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[snappyHexMesh] Meshing a STL file which has holes

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Old   May 13, 2019, 03:21
Default Meshing a STL file which has holes
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Owais Shabbir
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Dear Forum people,

I am new to meshing on snappyHexMesh. Currently, I am trying to mesh a protecting case of batteries. It contains a lot holes of diameter 7mm.



I have tried changing the level of refinements and also a few other parameters to increase the refinement around the holes to achieve a circular refinement but as you can see the holes in the attached picture, they always have a non-circular shape.


I chose the snappyHexMeshDict file from the snappyMultiRegionHeater meshing tutorial and set the case according to my geometry.



Any help would be appreciated.
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Old   May 13, 2019, 08:47
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Hi!


It seems like if you loaded the castellated mesh not the snapped one.

Check how many timesteps do you have. If you have anything else not just a 0 folder, you have to check the last time in paraview or you will see the castellated mesh (by default 0 time is skipped). If you have this problem you can solve it by using the -overwrite switch in snappyHexMesh so you will overwrite your mesh at the 0 time.


If you don't have more timesteps, check if the snappying is enabled in the snappyHexMeshDict (at the begining of the file).
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Old   May 14, 2019, 07:33
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Owais Shabbir
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Hi,

I checked and it is turned on.
I am thinking maybe there is a new entity that I might have to introduce to refine the hole regions.
Btw just to clarify this is a solid present in the domain, I am meshing the flow domain around this solid.


This is the SHMDict that I am using, may be you can pick which entity should be improved/added.


Code:
            castellatedMesh   true;
   snap            true;
   addLayers       false;
   
   geometry
   {    topcover
       {
           type triSurfaceMesh;
           file "topcover.stl";
       }
   refinementBox   {type searchableBox; 
   min   (-0.02 -0.01 -0.01); 
   max   (0.7 0.03 0.2);}
   
   };
   
   castellatedMeshControls
   {
       maxLocalCells 500000;
       maxGlobalCells 5000000;
       minRefinementCells 10;
       nCellsBetweenLevels 3;
    features
       (
           {
               file "topcover.eMesh";
               level 4;
           }
       );
   
   
       refinementSurfaces
       {
           topcover
           {            level (5 5);
               faceZone topcover;
               cellZone topcover;
               cellZoneInside outside;
           }
     }
   
   
   
      resolveFeatureAngle 5;
       refinementRegions
       {
       //      refinementBox
       //     {
       //        mode inside;
        //       levels ((1E15 1));
           //}
       }
   
       locationInMesh (-0.1 -0.1 -0.25);
   
      allowFreeStandingZoneFaces true;
   }
   snapControls
   {
        nSmoothPatch 3;
       tolerance 4.0;
       nSolveIter 30;
       nRelaxIter 5;
       nFeatureSnapIter 15;
   
   implicitFeautureSnap        false;
   explicitFeatureSnap                true;
   multiRegionFeatureSnap        false;
   }
   
   addLayersControls
   {
       relativeSizes true;
       {
           topcover
           {
               nSurfaceLayers 3;
           }
       }
       expansionRatio 1.3;
       finalLayerThickness 0.02;
       minThickness 0.01;
       nGrow 1;
       featureAngle 80;
       nRelaxIter 3;
       nSmoothSurfaceNormals 1;
      nSmoothNormals 3;
       nSmoothThickness 2;
       maxFaceThicknessRatio 0.5;
       maxThicknessToMedialRatio 1;
       minMedianAxisAngle 90;
       nBufferCellsNoExtrude 0;
       nLayerIter 50;
   }
   
   meshQualityControls
   {
       #include "meshQualityDict"
   }
   
   ce   needs to be higher than this.
   mergeTolerance   1e-6;

I have removed the comments so it is clear and concise to be read.
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