snappyHexMesh & Mesh around a missile
 

Hi Dear Foamers,

These days, I am trying to create a good mesh (C-type) around a missile by using snappyhexmesh. Actually, geometry of the missile is similar to picture3. After creating mesh, boundary of the missile got a bad shape (similar to picture1). I should say that whole the mesh is similar to picture2. Could anyone help me to create a good mesh around the missile?

I appreciate your help.
Thanks and best regards,
Sasan.

P.S. Honestly, I used solidworks for creating the geometry and afterwards I imported the geometry in salome for specifying names of the boundaries and after that I exported 3 .stl files and I converted them to 1 .stl file by using cat name.stl >> assemble.stl .
I uploaded my case :
https://mega.co.nz/#!NlYFXDhD!bYtW2A...WNgA02EeYERHrE

snappyHexMeshDict :

I would give two recommendations:

1. Use OpenFOAM-2.3.x. OpenCFD is constantly patching snappyHexMesh.

2. Increase the min and max refinement level for the patch of interest like this or higher:

Good luck!


Cheers,
Kyle

I am trying to mesh a cylinder of 2 radius (cone+ cylinder).I don't know the reason, but I can't creat a layer to remove the bad sector. Picture and snappyHexMeshDic is given here. if anybody can suggest something .........

FoamFile
{
version 2.0;
format ascii;
class dictionary;
object snappyHexMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

// Which of the steps to run
castellatedMesh true; // make basic mesh ?
snap true; // decide to snap back to surface ?
addLayers true;//false; // decide to add viscous layers ?


geometry // Load in STL files here
{
inlet_1.stl {type triSurfaceMesh; name inlet_1;}
outlet.stl {type triSurfaceMesh; name outlet;}
inlet_2.stl {type triSurfaceMesh; name inlet_2;}
inlet_3.stl {type triSurfaceMesh; name inlet_3;}
wall.stl {type triSurfaceMesh; name wall;}
//cylinder.stl {type triSurfaceMesh; name volume;}
refineCylinder {type searchableCylinder; point1 (0 0 0); point2 (0 0 2); radius 0.13;}
//refinementBox {type searchableBox; min (-0.5 -0.5 -0.5); max ( 0.5 0.5 0.5);}
};

castellatedMeshControls
{
maxLocalCells 1000000; //max cells per CPU core
maxGlobalCells 2000000; //max cells to use before mesh deletion step
minRefinementCells 10; //was 0 - zero means no bad cells are allowed during refinement stages
maxLoadUnbalance 0.10;
nCellsBetweenLevels 1; // expansion factor between each high & low refinement zone

// Explicit feature edge refinement
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

features // taken from STL from each .eMesh file created by "SurfaceFeatureExtract" command
(
{file "inlet_1.eMesh"; level 2;}
{file "outlet.eMesh"; level 2;}
{file "wall.eMesh"; level 3;}
{file "inlet_2.eMesh"; level 2;}
{file "inlet_3.eMesh"; level 2;}
);

// Surface based refinement
// ~~~~~~~~~~~~~~~~~~~~~~~~

refinementSurfaces // Surface-wise min and max refinement level
{
inlet_1 {level (2 2);}
outlet {level (2 2);}
wall {level (5 5);}
inlet_2 {level (2 2);} // was 4 4
inlet_3 {level (2 2);} // was 4 4
}


resolveFeatureAngle 80; // Resolve sharp angles // Default 30
refinementRegions // In descending levels of fine-ness
{refineCylinder {mode distance; levels ((1E15 2));}} // (0.002 3) (0.01 2));}} // was ((0.001 4) (0.003 3) (0.01 2))
locationInMesh (0.01 0.01 0.01); //to decide which side of mesh to keep **
allowFreeStandingZoneFaces true;
}


// Settings for the snapping.
snapControls
{
nSmoothPatch 3;
tolerance 4.0;
nSolveIter 30;
nRelaxIter 5;
nFeatureSnapIter 15; // default is 10

// New settings from openfoam 2.2 onwards for SHMesh

implicitFeatureSnap false; // default is false - detects without doing surfaceFeatureExtract
explicitFeatureSnap true; // default is true
multiRegionFeatureSnap false; // deafault is false - detects features between multiple surfaces

}



// Settings for the layer addition.
addLayersControls //add the PATCH names from inside the STL file so STLpatchName_insideSTLName
{
relativeSizes false; // was true
layers
{
wall
{nSurfaceLayers 3;} // was 3
//visc_refine_1
// {nSurfaceLayers 3;} // was 3
//visc_refine_2
// {nSurfaceLayers 3;} // was 3
}

expansionRatio 1.3;
finalLayerThickness 0.00016; //was 0.00016
minThickness 0.00008; //was 0.00008
nGrow 0; // was 1


// Advanced settings

featureAngle 80; // was 70 //- When not to extrude surface. 0 is flat, 90 is right angle.
nRelaxIter 3; //- Max# of snapping relaxation iter. Should stop before upon reaching a correct mesh.
nSmoothSurfaceNormals 1; // Number of smoothing iterations of surface normals
nSmoothNormals 3; // Number of smoothing iterations of interior mesh movement direction
nSmoothThickness 10; // Smooth layer thickness over surface patches
maxFaceThicknessRatio 0.5; // Stop layer growth on highly warped cells
maxThicknessToMedialRatio 0.3; // Reduce layer growth where ratio thickness to medial distance is large
minMedianAxisAngle 130; // Angle used to pick up medial axis points
nBufferCellsNoExtrude 0; // Create buffer region for new layer terminations
nLayerIter 50; // Overall max number of layer addition iterations
}



// Generic mesh quality settings. At any undoable phase these determine
// where to undo.
meshQualityControls
{
maxNonOrtho 65;
maxBoundarySkewness 20;
maxInternalSkewness 4;
maxConcave 80;
minFlatness 0.5;
minVol 1e-13;
minTetQuality 1e-9;
minArea -1;
minTwist 0.02;
minDeterminant 0.001;
minFaceWeight 0.02;
minVolRatio 0.01;
minTriangleTwist -1;

// Advanced

nSmoothScale 4;
errorReduction 0.75;
}

// Advanced

debug 0;


// Merge tolerance. Is fraction of overall bounding box of initial mesh.
// Note: the write tolerance needs to be higher than this.
mergeTolerance 1E-6;


// ************************************************** *********************** //