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[snappyHexMesh] Mesh not updating after increasing refinement |
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#1 |
New Member
Santi Parera
Join Date: Jul 2019
Location: BARCELONA
Posts: 26
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Hey there,
I'm using snappyHexMesh in an AWS instance (using the CFDDFC command line interface) and after doing checkMeshs it seems the number of cells keeps to be the same. As this is a complicated 3D geometry I started with a not so high refinement level and controlled the mesh with maxGlobalCells. The method was, set 2000000 max cells and lower the refinement levels till it does not reach this max level. After that take a close look and see with what specific refinement type I had to go on and do the same. I reached 6000000 cells and still getting some errors in checkMesh, but all the parameters are getting better. Now I have raised the max to 6500000 and put a little more of refinement, but the results of ALL chechMesh data are EXACTLY the same than the previous. SnappyHexMesh log informs as the refining has reached the max level, but it has finished the meshing process properly. It also agrees with checkMesh with the statistics. How can the mesh be the same after increasing the max level and some refinements!! Thanks. |
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#2 |
New Member
Jack B
Join Date: Jul 2018
Posts: 11
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Hi Kalabagh,
Could you post your checkMesh, snappyHexMeshDict and your geometry to get a better idea of what's going on? Also It would be beneficial to check where these problem cells are by using the foamToVTK command. If I am not mistaken increasing the the refinement isn't necessarily going to fix all your problems. A bad input geometry or the wrong snappyHexMesh settings can be the issue but its hard to help without seeing the checkMesh output and snappyHexMeshDict. |
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#3 |
New Member
Santi Parera
Join Date: Jul 2019
Location: BARCELONA
Posts: 26
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The zip folder with the geometry and blockMesh exceeds the maximum, so here's the link: https://drive.google.com/file/d/1wm6...ew?usp=sharing
This is checkMesh for the 3rt mesh: Code:
Build : 8-340defec456f Exec : checkMesh -allGeometry -allTopology -writeSets vtk Date : May 05 2021 Time : 18:50:01 Host : "ip-172-31-27-198" PID : 8442 I/O : uncollated Case : /home/ubuntu/OXIRIS_REV nProcs : 1 sigFpe : Enabling floating point exception trapping (FOAM_SIGFPE). fileModificationChecking : Monitoring run-time modified files using timeStampMaster (fileModificationSkew 10) allowSystemOperations : Allowing user-supplied system call operations // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // Create time --> FOAM Warning : From function static Foam::instantList Foam::timeSelector::select0(Foam::Time&, const Foam::argList&) in file db/Time/timeSelector.C at line 269 No time specified or available, selecting 'constant' Create polyMesh for time = constant Enabling all (cell, face, edge, point) topology checks. Enabling all geometry checks. Reconstructing and writing vtk representation of all faceSets and cellSets. Time = constant Mesh stats points: 6515840 faces: 16161800 internal faces: 14760764 cells: 4860137 faces per cell: 6.36249 boundary patches: 4 point zones: 0 face zones: 1 cell zones: 3 Overall number of cells of each type: hexahedra: 3842957 prisms: 194516 wedges: 0 pyramids: 0 tet wedges: 2065 tetrahedra: 0 polyhedra: 820599 Breakdown of polyhedra by number of faces: faces number of cells 4 48696 5 60452 6 200339 7 3226 8 1273 9 354803 10 801 11 764 12 109374 13 121 14 397 15 34452 16 16 17 118 18 5757 21 10 Checking topology... Boundary definition OK. Cell to face addressing OK. Point usage OK. Upper triangular ordering OK. Face vertices OK. Topological cell zip-up check OK. <<Number of duplicate (not baffle) faces found: 7. This might indicate a problem. <<Number of faces with non-consecutive shared points: 8. This might indicate a problem. <<Writing 23 faces with non-standard edge connectivity to set edgeFaces <<Writing 4 cells with zero or one non-boundary face to set oneInternalFaceCells <<Writing 23 cells with two non-boundary faces to set twoInternalFacesCells *Number of regions: 2 The mesh has multiple regions which are not connected by any face. <<Writing region information to "constant/cellToRegion" <<Writing region 0 (fully disconnected) with 4566597 cells to cellSet region0 <<Writing region 1 (fully disconnected) with 293540 cells to cellSet region1 Checking patch topology for multiply connected surfaces... Patch Faces Points Surface topology Bounding box TURBINA 64402 69427 ok (closed singly connected) (-0.450157 -0.2275 -0.600122) (0.450157 4.1725 0.600122) REACTOR 1230010 1305069 ok (closed singly connected) (-0.964995 -0.9236 -0.963344) (0.959343 4.22713 0.963345) ROTOR 53555 57797 ok (closed singly connected) (-0.700728 -0.240026 -0.699433) (0.695518 4.18647 0.699128) ROTOR_slave 53069 57406 ok (closed singly connected) (-0.700003 -0.240562 -0.698775) (0.695267 4.18645 0.699006) Checking geometry... Overall domain bounding box (-0.964995 -0.9236 -0.963344) (0.959343 4.22713 0.963345) Mesh has 3 geometric (non-empty/wedge) directions (1 1 1) Mesh has 3 solution (non-empty) directions (1 1 1) Boundary openness (-4.84183e-16 -4.5411e-17 1.20272e-15) OK. Max cell openness = 4.18834e-16 OK. Max aspect ratio = 50.8108 OK. Minimum face area = 2.02074e-08. Maximum face area = 0.00893745. Face area magnitudes OK. Min volume = 4.33648e-09. Max volume = 0.000565624. Total volume = 12.8158. Cell volumes OK. Mesh non-orthogonality Max: 64.999 average: 15.7927 Non-orthogonality check OK. Face pyramids OK. ***Max skewness = 7.83481, 133 highly skew faces detected which may impair the quality of the results <<Writing 133 skew faces to set skewFaces Coupled point location match (average 0) OK. ***Error in face tets: 2562 faces with low quality or negative volume decomposition tets. <<Writing 2379 faces with low quality or negative volume decomposition tets to set lowQualityTetFaces Min/max edge length = 8.09615e-06 0.136443 OK. <<Writing 4 near (closer than 5.82625e-06 apart) points to set nearPoints *There are 33202 faces with concave angles between consecutive edges. Max concave angle = 79.9951 degrees. <<Writing 33202 faces with concave angles to set concaveFaces Face flatness (1 = flat, 0 = butterfly) : min = 0.0529411 average = 0.999035 *There are 938 faces with ratio between projected and actual area < 0.8 Minimum ratio (minimum flatness, maximum warpage) = 0.0529411 <<Writing 938 warped faces to set warpedFaces Cell determinant (wellposedness) : minimum: 0 average: 12.3539 ***Cells with small determinant (< 0.001) found, number of cells: 104 <<Writing 104 under-determined cells to set underdeterminedCells ***Concave cells (using face planes) found, number of cells: 358423 <<Writing 358423 concave cells to set concaveCells Face interpolation weight : minimum: 0.0500341 average: 0.455345 Face interpolation weight check OK. Face volume ratio : minimum: 0.0100194 average: 0.771984 Face volume ratio check OK. Failed 4 mesh checks. End Code:
/*---------------------------------------------------------------------------*\ ========= | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox \\ / O peration | Website: https://openfoam.org \\ / A nd | Version: 8 \\/ M anipulation | \*---------------------------------------------------------------------------*/ Build : 8-340defec456f Exec : checkMesh -allGeometry -allTopology -writeSets vtk Date : May 11 2021 Time : 18:53:51 Host : "ip-172-31-27-198" PID : 1175931 I/O : uncollated Case : /home/ubuntu/OXIRIS_REV nProcs : 1 sigFpe : Enabling floating point exception trapping (FOAM_SIGFPE). fileModificationChecking : Monitoring run-time modified files using timeStampMaster (fileModificationSkew 10) allowSystemOperations : Allowing user-supplied system call operations // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // Create time --> FOAM Warning : From function static Foam::instantList Foam::timeSelector::select0(Foam::Time&, const Foam::argList&) in file db/Time/timeSelector.C at line 269 No time specified or available, selecting 'constant' Create polyMesh for time = constant Enabling all (cell, face, edge, point) topology checks. Enabling all geometry checks. Reconstructing and writing vtk representation of all faceSets and cellSets. Time = constant Mesh stats points: 6515840 faces: 16161800 internal faces: 14760764 cells: 4860137 faces per cell: 6.36249 boundary patches: 4 point zones: 0 face zones: 1 cell zones: 3 Overall number of cells of each type: hexahedra: 3842957 prisms: 194516 wedges: 0 pyramids: 0 tet wedges: 2065 tetrahedra: 0 polyhedra: 820599 Breakdown of polyhedra by number of faces: faces number of cells 4 48696 5 60452 6 200339 7 3226 8 1273 9 354803 10 801 11 764 12 109374 13 121 14 397 15 34452 16 16 17 118 18 5757 21 10 Checking topology... Boundary definition OK. Cell to face addressing OK. Point usage OK. Upper triangular ordering OK. Face vertices OK. Topological cell zip-up check OK. <<Number of duplicate (not baffle) faces found: 7. This might indicate a problem. <<Number of faces with non-consecutive shared points: 8. This might indicate a problem. <<Writing 23 faces with non-standard edge connectivity to set edgeFaces <<Writing 4 cells with zero or one non-boundary face to set oneInternalFaceCells <<Writing 23 cells with two non-boundary faces to set twoInternalFacesCells *Number of regions: 2 The mesh has multiple regions which are not connected by any face. <<Writing region information to "constant/cellToRegion" <<Writing region 0 (fully disconnected) with 4566597 cells to cellSet region0 <<Writing region 1 (fully disconnected) with 293540 cells to cellSet region1 Checking patch topology for multiply connected surfaces... Patch Faces Points Surface topology Bounding box TURBINA 64402 69427 ok (closed singly connected) (-0.450157 -0.2275 -0.600122) (0.450157 4.1725 0.600122) REACTOR 1230010 1305069 ok (closed singly connected) (-0.964995 -0.9236 -0.963344) (0.959343 4.22713 0.963345) ROTOR 53555 57797 ok (closed singly connected) (-0.700728 -0.240026 -0.699433) (0.695518 4.18647 0.699128) ROTOR_slave 53069 57406 ok (closed singly connected) (-0.700003 -0.240562 -0.698775) (0.695267 4.18645 0.699006) Checking geometry... Overall domain bounding box (-0.964995 -0.9236 -0.963344) (0.959343 4.22713 0.963345) Mesh has 3 geometric (non-empty/wedge) directions (1 1 1) Mesh has 3 solution (non-empty) directions (1 1 1) Boundary openness (-4.84183e-16 -4.5411e-17 1.20272e-15) OK. Max cell openness = 4.18834e-16 OK. Max aspect ratio = 50.8108 OK. Minimum face area = 2.02074e-08. Maximum face area = 0.00893745. Face area magnitudes OK. Min volume = 4.33648e-09. Max volume = 0.000565624. Total volume = 12.8158. Cell volumes OK. Mesh non-orthogonality Max: 64.999 average: 15.7927 Non-orthogonality check OK. Face pyramids OK. ***Max skewness = 7.83481, 133 highly skew faces detected which may impair the quality of the results <<Writing 133 skew faces to set skewFaces Coupled point location match (average 0) OK. ***Error in face tets: 2562 faces with low quality or negative volume decomposition tets. <<Writing 2379 faces with low quality or negative volume decomposition tets to set lowQualityTetFaces Min/max edge length = 8.09615e-06 0.136443 OK. <<Writing 4 near (closer than 5.82625e-06 apart) points to set nearPoints *There are 33202 faces with concave angles between consecutive edges. Max concave angle = 79.9951 degrees. <<Writing 33202 faces with concave angles to set concaveFaces Face flatness (1 = flat, 0 = butterfly) : min = 0.0529411 average = 0.999035 *There are 938 faces with ratio between projected and actual area < 0.8 Minimum ratio (minimum flatness, maximum warpage) = 0.0529411 <<Writing 938 warped faces to set warpedFaces Cell determinant (wellposedness) : minimum: 0 average: 12.3539 ***Cells with small determinant (< 0.001) found, number of cells: 104 <<Writing 104 under-determined cells to set underdeterminedCells ***Concave cells (using face planes) found, number of cells: 358423 <<Writing 358423 concave cells to set concaveCells Face interpolation weight : minimum: 0.0500341 average: 0.455345 Face interpolation weight check OK. Face volume ratio : minimum: 0.0100194 average: 0.771984 Face volume ratio check OK. Failed 4 mesh checks. End |
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#4 |
New Member
Santi Parera
Join Date: Jul 2019
Location: BARCELONA
Posts: 26
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Also, here is the last snappyHexMesh log: https://drive.google.com/file/d/1wun...ew?usp=sharing
I've have been doing exactly what you say. With the vtk format I tried to search where the different wrong cells were and think what kind of refinement should be done. |
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#5 |
New Member
Santi Parera
Join Date: Jul 2019
Location: BARCELONA
Posts: 26
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Sorry,
The snnapyHexMeshDict: Code:
/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: 5 | | \\ / A nd | Web: www.OpenFOAM.org | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; object snappyHexMeshDict; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // // Which of the steps to run castellatedMesh true; snap true; addLayers false; // Geometry. Definition of all surfaces. All surfaces are of class // searchableSurface. // Surfaces are used // - to specify refinement for any mesh cell intersecting it // - to specify refinement for any mesh cell inside/outside/near // - to 'snap' the mesh boundary to the surface geometry { TURBINA { type triSurfaceMesh; file "TURBINA_SCALED.stl"; } REACTOR { type triSurfaceMesh; file "REACTOR_SCALED.stl"; } ROTOR { type triSurfaceMesh; file "ROTOR_SCALED.stl"; } }; // Settings for the castellatedMesh generation. castellatedMeshControls { // Refinement parameters // ~~~~~~~~~~~~~~~~~~~~~ // If local number of cells is >= maxLocalCells on any processor // switches from from refinement followed by balancing // (current method) to (weighted) balancing before refinement. maxLocalCells 100000; // Overall cell limit (approximately). Refinement will stop immediately // upon reaching this number so a refinement level might not complete. // Note that this is the number of cells before removing the part which // is not 'visible' from the keepPoint. The final number of cells might // actually be a lot less. maxGlobalCells 6500000;//6000000;//5000000;//4000000;//3500000;//3000000; // The surface refinement loop might spend lots of iterations refining just a // few cells. This setting will cause refinement to stop if <= minimumRefine // are selected for refinement. Note: it will at least do one iteration // (unless the number of cells to refine is 0) minRefinementCells 10; // Allow a certain level of imbalance during refining // (since balancing is quite expensive) // Expressed as fraction of perfect balance (= overall number of cells / // nProcs). 0=balance always. maxLoadUnbalance 0.10; // Number of buffer layers between different levels. // 1 means normal 2:1 refinement restriction, larger means slower // refinement. nCellsBetweenLevels 2; // Explicit feature edge refinement // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ // Specifies a level for any cell intersected by its edges. // This is a featureEdgeMesh, read from constant/triSurface for now. features ( { file "TURBINA_SCALED.eMesh"; level 4;//5; } { file "REACTOR_SCALED.eMesh"; level 3;//4; } { file "ROTOR_SCALED.eMesh"; level 0;//1; } ); // Surface based refinement // ~~~~~~~~~~~~~~~~~~~~~~~~ // Specifies two levels for every surface. The first is the minimum level, // every cell intersecting a surface gets refined up to the minimum level. // The second level is the maximum level. Cells that 'see' multiple // intersections where the intersections make an // angle > resolveFeatureAngle get refined up to the maximum level. refinementSurfaces { TURBINA { level (3 3);//(3 4);//(2 3); } REACTOR { level (3 4);//(2 3); } ROTOR { level (1 2);//(1 1); faceType boundary; cellZone ROTOR; faceZone ROTOR; cellZoneInside inside; } } // Resolve sharp angles resolveFeatureAngle 25;//20; // Region-wise refinement // ~~~~~~~~~~~~~~~~~~~~~~ // Specifies refinement level for cells in relation to a surface. One of // three modes // - distance. 'levels' specifies per distance to the surface the // wanted refinement level. The distances need to be specified in // descending order. // - inside. 'levels' is only one entry and only the level is used. All // cells inside the surface get refined up to the level. The surface // needs to be closed for this to be possible. // - outside. Same but cells outside. refinementRegions { REACTOR { mode inside; levels ((0 0)); } ROTOR { mode inside; levels ((0 1)); } } // Mesh selection // ~~~~~~~~~~~~~~ // After refinement patches get added for all refinementSurfaces and // all cells intersecting the surfaces get put into these patches. The // section reachable from the locationInMesh is kept. // NOTE: This point should never be on a face, always inside a cell, even // after refinement. locationInMesh (0.00 -0.50 0.00); // Whether any faceZones (as specified in the refinementSurfaces) // are only on the boundary of corresponding cellZones or also allow // free-standing zone faces. Not used if there are no faceZones. allowFreeStandingZoneFaces false; } // Settings for the snapping. 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; // 1.0; //- Number of mesh displacement relaxation iterations. nSolveIter 300; //- Maximum number of snapping relaxation iterations. Should stop // before upon reaching a correct mesh. nRelaxIter 5; // Feature snapping // Number of feature edge snapping iterations. // Leave out altogether to disable. nFeatureSnapIter 10; // Detect (geometric only) features by sampling the surface // (default=false). implicitFeatureSnap true; // Use castellatedMeshControls::features (default = true) explicitFeatureSnap false; // Detect features between multiple surfaces // (only for explicitFeatureSnap, default = false) multiRegionFeatureSnap true; } // Settings for the layer addition. 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 { } // Expansion factor for layer mesh expansionRatio 1.0; // Wanted thickness of final added cell layer. If multiple layers // is the thickness of the layer furthest away from the wall. // Relative to undistorted size of cell outside layer. // See relativeSizes parameter. finalLayerThickness 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 0.1; // 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. // Note: changed(corrected) w.r.t 17x! (didn't do anything in 17x) nGrow 0; // Advanced settings // When not to extrude surface. 0 is flat surface, 90 is when two faces // are perpendicular featureAngle 30; // Maximum number of snapping relaxation iterations. Should stop // before upon reaching a correct mesh. nRelaxIter 3; // 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 // Note: changed(corrected) w.r.t 17x! 90 degrees corresponds to 130 in 17x. 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; } // Generic mesh quality settings. At any undoable phase these determine // where to undo. meshQualityControls { //- Maximum non-orthogonality allowed. Set to 180 to disable. maxNonOrtho 65; //- Max skewness allowed. Set to <0 to disable. maxBoundarySkewness 20; maxInternalSkewness 4; //- Max concaveness allowed. Is angle (in degrees) below which concavity // is allowed. 0 is straight face, <0 would be convex face. // Set to 180 to disable. maxConcave 80; //- Minimum pyramid volume. Is absolute volume of cell pyramid. // Set to a sensible fraction of the smallest cell volume expected. // Set to very negative number (e.g. -1E30) to disable. minVol 1e-13; //- Minimum quality of the tet formed by the face-centre // and variable base point minimum decomposition triangles and // the cell centre. This has to be a positive number for tracking // to work. Set to very negative number (e.g. -1E30) to // disable. // <0 = inside out tet, // 0 = flat tet // 1 = regular tet minTetQuality -1; // 1e-30; //- Minimum face area. Set to <0 to disable. minArea -1; //- Minimum face twist. Set to <-1 to disable. dot product of face normal // and face centre triangles normal minTwist 0.01; //- Minimum normalised cell determinant // 1 = hex, <= 0 = folded or flattened illegal cell minDeterminant 0.001; //- minFaceWeight (0 -> 0.5) minFaceWeight 0.05; //- minVolRatio (0 -> 1) minVolRatio 0.01; //must be >0 for Fluent compatibility minTriangleTwist -1; // Advanced //- Number of error distribution iterations nSmoothScale 4; //- Amount to scale back displacement at error points errorReduction 0.75; // Optional : some meshing phases allow usage of relaxed rules. // See e.g. addLayersControls::nRelaxedIter. relaxed { //- Maximum non-orthogonality allowed. Set to 180 to disable. maxNonOrtho 75; } } // Merge tolerance. Is fraction of overall bounding box of initial mesh. // Note: the write tolerance needs to be higher than this. mergeTolerance 1e-6; // ************************************************************************* // |
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#6 |
New Member
Santi Parera
Join Date: Jul 2019
Location: BARCELONA
Posts: 26
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Hey Jack,
I have posted the information you required. Have you been able to take a look? Thanks. |
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Tags |
amount, cell, grow, number |
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