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[snappyHexMesh] Can' get stl patch name for addLayers right? |
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January 2, 2012, 08:10 |
Can' get stl patch name for addLayers right?
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#1 |
Senior Member
Klaus
Join Date: Mar 2009
Posts: 250
Rep Power: 22 |
Hello,
I need to add layers to my wing boundary to ultimately resolve the boundary layer. So far I was not able to get the patch name of the wing (wing.stl with the name wing) right so no layers were added. I know other people ran into the same problem but I couldn't find an answer. How is this name defined? What's the correct syntax in the snappyHexMeshDict? Here the relevant sections of snappyHexMeshDict: addLayers true; // true; ... geometry { wing.stl { type triSurfaceMesh; name wing; regions { wing { name wing; } } } ... // Settings for the layer addition. addLayersControls { relativeSizes true; layers { wing { nSurfaceLayers 3; } } Klaus |
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January 2, 2012, 09:25 |
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#2 |
Senior Member
Niels Nielsen
Join Date: Mar 2009
Location: NJ - Denmark
Posts: 555
Rep Power: 27 |
Disable layers and note the name of the patches of the output.
It will probably be wing_solid. If you open the stl file the first line will read. solid some_name_here If some_name_here is empty snappy will add _solid to the patch name. If some_name_here is present snappy will add _some_name_here to the patch name. This is the name you have to use for the layers. So its the name of the final output patch, not geometry!
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Linnemann PS. I do not do personal support, so please post in the forums. |
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January 2, 2012, 09:59 |
Name is right but no layers added?!
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#3 |
Senior Member
Klaus
Join Date: Mar 2009
Posts: 250
Rep Power: 22 |
Thank you for your feedback,
in my case even so the name defined in the stl file is wing (solid wing ...), the patch name accepted by OpenFoam is just wing - fixed. Nevertheless, the problems remains, no layers are added - see attached picture, snappyHexMeshDict and log file. What's wrong? Klaus |
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January 2, 2012, 18:31 |
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#4 |
New Member
anonymous
Join Date: Jan 2012
Posts: 7
Rep Power: 14 |
Most likely it will work when you change the layers definition entry
wing in line 208 of your sHMdict into wing_solid If there is no specific region name specified in the STL then automatically the created patch will get "_solid" at the end of the patch name. |
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January 2, 2012, 18:48 |
There IS a specific region name in the stl file!
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#5 |
Senior Member
Klaus
Join Date: Mar 2009
Posts: 250
Rep Power: 22 |
Hello,
There IS a specific region name in the stl file! It's wing (first line in the file is: solid wing) I am aware of the naming in the first line of stl files. That's why I am struggling with the error identification. Klaus |
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January 3, 2012, 05:53 |
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#6 |
New Member
Stefan
Join Date: Nov 2011
Posts: 4
Rep Power: 14 |
Hi Klaus,
do you work with ascii or binary stl file? You can change the name in the ascii file. In my case its: solid part --- endsolid part You have to define this name in the sHMDict: nameofstl_part But i have the same problems with the layers (see pictures) I changed these values again and again. Code:
finalLayerThickness 1;//0.3 //- Minimum thickness of cell layer. If for any reason layer // cannot be above minThickness do not add layer. // Relative to undistorted size of cell outside layer. minThickness 0.5; //0.1 |
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January 3, 2012, 05:55 |
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#7 |
New Member
anonymous
Join Date: Jan 2012
Posts: 7
Rep Power: 14 |
Check the log. Here the names of the patches are documented.
In your case it might be now :"wing_wing" |
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January 3, 2012, 06:28 |
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#8 |
Senior Member
Niels Nielsen
Join Date: Mar 2009
Location: NJ - Denmark
Posts: 555
Rep Power: 27 |
Hi Again
When you do the regions thing in the snappyDict it does not add _name to the patch name. Try and change the geometry section to this instead Code:
geometry { wing.stl { type triSurfaceMesh; regions { wing { name wing; } } } If this does not work its not a naming issue, but some settings. If you want/can share the case using maybe a public dropbox link. EDIT. on a side note you have set relativeSizes true; and the finalLayerThickness 0.002; If relative is set to true its relative to the first cell height as I recall. So 0.002 relative to the first cell height which is already small might get you below the tolerance and it will skip adding the layer. what happens if you use the settings from the SHM flange tutorial? just paste this in I've changed the names. Code:
addLayersControls { // Are the thickness parameters below relative to the undistorted // size of the refined cell outside layer (true) or absolute sizes (false). relativeSizes true; // Per final patch (so not geometry!) the layer information layers { "wing.*" { nSurfaceLayers 3; } } // Expansion factor for layer mesh expansionRatio 1.2; //- Wanted thickness of final added cell layer. If multiple layers // is the thickness of the layer furthest away from the wall. // See relativeSizes parameter. finalLayerThickness 0.3; //- Minimum thickness of cell layer. If for any reason layer // cannot be above minThickness do not add layer. // See relativeSizes parameter. minThickness 0.25; //- If points get not extruded do nGrow layers of connected faces that are // also not grown. This helps convergence of the layer addition process // close to features. nGrow 0; // Advanced settings //- When not to extrude surface. 0 is flat surface, 90 is when two faces // make straight angle. featureAngle 30; //- Maximum number of snapping relaxation iterations. Should stop // before upon reaching a correct mesh. nRelaxIter 5; // Number of smoothing iterations of surface normals nSmoothSurfaceNormals 1; // Number of smoothing iterations of interior mesh movement direction nSmoothNormals 3; // Smooth layer thickness over surface patches nSmoothThickness 10; // Stop layer growth on highly warped cells maxFaceThicknessRatio 0.5; // Reduce layer growth where ratio thickness to medial // distance is large maxThicknessToMedialRatio 0.3; // Angle used to pick up medial axis points minMedianAxisAngle 90; // Create buffer region for new layer terminations nBufferCellsNoExtrude 0; // Overall max number of layer addition iterations. The mesher will exit // if it reaches this number of iterations; possibly with an illegal // mesh. nLayerIter 50; // Max number of iterations after which relaxed meshQuality controls // get used. Up to nRelaxIter it uses the settings in meshQualityControls, // after nRelaxIter it uses the values in meshQualityControls::relaxed. nRelaxedIter 20; } Best
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Linnemann PS. I do not do personal support, so please post in the forums. |
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