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-   -   [snappyHexMesh] bad grid problem analysis (https://www.cfd-online.com/Forums/openfoam-meshing/220594-bad-grid-problem-analysis.html)

xwang252 September 13, 2019 03:35

bad grid problem analysis
 
3 Attachment(s)
I am using snappyHexMesh generating grid but it always has some very strange grid at the geometry surface. Can any expert tell the reason and solution? Thanks.

xwang252 September 14, 2019 00:48

grid problem
 
1 Attachment(s)
I used snappyHexMesh to generate mesh. I got this result as attached that the snap function cannnot capture the geometry (blue parts) accurately. Can any expert tell the reason and solution? Thanks.

xwang252 September 15, 2019 07:48

The problem can be solved in some degree by adjust the snap controls setting.

xwang252 September 15, 2019 07:52

grid problem
 
1 Attachment(s)
I encountered a new problem that grid at some corners of the geometry has been very weird. Can any expert tell the reason and solution?
Thanks

xwang252 September 15, 2019 07:53

Quote:

Originally Posted by xwang252 (Post 744716)
I encountered a new problem that grid at some corners of the geometry has been very weird. Can any expert tell the reason and solution?
Thanks

Even refining the grid near the geometry would not solve this problem.

xwang252 September 17, 2019 00:32

grid problem
 
3 Attachment(s)
I have finally fixed this problem.

it needs to be clarified that
SnappyHexMesh does has the capability to snap even sharp corners of the geometry. The key parameters for this problem are:
base mesh size
nCellsBetweenLevels - 6 //solve bad grids at STL surface
resolveFeatureAngle - 45 //value less than 90 could snap the perpendicular STL edge
features{*.eMesh} //solve bad/rounded grids at STL surface edge
refinementSurfaces{level(min,max)} //increase max value could help to snap edge more accurately in the same time keeping the STL surface grid size small
nSmoothPatch - 3 // setting this value a little bit larger help solve bad grid problem but not too large which would distort other good grids
nFeatureSnapIter - 5 //setting this value a little bit larger help solve bad grid problem but not too large which would increase iteration time significantly
explicitFeatureSnap - true //would help snap features


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