[namsivag]

Hello all,
I am trying to create fluid and solid meshes (including interface) using snappyHexMesh v1912 for a CHT simulation. I want to study the Heat Transfer between fluid and solid pipe.
I have issues at the highlighted locations in the attached images.
Please give your suggestions to improve. I could not find where I am committing a mistake.
Thanks a lot in advance.
Cheers, Sivam

I codes and values I am using.
BlockMeshDict

scale 1; // convertToMeters does nothing in this case, 0.1 would shrink it by 10x 

vertices   // (x y z)
(
(   -0.0150 -0.0130 -0.0130  )   // in metres // vertex : 0
(   0.0550  -0.0130 -0.0130  )   // in metres // vertex : 1
(   0.0550 0.0130  -0.0130  )   // in metres // vertex : 2
(   -0.0150 0.0130  -0.0130  )   // in metres // vertex : 3
(   -0.0150 -0.0130 0.0130   )   // in metres // vertex : 4
(   0.0550  -0.0130 0.0130   )   // in metres // vertex : 5
(   0.0550 0.0130 0.0130   )   // in metres // vertex : 6
(   -0.0150 0.0130 0.0130   )   // in metres // vertex : 7
);

blocks          
( //                         Divisions 
hex (0 1 2 3 4 5 6 7) baseMesh (46 17 17)   simpleGrading (1 1 1)
);

edges           
(
);

patches         // Boundaries or faces
(               
);

mergePatchPairs
(
  );

topoSetDict

actions
(
// outside Cylinder Cell set
    {
        name solidCellSet;
        type cellSet;
        action new;
        source surfaceToCell;
        sourceInfo
        {
            file "constant/triSurface/solid.stl";
            // use closed surface inside/outside
            // test (ignores includeCut, outsidePoints)
            useSurfaceOrientation false;
            outsidePoints   ((0.01 0 0));   // definition of outside
            includeCut      true;           // cells cut by surface
            includeInside   false;          // cells not on outside of surf
            includeOutside  false;          // cells on outside of surf
            nearDistance    -1;             // cells with centre near surf (set to -1 if not used)
            curvature       0.9;            // cells within nearDistance and near surf curvature (set to -100 if not used)
        }
    }
// outside Cylinder Zone set
    {
        name    solidZone;
        type    cellZoneSet;
        action  new;
        source  setToCellZone;
        sourceInfo
        {
            set solidCellSet; 
        }
    }
// inside Cylinder Cell set
    {
        name fluidCellSet;
        type cellSet;
        action new;
        source surfaceToCell;
        sourceInfo
        {
            file "./constant/triSurface/fluid.stl";
            // use closed surface inside/outside
            // test (ignores includeCut, outsidePoints)
            useSurfaceOrientation false;
            outsidePoints   ((0.01 0 0));   // definition of outside
            includeCut      true;           // cells cut by surface
            includeInside   false;          // cells not on outside of surf
            includeOutside  false;          // cells on outside of surf
            nearDistance    -1;             // cells with centre near surf (set to -1 if not used)
            curvature       0.9;            // cells within nearDistance and near surf curvature (set to -100 if not used)
        }
    }
// inside Cylinder Zone set
    {
        name    fluidZone;
        type    cellZoneSet;
        action  new;
        source  setToCellZone;
        sourceInfo
        {
            set fluidCellSet; 
        }
    }
// combine fluidCell + solidCell set
    {
        name    fluidSolidSet;
        type    cellSet;
        action  new;
        source cellToCell;
        sourceInfo
        {
            set solidCellSet;
            set fluidCellSet;
        }
    }
// invert to get the remaining Set
    {
        name    fluidSolidSet;
        type    cellSet;
        action  invert;
    }
// remaining set to remaining zone
    {
        name    baseZone;
        type    cellZoneSet;
        action  new;
        source  setToCellZone;
        sourceInfo
        {
            set fluidSolidSet;
        }
    }
// remove the remaining zone    
    {
        name    baseZone;
        type    cellZoneSet;
        action  remove;
    }
 );

surfaceFeatureExtractDict

inlet.stl
    {
        extractionMethod    extractFromSurface;
        extractFromSurfaceCoeffs
        {includedAngle   150;}
        writeObj                no;
    } 
fluid.stl
    {
        extractionMethod    extractFromSurface;
        extractFromSurfaceCoeffs
        {includedAngle   150;}
        writeObj                no;
    }
fluidOuter.stl
    {
        extractionMethod    extractFromSurface;
        extractFromSurfaceCoeffs
        {includedAngle   150;}
        writeObj                no;
    }    
outlet.stl
    {
        extractionMethod    extractFromSurface;
        extractFromSurfaceCoeffs
        {includedAngle   150;}
        writeObj                no;
    }  
solid.stl
    {
        extractionMethod    extractFromSurface;
        extractFromSurfaceCoeffs
        {includedAngle   150;}
        writeObj                no;
    } 
solidInner.stl
    {
        extractionMethod    extractFromSurface;
        extractFromSurfaceCoeffs
        {includedAngle   150;}
        writeObj                no;
    }  
solidOuter.stl
    {
        extractionMethod    extractFromSurface;
        extractFromSurfaceCoeffs
        {includedAngle   150;}
        writeObj                no;
    }      
inletPipe.stl
    {
        extractionMethod    extractFromSurface;
        extractFromSurfaceCoeffs
        {includedAngle   150;}
        writeObj                no;
    }      
     writeFeatureEdgeMesh    yes;

snappyHexMeshDict

castellatedMesh true;    // make basic mesh ?
snap            true;    // decide to snap back to surface ?
addLayers       true;    // decide to add viscous layers ?
// singleRegionName false;  // Optional

geometry
{
    fluid.stl     {type triSurfaceMesh; name fluid ; }
    // fluid.stl {type triSurfaceMesh;
    // regions      {fluid {name fluid;}}}

    solid.stl    {type triSurfaceMesh; name solid; }
    // solid.stl {type triSurfaceMesh;
    // regions      {solid {name solid;}}}

    // inlet.stl {type triSurfaceMesh;
    // regions      {inlet {name inlet;}}}

    // outlet.stl {type triSurfaceMesh;
    // regions      {outlet {name outlet;}}}

    // inletPipe.stl {type triSurfaceMesh;
    // regions      {inletPipe {name inletPipe;}}}    

    
    inlet.stl      {type triSurfaceMesh; name inlet     ; }
    outlet.stl     {type triSurfaceMesh; name outlet    ; }
    inletPipe.stl  {type triSurfaceMesh; name inletPipe ; }
    fluidOuter.stl {type triSurfaceMesh; name fluidOuter ; }
    solidInner.stl {type triSurfaceMesh; name solidInner ; }
};

castellatedMeshControls
{
    maxLocalCells 10000000;
    maxGlobalCells 20000000;
    minRefinementCells 10;//10;
    maxLoadUnbalance 0.10;//0.10;
    nCellsBetweenLevels 4;//4;

    features // taken from STL from each .eMesh file created by "SurfaceFeatureExtract" command
    (
        {file "fluid.eMesh";      level 2;}
        {file "solid.eMesh";      level 2;}
        {file "outlet.eMesh";     level 2;}
        {file "inlet.eMesh";      level 2;}
        {file "inletPipe.eMesh";  level 2;}
        {file "fluidOuter.eMesh";  level 2;}
        {file "solidInner.eMesh";  level 2;}
    );

    refinementSurfaces // Surface-wise min and max refinement level
    {
        fluid{
            level (2 2); // (min max )
            faceZone fluid;
            cellZone fluid;
            cellZoneInside inside;            
            }

        solid{
            level (2 2);
            faceZone solid;
            cellZone solid;
            cellZoneInside inside;                        
            }

        inlet     { level ( 1 2 ) ; patchInfo { type patch; } } 
        outlet    { level ( 1 2 ) ; patchInfo { type patch; } } 
        inletPipe { level ( 1 2 ) ; patchInfo { type wall;  } }
        // fluidOuter { level ( 1 2 ) ; patchInfo { type wall;  } }
        // solidInner { level ( 1 2 ) ; patchInfo { type wall;  } }
    }

    resolveFeatureAngle 10;//20;//30;//80
    refinementRegions        // In descending levels of fine-ness
    {
        fluid        {mode inside; levels ((2 1));}
        solid        {mode inside; levels ((2 1));}
    }
    locationInMesh (0.01 0.0 0.0); // in metres

    // locationsInMesh // in metres
    // (
    //     (( 0.0  0.0     0.0) inside)
    //     (( 3e-3 6.5e-3  0.0) outside)
    // );

    allowFreeStandingZoneFaces true;
}

snapControls
{
    nFaceSplitInterval  5;
    nSmoothPatch 5;
    tolerance    1.0;//4.0;
    nSolveIter   60;//300;//60;
    nRelaxIter   5;//10;//5;
    nFeatureSnapIter 10;//15; // default is 10
    implicitFeatureSnap false; // default is false - detects without doing surfaceFeatureExtract
    explicitFeatureSnap true; // default is true
    multiRegionFeatureSnap true; // deafault is false - detects features between multiple surfaces
}

addLayersControls
{
    relativeSizes true;
    layers
    {
       fluid_slave
        {
         nSurfaceLayers 3; // was 5
        }
    }
    expansionRatio 1.5;
    finalLayerThickness 5e-3;
    minThickness 5e-4;
    nGrow 0;//was 1;
    featureAngle 110;//85;//30;
    nRelaxIter 5;//3;
    nSmoothSurfaceNormals 4;//1;
    nSmoothNormals 3;
    nSmoothThickness 10;
    maxFaceThicknessRatio 0.5;
    maxThicknessToMedialRatio 0.2;//0.3;
    minMedianAxisAngle 90;//130;
    nBufferCellsNoExtrude 0;
    nLayerIter 50;
    detectExtrusionIsland true;    
}
meshQualityControls
{
    maxNonOrtho 65;
    maxBoundarySkewness 20;
    maxInternalSkewness 4;
    maxConcave 80;
    minFlatness 0.5;
    minVol 1e-13;
    minArea -1;
    minTwist 0.02;
    minDeterminant 0.001;
    minFaceWeight 0.02;
    minVolRatio 0.01;
    minTetQuality 1e-30;
    minTriangleTwist -1;
    nSmoothScale 4;
    errorReduction 0.75;
}
debug 0;
writeFlags
(
    scalarLevels
    layerSets
    layerFields     // write volScalarField for layer coverage
);
mergeTolerance 1E-6;

[Rango]

Hi,


Just a few observations that may help:

1. Turn off the "addLayers" option and see if you can get a sharp edge at inlet.
2. Edit "refinementSurfaces" section to

   refinementSurfaces // Surface-wise min and max refinement level
       {
           fluid{
               level (0 0); // (min max )
               faceZone fluid;
               cellZone fluid;
               cellZoneInside inside;            
               }
   
           solid{
               level (0 0);
               faceZone solid;
               cellZone solid;
               cellZoneInside inside;                        
               }
   
           inlet     { level (2 2 ) ; patchInfo { type patch; } } 
           outlet    { level ( 2 2 ) ; patchInfo { type patch; } } 
         
       }

   and "refinementRegions" section to

   refinementRegions        // In descending levels of fine-ness
       {
           fluid        {mode inside; levels ((2 2));}
           solid        {mode inside; levels ((2 2));}
       }

3. Do you need to include "featureEdge (eMesh files)" for every single "stl" file that you have?
4. Increase "resolveFeatureAngle" to 60.
5. Turn off "multiRegionFeatureSnap".

Cheers

[namsivag]

Dear Rango,
Thanks for the values. Sharp edges are generated at inlet of fluid domain.

Your query :
Do you need to include "featureEdge (eMesh files)" for every single "stl" file that you have?
I thought that "featureEdge (eMesh files)" might improve the meshes at the edges.

Some more help needed.
A. I have some issues at the edges on fluid and solid surfaces at interface starting location. I have highlighted on the attached images.
B. I would like to get rid of the baseMesh interfaces with the solid and fluid surfaces. I have highlighted on the attached images.

Thanks again.
Cheers, Sivam

I am sharing the codes and images.

castellatedMesh true;    // make basic mesh ?
snap            true;    // decide to snap back to surface ?
addLayers       false;    // decide to add viscous layers ?

geometry
{
    fluid.stl    {type triSurfaceMesh; name fluid; }
    solid.stl    {type triSurfaceMesh; name solid; }

    inlet.stl      {type triSurfaceMesh; name inlet     ; }
    outlet.stl     {type triSurfaceMesh; name outlet    ; }
    inletPipe.stl  {type triSurfaceMesh; name inletPipe ; }
};

castellatedMeshControls
{
    maxLocalCells  10000000;
    maxGlobalCells 20000000;
    minRefinementCells 10;
    maxLoadUnbalance 0.10;
    nCellsBetweenLevels 4;

    features // taken from STL from each .eMesh file created by "SurfaceFeatureExtract" command
    (
        {file "fluid.eMesh";      level 2;}
        {file "solid.eMesh";      level 2;}
        {file "outlet.eMesh";     level 2;}
        {file "inlet.eMesh";      level 2;}
        {file "inletPipe.eMesh";  level 2;}
    );

    refinementSurfaces // Surface-wise min and max refinement level
    {
        fluid{
            level (0 0); // (min max )
            faceZone fluid;
            cellZone fluid;
            cellZoneInside inside;            
            }

        solid{
             level (0 0);
            faceZone solid;
            cellZone solid;
            cellZoneInside inside;                        
            }

        inlet     { level ( 2 2 ) ; patchInfo { type patch; } } 
        outlet    { level ( 2 2 ) ; patchInfo { type patch; } } 
        // inletPipe { level ( 1 2 ) ; patchInfo { type wall;  } }
    }

     resolveFeatureAngle 60;
    refinementRegions      // In descending levels of fine-ness
    {
        fluid        {mode inside; levels ((2 2));}
        solid        {mode inside; levels ((2 2));}
    }
    locationInMesh (0.01 0.0 0.0); // in metres
    allowFreeStandingZoneFaces true;
}

snapControls
{
    nFaceSplitInterval  5;
    nSmoothPatch        5;
    tolerance         1.0; // 4.0;
    nSolveIter         60; // 300;
    nRelaxIter          5; // 10;
    nFeatureSnapIter   10; // default is 10
    
    implicitFeatureSnap    false; // default is false - detects without doing surfaceFeatureExtract
    explicitFeatureSnap    true;  // default is true
     multiRegionFeatureSnap false;


 }

addLayersControls
{
    relativeSizes true;
    layers
    {
       fluid_slave
        {
         nSurfaceLayers 3;
        }
    }
    expansionRatio            1.5;
    finalLayerThickness      5e-3;
    minThickness             5e-4;
    nGrow                       0;//was 1;
    featureAngle              110;//85;//30;
    nRelaxIter                  5;//3;
    nSmoothSurfaceNormals       4;//1;
    nSmoothNormals              3;
    nSmoothThickness           10;
    maxFaceThicknessRatio     0.5;
    maxThicknessToMedialRatio 0.2;//0.3;
    minMedianAxisAngle         90;//130;
    nBufferCellsNoExtrude       0;
    nLayerIter                 50;
    detectExtrusionIsland    true;    
}
meshQualityControls
{
    maxNonOrtho         65;
    maxBoundarySkewness 20;
    maxInternalSkewness  4;
    maxConcave          80;
    
    minFlatness        0.5;
    minVol           1e-13;
    minArea             -1;
    minTwist          0.02;
    
    minDeterminant   0.001;
    minFaceWeight     0.02;
    minVolRatio       0.01;
    minTetQuality    1e-30;
    
    minTriangleTwist    -1;
    nSmoothScale         4;
    errorReduction    0.75;
}
debug 0;
writeFlags
(
    scalarLevels
    layerSets
    layerFields     // write volScalarField for layer coverage
);
mergeTolerance 1E-6;

[namsivag]

Hallo,
I have two surfaces solidHeadBottom (surf-1) and interface2fluid (surf-2).
Mesh at the circular edge is not proper. Please have a look at highlighted areas on the attached images. Could you please help me to cross this issue !!
Thanks a lot in advance.
regards, Sivam

FoamFile{
     version     2.0;
    format      ascii;
    class       dictionary;
    object      snappyHexMeshDict;}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
castellatedMesh true;
snap true;
addLayers false;

geometry
{
    solidHead.stl       {type triSurfaceMesh; name head;  }
    outerSolidHead.stl  {type triSurfaceMesh; name outerSolidHead;}
    solidHeadBottom.stl {type triSurfaceMesh; name solidHeadBottom;}
    interface2fluid.stl {type triSurfaceMesh; name interface2fluid;}
};

castellatedMeshControls
{
    maxLocalCells       10000000;
    maxGlobalCells      20000000;
    minRefinementCells  100;
    maxLoadUnbalance    0.10;
    nCellsBetweenLevels 4; //4;

    features
    (
        // {file "solidHead.eMesh";       level 2;} //2
        {file "outerSolidHead.eMesh";  level 2;} //2
        {file "solidHeadBottom.eMesh"; level 2;} //2
        {file "interface2fluid.eMesh"; level 2;} //2
    );

    refinementSurfaces // Surface-wise min and max refinement level
    {
        head{
            level          (0 1); //0 0
            faceZone       head;
            cellZone       head;
            cellZoneInside inside;
            boundary       internal;
            }
        //            
        outerSolidHead  {level (1 2); patchInfo { type wall;}} // 1 1
        solidHeadBottom {level (1 2); patchInfo { type wall;}} // 1 2
        interface2fluid {level (1 2); patchInfo { type wall;}} // 1 2
    }
    resolveFeatureAngle 60;
    refinementRegions      // In descending levels of fine-ness
    {
        head           {mode inside; levels ((1 1));}
    }
    locationInMesh (0.0  0.0  0.071); // Inside point
    allowFreeStandingZoneFaces false;
}

snapControls
{
    nFaceSplitInterval  5;
    nSmoothPatch        5;
    nSmoothInternal     $nSmoothPatch;
    tolerance         4.0;
    nSolveIter         300;//60
    nRelaxIter         10;
    nFeatureSnapIter   10; // default is 10
    
    implicitFeatureSnap    true; // default is false - detects without doing surfaceFeatureExtract
    explicitFeatureSnap    false;  // default is true
    multiRegionFeatureSnap false; // default is false - detects features between multiple surfaces
}

addLayersControls
{
    relativeSizes false;
    layers
        {fluid_slave {nSurfaceLayers 3;}}
    expansionRatio            1.2;
    finalLayerThickness      5e-3;
    minThickness             3e-3;
    nGrow                       1;//was 0;
    featureAngle              110;//85;//30;
    nRelaxIter                  5;//3;
    nSmoothSurfaceNormals       4;//1;
    nSmoothNormals              3;
    nSmoothThickness           10;
    maxFaceThicknessRatio     0.5;
    maxThicknessToMedialRatio 0.2;//0.3;
    minMedianAxisAngle         90;//130;
    nBufferCellsNoExtrude       0;
    nLayerIter                 50;
    layerTerminationAngle    -180;
    detectExtrusionIsland    true;    
}
meshQualityControls
{
    maxNonOrtho         180;//65;
    maxBoundarySkewness  20;
    maxInternalSkewness   4;
    maxConcave           80;
    
    minFlatness         0.5;
    minVol            1e-13;
    minArea              -1;
    minTwist           0.02;
    
    minDeterminant    0.001;
    minFaceWeight      0.02;
    minVolRatio        0.01;
    minTetQuality     1e-30;
    
    minTriangleTwist     -1;
    nSmoothScale          4;
    errorReduction     0.75;
}
debug 0;
writeFlags
(
    scalarLevels
    layerSets
    layerFields     // write volScalarField for layer coverage
);
mergeTolerance 1E-6;