CFD Online Discussion Forums - [snappyHexMesh] Advice on how to keep cells inside a closed contour

Hi Foamers,
I'm new to OF and so i'm struggling with a complex structure.
My structure has a curve configuration and on top of that there's a bunch of openings (see picture).
My problem is that after running SHM the contour of the structure+openings isn't deleted and only the cells between the openings and inside the contour are kept.
The .stl was created using Salome and with Helyx i saw that it was ok.
As you can see in the picture, the SHM is cutting the main contour (structure) but keeping the cells of the openings assuming that it isn't a contour.
I wanna create "holes" in the mesh to let the fluid pass through.
I tried to use a different .stl for the openings but the result was the same.
After some research i thought that maybe if i use multiRegionFeatureSnap the problem could be solved. But it persisted.

Can anyone, please, tell me if there's a way of doing this and give me some guidance?

Best regards

Cristina

Openings:
https://www.dropbox.com/s/ulcj371mt7...te181.bmp?dl=0

Problem:
https://www.dropbox.com/s/pq1pl8aoyo...tura2.png?dl=0

SHM:

Code:

/*--------------------------------*- C++ -*----------------------------------*\

| =========                 |                                                 |

| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |

|  \\    /   O peration     | Version:  2.2.0                                 |

|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |

|    \\/     M anipulation  |                                                 |

\*---------------------------------------------------------------------------*/

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;   // decide to add viscous layers ?





geometry // Load in STL files here

{

    ramp.stl {type triSurfaceMesh; name ramp;}



    refinementBox {type searchableBox; min (0.0 0.0 0.32); max (9.86 0.33 0.54);}

};



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 "ramp.eMesh"; level 3;} 



    );



    // Surface based refinement

    // ~~~~~~~~~~~~~~~~~~~~~~~~



    refinementSurfaces // Surface-wise min and max refinement level

    {

    ramp {level (3 3);}



    }  





    resolveFeatureAngle 80;  // Resolve sharp angles // Default 30

    refinementRegions        // In descending levels of fine-ness

    {volume {mode distance; levels ((0.0006 4) (0.002 3) (0.01 2));}} // was ((0.001 4) (0.003 3) (0.01 2))

    locationInMesh (0 0.02 0);  //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

    





implicitFeatureSnap false; // default is false - detects without doing surfaceFeatureExtract

explicitFeatureSnap true; // default is true

multiRegionFeatureSnap true; // 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

    {



    }



    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;