopoChange/hexRef8.C at line 3500.
FOAM parallel run aborting
I don't how this happens and what can I do to solve this problem. So is there anyone who can help me find the reason? Looking forward to your kind request.
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Old   April 23, 2014, 03:47
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Simon Zhang
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Quote:
Originally Posted by sjtuwjh View Post
I am new to the OpenFoam and so does the Snappy. When I use the snappy to refine my mesh, here is the problem I got:
--> FOAM FATAL ERROR:
[1] cell 143882 of level 0 uses more than 8 points of equal or lower level
Points so far:8(1600 1601 1604 1605 1606 12690 12691 12692)
[1] From function hexRef8::setRefinement(const labelList&, polyTopoChange&) in file polyTopoChange/polyTopoChange/hexRef8.C at line 3500.
FOAM parallel run aborting
I don't how this happens and what can I do to solve this problem. So is there anyone who can help me find the reason? Looking forward to your kind request.
Hi Jianhua,

Please delete all the files under /constant/polyMesh except blockMeshDict, and then re-do the blockMesh and snappyHexMesh.

Regards,
Simon
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Old   May 23, 2014, 05:36
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eugenio l
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Hi everyone,

I keep having the same problem, especially when dealing with refinement level greater than 1. Deleting the file in ./constant/polyMesh doesn't help.

The cell whose referencing the error is always cell 1 of level 0

Code:
cell 1 of level 0 uses more than 8 points of equal or lower level
Points so far:8(1 2 6 7 26 27 31 32)
Thanks in advance for any useful help

Eugenio
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Old   July 1, 2016, 07:31
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Hi,
I supose that's a bit late to post this, but maybe it will help someone.
I had the same error when I used snappy with a previously created blockmesh with mergePatchPairs.
The first step is to visualize where is that problem cell, using paraview you can find out it.
And my solution was to do a smaller refinement box, in order to have a distance from that patch to the box, and also reduce a little bit the difference between the sizes of the blockmesh merged patches.
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Old   April 10, 2017, 10:14
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Quote:
Originally Posted by danielbanos10 View Post
Hi,
I supose that's a bit late to post this, but maybe it will help someone.
I had the same error when I used snappy with a previously created blockmesh with mergePatchPairs.
The first step is to visualize where is that problem cell, using paraview you can find out it.
And my solution was to do a smaller refinement box, in order to have a distance from that patch to the box, and also reduce a little bit the difference between the sizes of the blockmesh merged patches.
True!

I found out using a lower nCellsBetweenLevels (1 or 0 instead of 2) in the snappyHexMeshDict helps too (which has to do with the transition smoothness between the different levels of refinement).

Dave
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Old   November 25, 2020, 18:49
Default snappyHexMesh aborts if background mesh was refined without level transition cells
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Claudio Boezio
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I just got the same error while trying to snap a surface into a background mesh previously refined with refineMesh. At first I thought that snappyHexMesh was aborted because it intersected a polyhedron cell with mor than 8 vertices. Upon investigation of the reported cell I noticed though that the incriminated cell was a hexahedron and also on the opposite end of the mesh, thus far from being intersected by the surface to be snapped. I then ran only one refinement with refineMesh and snappyHexMesh worked without errors to my surprise.

I've been using topoSet and refineMesh twice in a row to get two levels of refinement. This left no buffer cells between the refinement levels and is the likely cause of the problem. I changed the first topoSetDict to select a slightly larger cellSet as to leave at least one cell between the two refinement levels and after that snappyHexMesh ran without errors.

Cheers, Claudio
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