[Vinzmann]

Hello everybody,

I have a small channel in my geometry which is a kind of nozzle. My problem is that my mesh in this channel always looks horrible.

I'd be very thankful if you could take a look at my snappyHexMeshDict and my meshQualityDict.

The small geometry is called duese and the inlet sits at the face of this channel.

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  8                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     8;
    format      ascii;
    class       dictionary;
    object      snappyHexMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

// Which of the steps to run
castellatedMesh true;
snap            true;
addLayers       true;
keepPatches	yes;


geometry
{
   	rohr.stl
    	{
        	type triSurfaceMesh;
        	name rohr;
		inGroups (walls);
    	}

    	inlet.stl
    	{
        	type triSurfaceMesh;
        	name inlet;
    	}
	
    	cOut.stl
    	{
        	type triSurfaceMesh;
        	name cOutlet;
		inGroups (outlets);
    	}
	
	wOut.stl
    	{
        	type triSurfaceMesh;
        	name wOutlet;
    		inGroups (outlets);
	}
	
	drossel.stl
	{
        	type triSurfaceMesh;
		name drossel;
		inGroups (walls);
	}
	
	duese.stl
	{
		type triSurfaceMesh;
		name duese;
		inGroups (dueseGroup);
	}
	
	kammer.stl
    	{
        	type triSurfaceMesh;
        	name kammer;
		inGroups (walls);
    	}

	globalRefinement
	{
		type	searchableCylinder;
		point1	(0 0 0.1);
		point2	(0 0 0.2);
		radius	0.02;
	}

		
};




castellatedMeshControls
{


    maxLocalCells 10000000; 

    maxGlobalCells 200000000; 


    minRefinementCells 5; 

  


    nCellsBetweenLevels 5; 




    features
    (
        {
            	file "rohr.eMesh";
            	level 4; 
        }
		
	{
            	file "drossel.eMesh";
            	level 1; 
        }
		
	{
		file "duese.eMesh";
		level 3;
	}
		
        {
        	file "inlet.eMesh";
        	level 3; 
        }
		
	{
        	file "wOut.eMesh";
        	level 1; 
        }
		
        {
        	file "cOut.eMesh";
        	level 1; 
        }
		
	{
        	file "kammer.eMesh";
        	level 1; 
        }

    );





    refinementSurfaces
    {


	"(rohr)"
        {
            level (3 3); 
            patchInfo
            {
                type wall;
		inGroups (walls);
            }
        }
	
	"(kammer)"
        {
            	level (1 3); 
            	patchInfo
            {
                type wall;
		inGroups (walls);
            }
        }
		
	"(drossel)"
        {
            level (1 1); 
			gapLevelIncrement 2;
            patchInfo
            {
                type wall;
		inGroups (walls);
            }
        }
		
	"(duese)"
        {
            level (5 5); 
            patchInfo
            {
                type wall;
                inGroups (dueseGroup);
            }
        }

	"(inlet)"
        {
            level (5 5); 
            patchInfo
            {
                
		type mappedPatch;
        	offset          (0 0.1 0);
        	sampleRegion    region0;
        	sampleMode      nearestCell;
        	samplePatch     none;
            }
        }
		
	"(cOutlet)"
        {
            level (1 1); 
            patchInfo
            {
                type patch;
                inGroups (outlets);
            }
        }
		
	"(wOutlet)"
        {
            level (1 1); 
            patchInfo
            {
                type patch;
             	inGroups (outlets);
            }
        }
    }

    resolveFeatureAngle 30; 



    refinementRegions
    {

		globalRefinement
		{
			mode	inside;
			levels	((1e15 1));
			gapMode	mixed;
			gapLevel (4 0 4); 
		}
		
		rohr
		{
			mode distance;
			levels ((0.001 2));
		}
		
		inlet
		{
			mode distance;
			levels ((0.002 2));
		}
				
		kammer
		{
			mode distance;
			levels ((0.001 2));
		}
		
		drossel
		{
			mode distance;
			levels ((0.0004 4) (0.0008 3));
		}

    }


 
    locationInMesh (0.001 0.001 0.1);


 
    allowFreeStandingZoneFaces true;
	
	
	
}



snapControls
{
    nSmoothPatch 1; 

  
    nSmoothInternal 1; 

    tolerance 0.7; 

    nSolveIter 100; 

    nRelaxIter 8; 



        nFeatureSnapIter 80;

        implicitFeatureSnap false;

        explicitFeatureSnap true;

        multiRegionFeatureSnap false;
}



addLayersControls
{

    relativeSizes true; 
    	layers
    	{

		walls
		{
			nSurfaceLayers	7;
			
		}
		
		duese
		{
			nSurfaceLayers	10;
		}

		inlet
		{
			nSurfaceLayers	6;
			thickness	2;
			expansionRatio	1;
		}


	}

    expansionRatio 1.2;

    	//finalLayerThickness 2;
	thickness 2;

    minThickness 0.0001; 

 
    nGrow 0;


    featureAngle 230; 

    slipFeatureAngle 90; 

    nRelaxIter 1;

    nSmoothSurfaceNormals 2;

    nSmoothNormals 3; 

    nSmoothThickness 10; 

    maxFaceThicknessRatio 0.3;

    maxThicknessToMedialRatio 0.3;

    minMedialAxisAngle 90;

    nBufferCellsNoExtrude 0;

    nLayerIter 50; 

    nRelaxedIter 1;

	additionalReporting true;
}




meshQualityControls
{
    #include "meshQualityDict"
    relaxed
    {
        maxNonOrtho 35;
    }

	maxNonOrtho 35;
    nSmoothScale 8;
    errorReduction 1.5;
}



writeFlags
(
    scalarLevels
    layerSets
    layerFields     
);



mergeTolerance 1e-6;


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

My meshQualityDict looks like this:

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  8                                     |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      meshQualityDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

minFaceWeight 0.02;
maxBoundarySkewness     3;//20
maxInternalSkewness     2;//4
maxConcave              30;//40
minVol                  1e-13;
minTetQuality           1e-3;//1e-15
minArea                 -1;
minTwist                0.02;
minDeterminant          0.01;//0.001
minFaceWeight           0.05;//0.05
minFaceFlatness         -1;
minVolRatio             0.01;//0.01
minTriangleTwist        -1;
nSmoothScale            8;//8
errorReduction          1.5;//.75


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

I've attached a picture of the mesh.

Best regards,
Vinz