|
[Sponsors] |
[snappyHexMesh] Rough leading-edge and trailing-edge after snapping |
|
LinkBack | Thread Tools | Search this Thread | Display Modes |
September 15, 2021, 15:29 |
Rough leading-edge and trailing-edge after snapping
|
#1 |
Member
Gabriel Felix
Join Date: May 2021
Location: Brazil
Posts: 35
Rep Power: 6 |
Hi folks,
I'm running a propeller case and I'm getting a rough mesh discretization on the body near the trailing-edge and leading-edge. Surface is bumpy and prismatic on these regions. Even using featureEdge refinement level 9, and refinementSurfaces level (9 10) i can't improve the rough leading- and trailing-edge. I have already tried to tune all the snapControls parameters without any success. The leading-edge and trailing-edge still rough. The leading-edge discretization is poor and more refinement is needed on this region, since the curvature is been represented as straight lines with some kinks (this highly affects pressure distribution on the region). The snappyHexMesh fails to snap the mesh in this regions. SHM also seems to fail when adding layers on these regions as well. I don't know what to do anymore. I was even thinking on user another mesh program. I've already tried: - Using a higher quality .stl - Increasing or decreasing refinement levels in featureEdge, refinementSurface - Changed nCellsBetweenLevels - Switched from implicitFeatureSnap to explicitFeatureSnap (improved a little) - Changed snap tolerance. Below 1.0 it worsen the mesh an above 1.0 it has no apparent effect - Tune every snapControls parameters - Changed meshQualityControls parameters - Changed minTetQuality to -1e30 (improved a little) - etc Below are some images, the link to download the case, snappyHexMeshDict and checkMesh output. Images 1 and 2 are the resultant solid after meshing Images 7 and 8 are the internal mesh slice Image 9 is the stl file My case is available here if anyone wants to try running it: https://drive.google.com/file/d/1xdq...ew?usp=sharing I suggest you to use the Allrun scripts. My snappyHexMeshDict: Code:
/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: v2012 | | \\ / A nd | Website: www.openfoam.com | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; object snappyHexMeshDict; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // // Which of the steps to run castellatedMesh true; snap true; addLayers true; // 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 { innerCylinderSmall.stl { type triSurfaceMesh; name innerCylinderSmall; } //innerCylinder.stl //{ // type triSurfaceMesh; // name innerCylinder; //} outerCylinder.stl { type triSurfaceMesh; name outerCylinder; } propellerTip.stl { type triSurfaceMesh; name propellerTip; } } // 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 500000; // 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 5000000; // 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 0; // 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 3; // 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 "innerCylinderSmall.eMesh"; level 5; } { file "outerCylinder.eMesh"; level 0; } { file "propellerTip.eMesh"; level 9; } ); // 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 { innerCylinderSmall { level (5 5); faceType boundary; cellZone innerCylinderSmall; faceZone innerCylinderSmall; cellZoneInside inside; } outerCylinder { level (0 0); } propellerTip { level (9 10); } } // Resolve sharp angles resolveFeatureAngle 30; // 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 { //innerCylinder //{ // mode inside; // levels ((1E15 5)); //} innerCylinderSmall { mode inside; levels ((1E15 6)); } } // 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 (0.01 -1.5 0.01); // 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 1.0; // 1.0; //- Number of mesh displacement relaxation iterations. nSolveIter 150; //- 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 30; // 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 { "propellerTip.*" { nSurfaceLayers 3; } } // 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 1.7.x! (didn't do anything in 1.7.x) 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 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 // Note: changed(corrected) w.r.t 1.7.x! 90 degrees corresponds to 130 // in 1.7.x. minMedialAxisAngle 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 4; 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 // to work. Set to very negative number (e.g. -1E30) to // disable. // <0 = inside out tet, // 0 = flat tet // 1 = regular tet minTetQuality -1e30; // 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; // ************************************************************************* // Code:
$ checkMesh /*---------------------------------------------------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: v2012 | | \\ / A nd | Website: www.openfoam.com | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ Build : _7bdb509494-20201222 OPENFOAM=2012 Arch : "LSB;label=32;scalar=64" Exec : checkMesh Date : Sep 15 2021 Time : 15:19:22 Host : MSI PID : 12237 I/O : uncollated Case : /mnt/c/Users/Felix/Documents/Mestrado/OpenFOAM/runs/mscPropeller/18mscSalomeAs14Compressible9-10newConfigsLayer nProcs : 1 trapFpe: Floating point exception trapping enabled (FOAM_SIGFPE). fileModificationChecking : Monitoring run-time modified files using timeStampMaster (fileModificationSkew 5, maxFileModificationPolls 20) allowSystemOperations : Allowing user-supplied system call operations // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // Create time Create mesh for time = 0 Time = 0 Mesh stats points: 1451811 faces: 3794952 internal faces: 3591866 cells: 1178648 faces per cell: 6.2672 boundary patches: 6 point zones: 0 face zones: 1 cell zones: 1 Overall number of cells of each type: hexahedra: 958645 prisms: 32238 wedges: 0 pyramids: 0 tet wedges: 224 tetrahedra: 0 polyhedra: 187541 Breakdown of polyhedra by number of faces: faces number of cells 4 11178 5 9382 6 26385 7 51150 8 13158 9 56525 10 160 11 60 12 14972 13 2 14 32 15 4387 17 12 18 138 Checking topology... Boundary definition OK. Cell to face addressing OK. Point usage OK. Upper triangular ordering OK. Face vertices OK. *Number of regions: 2 The mesh has multiple regions which are not connected by any face. <<Writing region information to "0/cellToRegion" <<Writing region 0 with 64413 cells to cellSet region0 <<Writing region 1 with 1114235 cells to cellSet region1 Checking patch topology for multiply connected surfaces... Patch Faces Points Surface topology outerCylinder 288 388 ok (non-closed singly connected) propellerTip 161714 174976 ok (closed singly connected) AMI1 20180 20350 ok (closed singly connected) AMI2 20720 20834 ok (closed singly connected) inlet 140 169 ok (non-closed singly connected) outlet 44 49 ok (non-closed singly connected) Checking faceZone topology for multiply connected surfaces... FaceZone Faces Points Surface topology innerCylinderSmall 40900 41184 ok (closed singly connected) Checking basic cellZone addressing... CellZone Cells Points VolumeBoundingBox innerCylinderSmall 1114235 1362647 0.297655 (-0.4375 -0.175161 -0.4375) (0.4375 0.325212 0.4375) Checking geometry... Overall domain bounding box (-1.04998 -2.45 -1.04998) (1.04998 1.05057 1.04998) Mesh has 3 geometric (non-empty/wedge) directions (1 1 1) Mesh has 3 solution (non-empty) directions (1 1 1) Boundary openness (2.11947e-18 2.03185e-17 -3.89911e-18) OK. Max cell openness = 4.22748e-16 OK. Max aspect ratio = 24.4339 OK. Minimum face area = 5.38589e-09. Maximum face area = 0.245378. Face area magnitudes OK. Min volume = 1.83686e-12. Max volume = 0.069149. Total volume = 11.9942. Cell volumes OK. Mesh non-orthogonality Max: 64.9066 average: 12.5906 Non-orthogonality check OK. Face pyramids OK. Max skewness = 3.98566 OK. Coupled point location match (average 0) OK. Mesh OK. End Last edited by gabrielfelix; September 16, 2021 at 08:57. |
|
September 16, 2021, 04:16 |
|
#2 |
Senior Member
Yann
Join Date: Apr 2012
Location: France
Posts: 1,222
Rep Power: 28 |
Hi Gabriel,
Here are my first thoughts:
Yann Last edited by Yann; September 16, 2021 at 07:01. |
|
September 16, 2021, 10:10 |
|
#3 | |
Member
Gabriel Felix
Join Date: May 2021
Location: Brazil
Posts: 35
Rep Power: 6 |
Hey Yann,
So I followed your tips and managed to improve the mesh. Here's what I did:
For those who didn't know the mean of the refinementSurfaces levels. I researched, and got from CFDSupport the following explanation: Quote:
Last edited by gabrielfelix; September 16, 2021 at 14:40. |
||
September 16, 2021, 11:42 |
|
#4 | |||
Senior Member
Yann
Join Date: Apr 2012
Location: France
Posts: 1,222
Rep Power: 28 |
Hi Gabriel,
Glad to see you are on your way to improve your mesh! Quote:
However, it might bring other issues: snappy often struggle to extrude layers on transitions between refinement levels. With bigger gap between the min and max refinement levels (e.g. (8 12)), you will also more refinement transitions zones hence more reasons for snappy to not extrude layers. A workaround could be to separate the leading edge, trailing edge and upper/lower surfaces of your airfoil in order to define specific refinement levels for each parts. Quote:
Quote:
Cheers, Yann |
||||
September 16, 2021, 16:17 |
|
#5 | ||
Member
Gabriel Felix
Join Date: May 2021
Location: Brazil
Posts: 35
Rep Power: 6 |
Quote:
I'm also getting a very large number of faces with face pyramid volume < 1e-13. 7496109 is pretty much the same number of my whole mesh cells. I think this is one of the reasons that SHM is taking so long to run. Code:
Checking mesh with layer ... Checking faces in error : non-orthogonality > 65 degrees : 114 faces with face pyramid volume < 1e-13 : 7496109 faces with concavity > 80 degrees : 0 faces with skewness > 4 (internal) or 4 (boundary) : 0 faces with interpolation weights (0..1) < 0.05 : 1326 faces with volume ratio of neighbour cells < 0.01 : 2 faces with face twist < 0.01 : 38 faces on cells with determinant < 0.001 : 0 Detected 7497589 illegal faces (concave, zero area or negative cell pyramid volume) Extruding 212139 out of 2157951 faces (9.83058%). Removed extrusion at 13521 faces. Added 629266 out of 6473853 cells (9.72012%). Quote:
I'll also separate the spinner and propeller inside the stl file to better control the refinement of the mesh around them. My mesh is becoming increasingly finer and the drawback is that I'm getting a finer mesh where I don't need it (on the spinner for exemple). Even my university cluster is strugling to run SHM on this high refinement levels, anything I can do to decrease cell number will be helpful. I really appreciate your help and support Yann! Your thoughts were immensely helpful to me. I was stuck on this rough mesh for a long time and your tips readily improved the mesh. Thanks for dedicating some of your time on helping the CFD community. |
|||
October 21, 2021, 10:41 |
|
#6 |
Member
Gabriel Felix
Join Date: May 2021
Location: Brazil
Posts: 35
Rep Power: 6 |
I would like to give some updates on the improvements I have had in my mesh after following some of the tips given here, specially by Yann.
Below are the new blockMesh and snappyHexMesh configs. blcokMeshDict Code:
FoamFile { version 2.0; format ascii; class dictionary; object blockMeshDict; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // scale 1; convertToMeters 1; vertices ( (-2.50 -2.50 -2.50) ( 2.50 -2.50 -2.50) ( 2.50 2.50 -2.50) (-2.50 2.50 -2.50) (-2.50 -2.50 2.50) ( 2.50 -2.50 2.50) ( 2.50 2.50 2.50) (-2.50 2.50 2.50) ); blocks ( hex (0 1 2 3 4 5 6 7) (12 20 12) simpleGrading (1 1 1) ); edges ( ); boundary ( walls { type wall; faces ( (2 6 5 1) (0 3 2 1) (0 4 7 3) (4 5 6 7) ); } inlet { type patch; faces ( (3 7 6 2) ); } outlet { type patch; faces ( (1 5 4 0) ); } ); // ************************************************************************* // Code:
FoamFile { version 2.0; format ascii; class dictionary; object snappyHexMeshDict; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // // Which of the steps to run castellatedMesh true; snap true; addLayers true; // 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 { innerCylinderSmall.stl { type triSurfaceMesh; name innerCylinderSmall; } //innerCylinder.stl //{ // type triSurfaceMesh; // name innerCylinder; //} outerCylinder.stl { type triSurfaceMesh; name outerCylinder; } propellerTip.stl { type triSurfaceMesh; name propellerTip; } propellerSpinner.stl { type triSurfaceMesh; name propellerSpinner; } } // 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 1000000; // 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 10000000; // 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 0; // 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 "innerCylinderSmall.eMesh"; level 2; } { file "outerCylinder.eMesh"; level 0; } { file "propellerTip.eMesh"; level 0; } { file "propellerSpinner.eMesh"; level 0; } ); // 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 { innerCylinderSmall { level (2 2); faceType boundary; cellZone innerCylinderSmall; faceZone innerCylinderSmall; cellZoneInside inside; } outerCylinder { level (0 0); } propellerTip { level (1 10); } propellerSpinner { level (1 6); } } // Resolve sharp angles resolveFeatureAngle 2.5; // Region-wise refinement // ~~~~~~~~~~~~~~~~~~~~~~ refinementRegions { //innerCylinder //{ // mode inside; // levels ((1E15 5)); //} innerCylinderSmall { mode inside; levels ((1E15 2)); } //outerCylinder //{ // mode inside; // levels ((1E15 1)); //} } // Mesh selection // ~~~~~~~~~~~~~~ locationInMesh (0.01 -1.5 0.01); // 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 2.0; // 1.0; //- Number of mesh displacement relaxation iterations. nSolveIter 100; //- 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 false; // Use castellatedMeshControls::features (default = true) explicitFeatureSnap true; // 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 { propellerTip { nSurfaceLayers 3; } //propellerSpinner // { // nSurfaceLayers 3; // } } // Expansion factor for layer mesh expansionRatio 1.1; // 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 1.7.x! (didn't do anything in 1.7.x) 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 1.7.x! 90 degrees corresponds to 130 // in 1.7.x. minMedialAxisAngle 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 100; } // 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 4; 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 -1e30; // 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; // ************************************************************************* // Another issue is that SHM continues to fail to add boundary layers properly on the whole airfoil surface, specially on the leading-edge. I think that I'll go for a 180 degrees mesh to reduce cell number and improve refinement. I'm getting heavy meshes with these configs and even my university cluster is taking hours to solve. cfMesh I felt like I was having the same old problems, but now with a more refined mesh. So I went after alternatives to SHM and found cfMesh which is an openFOAM module and is fully integrated to the OF environment. This video How to create your first mesh with cfMesh - tutorial by József Nagy helped me a lot with the introduction to cfMesh. It is a much simpler, more intuitive, increadibly fast, and requires fewer configurations compared to SHM. It really surprised me. I have started meshing with it and the very first mesh I came out with was better than any mesh I had done before with SHM. Not only the surface refinement was excelent, but it succesfully add layers on the whole propeller/airfoil surface. It also executed the mesh in less than a minute, when compared to 10-30 minutes of SHM. I found cfMesh really great, but I'm having difficulties to integrate the mesh to my structure and to dealing with some AMI patches that I still need to figure out as I discuss in this post: [cfMesh] Error when creating AMI patches propeller Mine cfMesh configs are below. I'm using cartesianMesh, which is composed by hex cells similar to SHM. meshDict Code:
FoamFile { version 2.0; format ascii; class dictionary; location "mesh"; object meshDict; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // surfaceFile "combined.fms"; minCellSize 0.005; maxCellSize 0.01; boundaryCellSize 0.05; localRefinement { "propellerTip" { //cellSize 0.000125; additionalRefinementLevels 6; } } surfaceMeshRefinement { innerCyl { surfaceFile "innerCylinderSmall.stl"; additionalRefinementLevels 1; } } boundaryLayers { //nLayers 3; thicknessRatio 1.1; maxFirstLayerThickness 0.5; patchBoundaryLayers { "propellerTip" { nLayers 3; allowDiscontinuity 0; } } } Attached are some images comparing the meshes Last edited by gabrielfelix; October 24, 2021 at 12:36. |
|
July 5, 2023, 21:57 |
|
#7 |
Member
Gabriel Felix
Join Date: May 2021
Location: Brazil
Posts: 35
Rep Power: 6 |
Hello guys, I finally found a solution to the problem and managed to mesh the propeller case with cfMesh succesfully. I posted the detailed solution in this thread.
[Guide] How to mesh a propeller domain using cfMesh - AMI patch Case files are also available. |
|
Tags |
leading edge, mesh, rough, snap, trailing edge |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Help with UDF for Hinged Leading and Trailing Edge Deflections | tsprengeler | FLUENT | 0 | August 12, 2021 15:59 |
Meshing near leading and trailing edge of propeller | surajp92 | STAR-CCM+ | 1 | June 1, 2017 02:40 |
Leading edge and trailing edge of an airfoil rotor blade | Jun_Milan | CFX | 0 | July 11, 2014 00:07 |
Y-Plus values at aerofoil leading edge and trailing edge at high incidence | Engr07 | Main CFD Forum | 4 | June 29, 2012 11:42 |
[DesignModeler] Creating a blunt trailing edge from collapsed leading edge | gmd | ANSYS Meshing & Geometry | 0 | March 2, 2012 10:48 |