こんにちは（@t_kun_kamakiri）(‘◇’)ゞ
本記事ではオープンCAEを使ってバスケットボールまわりの流れを解析するまでをまとめていきます。
最終的には以下のようになります。
バスケットボール周りの流れももう少しでできそうかなという進捗。
#OpenFOAM pic.twitter.com/WdSGRX4nGI— カマキリ🐲Python頑張る昆虫 (@t_kun_kamakiri) November 5, 2021
バスケットボールはシュートの際に1秒間に2回転ほどしているそうです。
味方にパスをするときはもっと高速で回転していると思いますが、果たして回転させるとどう違うのか考察をしていく心意気です(^^)
カマキリ
自宅で解析できる記事は他にも書いています。
その他の記事
モデル作成と勉強しながら、アウトプットのため記事にまとめていきます。
今後の予定
- 【回転するバスケットボールまわりの流れ(1)】FreeCADで作るバスケットボール
- 【回転するバスケットボールまわりの流れ(2)】OpenFOAMで無回転のバスケットボールまわりのメッシュ作成
- 【回転するバスケットボールまわりの流れ(3)】OpenFOAMで無回転のバスケットボールまわりの流れ
- 【回転するバスケットボールまわりの流れ(4)】OpenFOAMで回転のバスケットボールまわりのメッシュ作成
- 【回転するバスケットボールまわりの流れ(5)】OpenFOAMで回転するバスケットボールまわりの流れ
- 【回転するバスケットボールまわりの流れ(6)】OpenFOAMで並列化計算
- 【回転するバスケットボールまわりの流れ(7)】OpenFOAMで抗力と揚力の出力
- 【回転するバスケットボールまわりの流れ(8)】PythonスクリプトによるOpenFOAMの自動計算
頑張りますよ(‘ω’)ノ
使用環境
- Windows11
- FreeCAD：0.19
- OpenFOAM-v2012 (2012)ESI版
- Paraview：5.9.0
メッシュ作成の手順
こちらにメモ書きを記載しています。
今回は「/opt/OpenFOAM/OpenFOAM-v2012/tutorials/incompressible/simpleFoam/motorbike」のチュートリアルからコピーして使おうと思います。
ファイル構成は以下のようになっています。
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/mnt/c/work/openfoam/20211010_basketball_flow/002_mesh_create |--motorBike | |--0.orig | | |--U | | |--include | | | |--fixedInlet | | | |--frontBackUpperPatches | | | |--initialConditions | | |--k | | |--nut | | |--omega | | |--p | |--Allclean | |--Allrun | |--constant | | |--transportProperties | | |--triSurface | | | |--README | | |--turbulenceProperties | |--mesh1 | | |--Mesh.log | | |--a.foam | | |--constant | | | |--polyMesh | | | | |--boundary | | | | |--cellLevel | | | | |--cellZones | | | | |--faceZones | | | | |--faces | | | | |--level0Edge | | | | |--neighbour | | | | |--owner | | | | |--pointLevel | | | | |--pointZones | | | | |--points | | | | |--sets | | | | | |--addedCells | | | | | |--layerFaces | | | | |--surfaceIndex | | | |--transportProperties | | | |--triSurface | | | | |--README | | | | |--basketball.stl | | | | |--basketball_mm.stl | | | | |--internalWall-sphere.stl | | | | |--internalWall-sphere_mm.stl | | | |--turbulenceProperties | | |--sHM | | | |--0.orig | | | | |--U | | | | |--include | | | | | |--fixedInlet | | | | | |--frontBackUpperPatches | | | | | |--initialConditions | | | | |--k | | | | |--nut | | | | |--omega | | | | |--p | | | |--1 | | | | |--cellLevel | | | | |--pointLevel | | | | |--polyMesh | | | | | |--boundary | | | | | |--cellLevel | | | | | |--cellZones | | | | | |--faceZones | | | | | |--faces | | | | | |--level0Edge | | | | | |--neighbour | | | | | |--owner | | | | | |--pointLevel | | | | | |--pointZones | | | | | |--points | | | | | |--surfaceIndex | | | |--2 | | | | |--cellLevel | | | | |--pointLevel | | | | |--polyMesh | | | | | |--boundary | | | | | |--cellLevel | | | | | |--cellZones | | | | | |--faceZones | | | | | |--faces | | | | | |--level0Edge | | | | | |--neighbour | | | | | |--owner | | | | | |--pointLevel | | | | | |--pointZones | | | | | |--points | | | | | |--surfaceIndex | | | |--3 | | | | |--cellLevel | | | | |--nSurfaceLayers | | | | |--pointLevel | | | | |--polyMesh | | | | | |--boundary | | | | | |--cellLevel | | | | | |--cellZones | | | | | |--faceZones | | | | | |--faces | | | | | |--level0Edge | | | | | |--neighbour | | | | | |--owner | | | | | |--pointLevel | | | | | |--pointZones | | | | | |--points | | | | | |--sets | | | | | | |--addedCells | | | | | | |--layerFaces | | | | | |--surfaceIndex | | | | |--thickness | | | | |--thicknessFraction | | |--system | | | |--blockMeshDict | | | |--controlDict | | | |--cuttingPlane | | | |--decomposeParDict.6 | | | |--ensightWrite | | | |--forceCoeffs | | | |--fvSchemes | | | |--fvSolution | | | |--meshQualityDict | | | |--snappyHexMeshDict | | | |--streamLines | | | |--surfaceFeatureExtractDict | | | |--topoSetDict | | | |--wallBoundedStreamLines | |--mesh2 | | |--0.orig | | | |--U | | | |--include | | | | |--fixedInlet | | | | |--frontBackUpperPatches | | | | |--initialConditions | | | |--k | | | |--nut | | | |--omega | | | |--p | | |--constant | | | |--transportProperties | | | |--triSurface | | | | |--README | | | |--turbulenceProperties | | |--system | | | |--blockMeshDict | | | |--controlDict | | | |--cuttingPlane | | | |--decomposeParDict.6 | | | |--ensightWrite | | | |--forceCoeffs | | | |--fvSchemes | | | |--fvSolution | | | |--meshQualityDict | | | |--snappyHexMeshDict | | | |--streamLines | | | |--surfaceFeatureExtractDict | | | |--topoSetDict | | | |--wallBoundedStreamLines | |--system | | |--blockMeshDict | | |--controlDict | | |--cuttingPlane | | |--decomposeParDict.6 | | |--ensightWrite | | |--forceCoeffs | | |--fvSchemes | | |--fvSolution | | |--meshQualityDict | | |--snappyHexMeshDict | | |--streamLines | | |--surfaceFeatureExtractDict | | |--topoSetDict | | |--wallBoundedStreamLines |
「mesh1」と「mesh2」は後々使うため、メッシュ生成のためだけに自身で作ったフォルダです。今回は「mesh1」でメッシュを作ります。
メッシュ生成のファイル
OpenFOAMでメッシュ生成するには2つのファイルを編集して実行する必要があります。
- blockMesh
- snappyHexMesh
blockMesh
「system/blockMeshDict」のファイルを以下のように編集します。
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/*--------------------------------*- C++ -*----------------------------------*\ ========= | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox \\ / O peration | Website: https://openfoam.org \\ / A nd | Version: 8 \\/ M anipulation | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; object blockMeshDict; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // convertToMeters 1; vertices ( ( -0.20 -0.20 -0.20) //0 /400mm ( 0.60 -0.20 -0.20) //1 ( 0.60 0.20 -0.20) //2 ( -0.20 0.20 -0.20) //3 ( -0.20 -0.20 0.20) //4 ( 0.60 -0.20 0.20) //5 ( 0.60 0.20 0.20) //6 ( -0.20 0.20 0.20) //7 ); blocks ( hex (0 1 2 3 4 5 6 7) (160 80 80) simpleGrading (1 1 1) //1mesh_5mm ); edges ( ); boundary ( //patch x_min_1 { type patch; faces ((0 4 7 3)); } x_max_1 { type patch; faces ((1 2 6 5)); } y_min_1 { type symmetryPlane; faces ((0 1 5 4)); } y_max_1 { type symmetryPlane; faces ((3 7 6 2)); } z_min_1 { type symmetryPlane; faces ((0 3 2 1)); } z_max_1 { type symmetryPlane; faces ((4 5 6 7)); } ); // ************************************************************************* // |
blockMeshを実行することで以下のメッシュが生成されます。
簡易バスケットボールのモデルと重ねてみて大きさを確認します。
snappyHexMesh
「system/snappyHexMeshDict」のファイルを以下のように編集します。
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/*--------------------------------*- 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 { basketball { type triSurfaceMesh; file "basketball_mm.stl"; } refinementBox { type box; min (-0.1 -0.1 -0.1); max ( 0.3 0.1 0.1); } } // 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 2000000; // 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 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 ( ); // 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 { basketball { // Surface-wise min and max refinement level level (1 1); // Optional specification of patch type (default is wall). No // constraint types (cyclic, symmetry) etc. are allowed. // patchInfo // { // } } } // Resolve sharp angles resolveFeatureAngle 60; // 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 { // refinementBox // { // } } // 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 (0.5 0.0 0.0); // Inside point // 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 true; } // 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; //- 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 false; //- Use castellatedMeshControls::features (default = true) explicitFeatureSnap true; //- Detect points on multiple surfaces (only for explicitFeatureSnap) multiRegionFeatureSnap false; } // 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 { "basketball" { nSurfaceLayers 5; } } // 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 150; // At non-patched sides allow mesh to slip if extrusion direction makes // angle larger than slipFeatureAngle. slipFeatureAngle 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 50; } // Generic mesh quality settings. At any undoable phase these determine // where to undo. meshQualityControls { #include "meshQualityDict" // Advanced //- Number of error distribution iterations nSmoothScale 4; //- Amount to scale back displacement at error points errorReduction 0.75; } // Advanced // Write flags writeFlags ( scalarLevels layerSets layerFields // write volScalarField for layer coverage ); // Merge tolerance. Is fraction of overall bounding box of initial mesh. // Note: the write tolerance needs to be higher than this. mergeTolerance 1e-6; // ************************************************************************* // |
バスケットボールまわりは
作成したモデル
作成したモデルは実際に流体解析で使うのでご利用ください。
ダウンロード
OpenFOAMの歩き方 (技術の泉シリーズ（NextPublishing）)
川畑 真一
1,100円(11/22 19:32時点)
発売日: 2021/02/26
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