CFD Online Discussion Forums - [snappyHexMesh] sHM layer reduction towards outlet

Code:
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FoamFile

{

    version     2.0;

    format      ascii;

    class       dictionary;

    object      snappyHexMeshDict;  

}

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



// Which of the steps to run

castellatedMesh     true;

meshQuality         true;

snap                true;

addLayers           true;





geometry

{



var1e_swx_from_icem_flaechen_benannt_cutted.stl

        {

            type triSurfaceMesh;

        name var1e_swx_from_icem_flaechen_benannt_cutted;

        regions

        {

            OUTLETS        {    name outlets;}

            ROHRE        {    name rohre;}

            INLET        {    name inlet;}

            QUERKANAL1    {    name querkanal1;}

            QUERKANAL2    {    name querkanal2;}

            QUERKANAL3    {    name querkanal3;}

            KRUEMMER1    {    name kruemmer1;}

            /*KRUEMMER2    {    name kruemmer2;}

            KRUEMMER3    {    name kruemmer3;}

            KRUEMMER4    {    name kruemmer4;}*/

            HEADER1        {    name header1;}

            HEADER2        {    name header2;}

            HEADER3        {    name header3;}

            HEADER4        {    name header4;}

            HEADER5        {    name header5;}

            HEADER6        {    name header6;}

            HEADER7        {    name header7;}

            HEADER8        {    name header8;}

            /*HEADER9        {    name header9;}

            HEADER10    {    name header10;}

            HEADER11    {    name header11;}

            HEADER12    {    name header12;}*/

            SYMM        {    name symm;}

        }

    }





feinebox

    {

    type searchableBox;

    min (3     8    0);

    max (26    8.3    6);

    }

    

};





castellatedMeshControls

{

    

     maxGlobalCells     40000000;

     maxLocalCells         1000000;

     minRefinementCells 0;

     nCellsBetweenLevels 3;



    features

    (

        {    file     "var1e_swx_from_icem_flaechen_benannt_cutted.eMesh";            level 0;    }

        

        

        



);        



    refinementSurfaces

    {

    var1e_swx_from_icem_flaechen_benannt_cutted

    {

        level (2 3);

            regions

            {

                      rohre        {    level (2 3);        }

                      outlets        {    level (2 3);        }

                      inlet        {    level (2 3);        }

                      querkanal1    {    level (2 3);        }

                      querkanal2    {    level (2 3);        }

                      querkanal3    {    level (2 3);        }

                      kruemmer1    {    level (2 3);        }

                      /*kruemmer2    {    level (2 3);        }

                      kruemmer3    {    level (2 3);        }

                      kruemmer4    {    level (2 3);        }*/

                      header1        {    level (2 3);        }

                      header2        {    level (2 3);        }

                      header3        {    level (2 3);        }

                      header4        {    level (2 3);        }

                      header5        {    level (2 3);        }

                      header6        {    level (2 3);        }

                      header7        {    level (2 3);        }

                      header8        {    level (2 3);        }

                      symm        {    level (2 3);        }

                      inlet        {    level (2 3);        }

                      outlets        {    level (2 3);        }

                      //header12    {    level (2 3);        }



        

            }

        }

     }

    refinementRegions 

        {    

        feinebox        

               {        

                    mode inside;

                    levels ((1E15 0));

            }

        

         }  

    

    resolveFeatureAngle 30;



    allowFreeStandingZoneFaces true;   



    locationInMesh (5.0005000511194281582016 9.007272265124 1.00005000014285523886);



    maxLoadUnbalance 0.10;

    

}





addLayersControls

{

       // Are the thickness parameters below relative to the undistorted

        // size of the refined cell outside layer (true) or absolute sizes (false).

    relativeSizes true;

        // 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.

    //  See relativeSizes parameter.

    thickness 0.2; 

    firstLayerThickness 0.2; 

    //- 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 0.000001;





    /* möglich sind:

    first layer thickness ('firstLayerThickness') and overall thickness ('thickness') or

    first layer thickness ('firstLayerThickness') and expansion ratio ('expansionRatio') or

    final layer thickness ('finalLayerThickness') and expansion ratio ('expansionRatio') or

    final layer thickness ('finalLayerThickness') and overall thickness ('thickness') or

    overall thickness ('thickness') and expansion ratio ('expansionRatio'

    */



    layers

            {

            rohre        { nSurfaceLayers 1;   }        

            querkanal1    { nSurfaceLayers 1;   }    

            querkanal2    { nSurfaceLayers 1;   }    

            querkanal3    { nSurfaceLayers 1;   }    

            kruemmer1    { nSurfaceLayers 1;   }    

            /*kruemmer2    { nSurfaceLayers 1;   }    

            kruemmer3    { nSurfaceLayers 1;   }    

            kruemmer4    { nSurfaceLayers 1;   }*/

            header1        { nSurfaceLayers 1;   }

            header2        { nSurfaceLayers 1;   }    

            header3        { nSurfaceLayers 1;   }    

            header4        { nSurfaceLayers 1;   }    

            header5        { nSurfaceLayers 1;   }    

            header6        { nSurfaceLayers 1;   }    

            header7        { nSurfaceLayers 1;   }    

            header8        { nSurfaceLayers 1;   }    

            //symm        { nSurfaceLayers 1;   }    

            //inlet        { nSurfaceLayers 1;   }    

            outlets        { nSurfaceLayers 0;   }    

            //header12    { nSurfaceLayers 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.

    //      This specifies the number of layers of connected faces that are not grown. This helps in convergence of the layer addition               process close to features.

    nGrow 0;



    // Advanced settings



        //- When not to extrude surface. 0 is flat surface, 90 is when two faces

        //  make straight angle.

    featureAngle 210; //180; //130    

    SlipFeatureAngle 75;

    //- Maximum number of snapping relaxation iterations. Should stop

       //  before upon reaching a correct mesh.

        nRelaxIter 40;

    // Number of smoothing iterations of surface normals

    nSmoothSurfaceNormals 6;//3

    // Number of smoothing iterations of interior mesh movement direction

    nSmoothNormals 6;//3

    // Smooth layer thickness over surface patches

    nSmoothThickness 30;//10

    // Stop layer growth on highly warped cells

    // This specifies the maximum allowable value of aspect ratio. Sometimes (especially in corners) the layers must be generated over            highly warped cells. The layer generation will stop for cells where aspect ratio is higher than this value.

    maxFaceThicknessRatio 50;//0.5;

    // Reduce layer growth where ratio thickness to medial

        // distance is large

    maxThicknessToMedialRatio 0.8;//0.3

    // Angle used to pick up medial axis points

    minMedianAxisAngle 90;    

    // Create buffer region for new layer terminations

    nBufferCellsNoExtrude 2; //0

    // Overall max number of layer addition iterations

    nLayerIter 50;

    // No of steps walking away from the surface (to stop dislocations walking through the mesh)

    nMedialAxisIter 1000; // default: 2^31 (unlimited)

}

 

snapControls

{



    nSmoothPatch 5;//3            von 3 im vgl zu #1





    tolerance 1.5; //vorher 1.5



    nSolveIter 300;



    explicitFeatureSnap        true;

    implicitFeatureSnap     false;

    multiRegionFeatureSnap    true;

    nRelaxIter 10;



    nFeatureSnapIter 10;

}



meshQualityControls

{

 

    maxNonOrtho 65;//180; //50; // 65



    maxBoundarySkewness 5;//-1;//20;    von 20 im vgl zu #1



    maxInternalSkewness 4;//-1;//4;     von 0.5 im vgl zu #1



    maxConcave 80;//180;//80;



    minVol 1e-13;//-1e-33;//1e-13;



    minTetQuality 1e-30;//-1e-30;//1e-30;



    minArea -1;



    minTwist 0.02;//-1e-30;  //0.02;



    minDeterminant 0.001;//-1; //0.001; //0.001



    minFaceWeight 0.02;//-1;  //0.02;



    minVolRatio 0.01;//-1;    //0.01;



    minTriangleTwist 0.01;//-1;



    nSmoothScale 4;



    errorReduction 0.75; //0.75; 

}







debug 0;





mergeTolerance 1e-2;





// ************************************************************************* //
Thank you for your answer, this is my sHM dict.
Reuslting from this sHM dict:
Picture #1 shows the transition of the BL from "rohre" to "symm" and pic #2 shows transition from "rohre" to "outlets". In both cases the BL should have been projected onto the face which should have no BL (i.e. symm and outlets respectively). In my sHM dict I tried to either comment out BL for symm or say "zero layers" for "outlets", both don't work.

When you talk about the feature angle.. I also attached 2 pictures that show a parametric study of this angle starting at 90° at the left going to 180° to the right (for the first picture) and a detailed study from 150° t165° to 180°. You can see that none of the cases is satisfying, since the BL either won't go around the corner or is not projected on the left wall where I don't want to have a BL.