problem with adding layer in SHM
Hello,
I am using SnappyHexMesh with OF 2.0.1 to study a simple 2D wing. In order to use SnappyHexMesh, it is in fact a 3D case with a thin "wind tunnel". But SnappyHexMesh doesn't succeed in adding several layers in the boundary layer,can anyone tell me what should i do for giving good layers near the airfoil. i use low Re number turbulence models and i need to have small layer distance near the airfoil surface. please help me. Regards. |
hi sm
i am actually working on a 2D case, have a look on the post nCellsBetweenLevels problem will keep you up date as soon avery thing works... LL |
s.m,
maybe you could use a newer version of OF? A lot has happened to snappyHexMesh since 2.0.1. If your virtual wind tunnel is very thin there is a risk that the problem will persist, though. Mads |
Hi s.m,
What you can do is add one layer with snappy and then add the rest of the layers running the application refineWallLayer. I solve the same problem as you doing this. Hope this helps. Best, David |
adding layer with refineWallLayer
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i did what you tell me, but my layers at the trailing edge got damaged as you see in the pictures in following: |
Hi s.m,
You added two layers at the beginning try adding only one. |
hello S.m.
did you try to play with feature angle? i had good results with feature angle= 10 ... hope it s help LL |
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thanks a lot for replying me:), would you please tell me more about feature angle in SHM, what is the difference between feature angle=10 and e.g. feature angle=180? |
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thanks a lot for replying me, i did what you tell me and these are the results, thanks agian David, the results makes me happy:) but i do not know why my trailing edge is deforming in this way!? |
Hi,
Are you sure that this is not a problem in the sapping? Run the castellated mesh and the snapping. See the results and then add the layers |
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it seems that my SHM doesn’t snapp well, my snapControls in my SHM is in the following: snapControls { //- Number of patch smoothing iterations before finding correspondence // to surface nSmoothPatch 3; //- Relative distance for points to be attracted by surface feature point // or edge. True distance is this factor times local // maximum edge length. tolerance 4.0; //- Number of mesh displacement relaxation iterations. nSolveIter 30; //- Maximum number of snapping relaxation iterations. Should stop // before upon reaching a correct mesh. nRelaxIter 5; //- Highly experimental and wip: number of feature edge snapping // iterations. Leave out altogether to disable. //nFeatureSnapIter 10; } would you please tell me how should i change the numbers of it's parameters for having a good trailing edge in my airfoil. thanks o lot:) p-s: the whole file of my SHM is : castellatedMesh true; snap true; addLayers true; geometry { airfoil.stl { type triSurfaceMesh; name airfoil; } refinementBox { type searchableBox; min (-1 -1 -1); max ( 5 1 1); } }; castellatedMeshControls { maxLocalCells 100000; // 2500000; maxGlobalCells 2000000; // 10000000; minRefinementCells 100; // 0; nCellsBetweenLevels 6; //8; features ( { file "airfoil.eMesh"; level 0; } ); { airfoil { level (4 4); } } resolveFeatureAngle 30; refinementRegions { refinementBox { mode inside; levels ((1e15 3)); } } locationInMesh (-0.5 -0.1 0); allowFreeStandingZoneFaces true; } snapControls { nSmoothPatch 3; tolerance 4.0; nSolveIter 30; nRelaxIter 5; //nFeatureSnapIter 10; } addLayersControls { relativeSizes true; layers { "airfoil.*" { nSurfaceLayers 1; } } expansionRatio 1.2; finalLayerThickness 0.6; minThickness 0.1; featureAngle 60; nRelaxIter 5; nSmoothSurfaceNormals 1; nSmoothNormals 3; nSmoothThickness 10; maxFaceThicknessRatio 0.5; maxThicknessToMedialRatio 0.3; minMedianAxisAngle 90; nBufferCellsNoExtrude 0; nLayerIter 50; } meshQualityControls { maxNonOrtho 45; maxBoundarySkewness 2; maxInternalSkewness 2; maxConcave 80; minVol 1e-13; minTetQuality 1e-30; minArea -1; minTwist 0.05; minDeterminant 0.001; minFaceWeight 0.05; minVolRatio 0.01; minTriangleTwist -1; nSmoothScale 4; errorReduction 0.75; } debug 0; mergeTolerance 1e-6; |
Hi s.m,
It looks that it was working because in the previous images the edge is well snapped. Try relaxing the meshQualityControls: maxNonOrtho 65; maxInternalSkewness 4; You can also play with the feature angle |
hi sm
sorry i gave you bad information, you should try to augment featureAngle up to 100 or even 355... i have made to try on a case it works fine hope it help LL |
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hi sm
here a exemple... the telling edge of my .stl file is 10 deg but featureAngle concern cells angles... it s a limit above witch layer are not include ... hope it help... |
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would you please put your SHM here?:) my turbulence models are LowRe number models so i have to have y+<1 for this purpose i use refineWallLayer Utility after running the SHM, but now it seems that the parameters of SHM are not consistent to each other so gain bad tarailing edge meshing. thanks. |
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hi foamers,
i have another setting for SHM parameters, and i get me the following trailing edge : |
hi sm
please try your shmDict with feature angle 150 instead of 60 as i can see //- When not to extrude surface. 0 is flat surface, 90 is when two faces // make straight angle. featureAngle 60 |
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i change my featureAngle to 150 as you said but i doesn't change at all, i have one airfoil with two different snappyHexMeshDict but none of them give me a right mesh at the trailing edge !! what should i do to have a better meshing on airfoil? |
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i set maxNonOrtho 65; maxInternalSkewness 4; and also featureAngle 150; as laurentL said me, the result is really nice as you see: Dear David would you please tell me more explanation about maxNonOrtho and maxInternalSkewness? |
Hi,
If you set restrictive parameters in the quality controls the quality of the mesh will be better but it will create more problems during the snapping |
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