[jrrygg]

Hi!

I am working on simulating the flow in a Pelton bucket numerically, but I am having some trouble with the AMI-interface. I think this is related to the meshing in the AMI-patches, as they seem to not be perfectly circular as I want them to be.

I wonder if anyone has some tricks that may help me improve the representation of the flow over the interface? The AMI-patches should be circular, but how can I refine them?

My case is originally based on the propeller-tutorial, but I use the interDyMFoam-solver.

The water jet is cut in the AMI-interface:


AMI1:


AMI2:


My snappyHexMeshDict:

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.1.0                                 |
|   \\  /    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;
snap            true;
addLayers       true; //Originally false


// Geometry. Definition of all surfaces. All surfaces are of class
// searchableSurface.
// Surfaces are used
// - to specify refinement for any mesh cell intersecting it
// - to specify refinement for any mesh cell inside/outside/near
// - to 'snap' the mesh boundary to the surface
geometry
{
    jetinlet.obj
    {
        type        triSurfaceMesh;
        name        jetinlet;
      regions
      {
          jetinlet
         {
                name       jetinlet;
           }
       }

    }

    jetwalls.obj
    {
        type        triSurfaceMesh;
        name        jetwalls;
         regions
         {
             jetwalls
             {
                  name       jetwalls;
             }
         }
    }

    BBC.obj
    {
        type        triSurfaceMesh;
        name        BBC;
         regions
         {
             BBC
             {
                  name       BBC;
            }
         }
    }

    MBC.obj
    {
        type        triSurfaceMesh;
        name        MBC;
         regions
         {
             MBC
             {
                  name       MBC;
            }
         }
    }

    TBC.obj
    {
        type        triSurfaceMesh;
        name        TBC;
         regions
         {
             TBC
             {
                  name       TBC;
            }
         }
    }


    statopening.obj
    {
        type        triSurfaceMesh;
        name        statopening;
         regions
         {
             statopening
             {
                  name       statopening;
             }
         }

    }
    rotif.obj
    {
        type        triSurfaceMesh;
        name        rotif;
         regions
         {
             rotif
             {
                  name       rotif;
             }
         }
    }

    rotopen.obj
    {
        type        triSurfaceMesh;
        name        rotopen;
         regions
         {
             rotopen
             {
                  name       rotopen;
             }
         }
    }
    rotsym.obj
    {
        type        triSurfaceMesh;
        name        rotsym;
         regions
         {
             rotsym
             {
                  name       rotsym;
             }
         }
    }
    statinlet.obj
    {
        type        triSurfaceMesh;
        name        statinlet;
         regions
         {
             statinlet
             {
                  name       statinlet;
             }
         }
    } 

    statsym.obj
    {
        type        triSurfaceMesh;
        name        statsym;
         regions
         {
             statsym
             {
                  name       statsym;
             }
         }
    }

};



// Settings for the castellatedMesh generation.
castellatedMeshControls
{

    // Refinement parameters
    // ~~~~~~~~~~~~~~~~~~~~~

    // If local number of cells is >= maxLocalCells on any processor
    // switches from from refinement followed by balancing
    // (current method) to (weighted) balancing before refinement.
    maxLocalCells 100000;

    // Overall cell limit (approximately). Refinement will stop immediately
    // upon reaching this number so a refinement level might not complete.
    // Note that this is the number of cells before removing the part which
    // is not 'visible' from the keepPoint. The final number of cells might
    // actually be a lot less.
    maxGlobalCells 1000000;

    // The surface refinement loop might spend lots of iterations refining just a
    // few cells. This setting will cause refinement to stop if <= minimumRefine
    // are selected for refinement. Note: it will at least do one iteration
    // (unless the number of cells to refine is 0)
    minRefinementCells 0;

    // Allow a certain level of imbalance during refining
    // (since balancing is quite expensive)
    // Expressed as fraction of perfect balance (= overall number of cells /
    // nProcs). 0=balance always.
    maxLoadUnbalance 0.10;


    // Number of buffer layers between different levels.
    // 1 means normal 2:1 refinement restriction, larger means slower
    // refinement.
    nCellsBetweenLevels 2;



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

    // Specifies a level for any cell intersected by its edges.
    // This is a featureEdgeMesh, read from constant/triSurface for now.
    features
    (
       {
            file        "jetinlet.eMesh";
            level       3;
        }

       {
            file        "jetwalls.eMesh";
            level       3;
        }


       {
            file        "statopening.eMesh";
            level       1;
        }
       {
            file        "rotif.eMesh";
            level       3;
        }
       {
            file        "BBC.eMesh";
            level       3;
        }
       {
            file        "MBC.eMesh";
            level       3;
        } 
       {
            file        "TBC.eMesh";
            level       3;
        } 
//4 nye
       {
            file        "rotopen.eMesh";
            level       1;
        }
{
            file        "rotsym.eMesh";
            level       1;
        }
{
            file        "statinlet.eMesh";
            level       1;
        }
{
            file        "statsym.eMesh";
            level       1;
        }

    );



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

    // Specifies two levels for every surface. The first is the minimum level,
    // every cell intersecting a surface gets refined up to the minimum level.
    // The second level is the maximum level. Cells that 'see' multiple
    // intersections where the intersections make an
    // angle > resolveFeatureAngle get refined up to the maximum level.

    refinementSurfaces
    {
        BBC
        {
            level       (2 3); //Originally (2 3) for all buckets
        }
        MBC
        {
            level       (2 3);
        }

        TBC
        {
            level       (2 3);
        }
        rotif
        {
            level       (2 2);
            cellZone    rotif;
            faceZone    rotif;
            cellZoneInside inside; 
        } 
        statopening
        {
            level       (1 1);
        }
        jetinlet
        {
            level       (2 3);
        }
        jetwalls
        {
            level       (2 3);
        }



//4 nye
        rotopen
        {
            level       (1 1);
        }
        rotsym
        {
            level       (2 2);
        }
        statinlet
        {
            level       (1 1);
        }
        statsym
        {
            level       (2 3);
        }
    }

    // Resolve sharp angles
    resolveFeatureAngle 30;


    // Region-wise refinement
    // ~~~~~~~~~~~~~~~~~~~~~~

    // Specifies refinement level for cells in relation to a surface. One of
    // three modes
    // - distance. 'levels' specifies per distance to the surface the
    //   wanted refinement level. The distances need to be specified in
    //   descending order.
    // - inside. 'levels' is only one entry and only the level is used. All
    //   cells inside the surface get refined up to the level. The surface
    //   needs to be closed for this to be possible.
    // - outside. Same but cells outside.

    refinementRegions
    {
   /*     rotif
        {
            mode        inside;
            levels      ((1E15 3));
        }


        statinlet
        {
            mode        inside;
            levels      ((1E15 0));
        }
*/
	  MBC
         {
             mode        distance;
             levels      ((0.05 5));
         } 
	  TBC
         {
             mode        distance;
             levels      ((0.05 5));
         } 
	  BBC
         {
             mode        distance;
             levels      ((0.05 5));
         } 
	  jetwalls
         {
             mode        distance;
             levels      ((0.01 5));
         } 
	  jetinlet
         {
             mode        distance;
             levels      ((0.01 5));
         } 

    }


    // Mesh selection
    // ~~~~~~~~~~~~~~

    // After refinement patches get added for all refinementSurfaces and
    // all cells intersecting the surfaces get put into these patches. The
    // section reachable from the locationInMesh is kept.
    // NOTE: This point should never be on a face, always inside a cell, even
    // after refinement.
   // locationInMesh (21 601.1 211.1);
   locationInMesh (-0.20545645 0.111378 0.202156456); //Originalt (0.37046464 0.111378 0.37046464)

    // Whether any faceZones (as specified in the refinementSurfaces)
    // are only on the boundary of corresponding cellZones or also allow
    // free-standing zone faces. Not used if there are no faceZones.
    allowFreeStandingZoneFaces true;
}



// Settings for the snapping.
snapControls
{
    //- Number of patch smoothing iterations before finding correspondence
    //  to surface
    nSmoothPatch 5; //Originally 3

    //- Relative distance for points to be attracted by surface feature point
    //  or edge. True distance is this factor times local
    //  maximum edge length.
    tolerance 4.0; // 1.0;

    //- Number of mesh displacement relaxation iterations.
    nSolveIter 20;

    //- Maximum number of snapping relaxation iterations. Should stop
    //  before upon reaching a correct mesh.
    nRelaxIter 6; //Originally 5

    //- Highly experimental and wip: number of feature edge snapping
    //  iterations. Leave out altogether to disable.
    //  Do not use here since mesh resolution too low and baffles present
    nFeatureSnapIter 20;
}



// Settings for the layer addition.
addLayersControls
{
    // Are the thickness parameters below relative to the undistorted
    // size of the refined cell outside layer (true) or absolute sizes (false).
    relativeSizes true;

    // Per final patch (so not geometry!) the layer information
    layers
    {
    }

    // Expansion factor for layer mesh
    expansionRatio 1.0;

    //- Wanted thickness of final added cell layer. If multiple layers
    //  is the
    //  thickness of the layer furthest away from the wall.
    //  Relative to undistorted size of cell outside layer.
    //  is the thickness of the layer furthest away from the wall.
    //  See relativeSizes parameter.
    finalLayerThickness 0.3;

    //- 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 0.1;

    //- 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.
    // Note: changed(corrected) w.r.t 17x! (didn't do anything in 17x)
    nGrow 0;

    // Advanced settings

    //- When not to extrude surface. 0 is flat surface, 90 is when two faces
    //  make straight angle.
    featureAngle 30;

    //- Maximum number of snapping relaxation iterations. Should stop
    //  before upon reaching a correct mesh.
    nRelaxIter 3;

    // Number of smoothing iterations of surface normals
    nSmoothSurfaceNormals 1;

    // Number of smoothing iterations of interior mesh movement direction
    nSmoothNormals 3;

    // Smooth layer thickness over surface patches
    nSmoothThickness 10;

    // Stop layer growth on highly warped cells
    maxFaceThicknessRatio 0.5;

    // Reduce layer growth where ratio thickness to medial
    // distance is large
    maxThicknessToMedialRatio 0.3;

    // Angle used to pick up medial axis points
    // Note: changed(corrected) w.r.t 17x! 90 degrees corresponds to 130 in 17x.
    minMedianAxisAngle 90;


    // Create buffer region for new layer terminations
    nBufferCellsNoExtrude 0;


    // Overall max number of layer addition iterations. The mesher will exit
    // if it reaches this number of iterations; possibly with an illegal
    // mesh.
    nLayerIter 50;
}



// Generic mesh quality settings. At any undoable phase these determine
// where to undo.
meshQualityControls
{
    //- Maximum non-orthogonality allowed. Set to 180 to disable.
    maxNonOrtho 45; //Originally 65

    //- Max skewness allowed. Set to <0 to disable.
    maxBoundarySkewness 20;
    maxInternalSkewness 4;

    //- Max concaveness allowed. Is angle (in degrees) below which concavity
    //  is allowed. 0 is straight face, <0 would be convex face.
    //  Set to 180 to disable.
    maxConcave 80;

    //- Minimum pyramid volume. Is absolute volume of cell pyramid.
    //  Set to a sensible fraction of the smallest cell volume expected.
    //  Set to very negative number (e.g. -1E30) to disable.
    minVol 1e-13;

    //- Minimum quality of the tet formed by the face-centre
    //  and variable base point minimum decomposition triangles and
    //  the cell centre. This has to be a positive number for tracking
    //  to work. Set to very negative number (e.g. -1E30) to
    //  disable.
    //     <0 = inside out tet,
    //      0 = flat tet
    //      1 = regular tet
    minTetQuality -1; // 1e-30;

    //- Minimum face area. Set to <0 to disable.
    minArea -1;

    //- Minimum face twist. Set to <-1 to disable. dot product of face normal
    //- and face centre triangles normal
    minTwist 0.01;

    //- minimum normalised cell determinant
    //- 1 = hex, <= 0 = folded or flattened illegal cell
    minDeterminant 0.001;

    //- minFaceWeight (0 -> 0.5)
    minFaceWeight 0.05;

    //- minVolRatio (0 -> 1)
    minVolRatio 0.01;

    //must be >0 for Fluent compatibility
    minTriangleTwist -1;


    // Advanced

    //- Number of error distribution iterations
    nSmoothScale 6; //Originally 4
    //- amount to scale back displacement at error points
    errorReduction 0.75; 

    // Optional : some meshing phases allow usage of relaxed rules.
    // See e.g. addLayersControls::nRelaxedIter.
    relaxed
    {
        //- Maximum non-orthogonality allowed. Set to 180 to disable.
        maxNonOrtho 45; //Originally 75
    }
}


// Advanced

// Flags for optional output
// 0 : only write final meshes
// 1 : write intermediate meshes
// 2 : write volScalarField with cellLevel for postprocessing
// 4 : write current intersections as .obj files
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;


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

My createAMIFaces.topoSetDict:

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

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

actions
(
    {
        name    rotif;
        type    cellSet;
        action  new;
        source  cylinderToCell;
        sourceInfo
        {
            p1      (0 0 0);

            p2      (0 0.13908 0);
            radius  0.3477;
        }
    }
    {
        name    outerCells;
        type    cellSet;
        action  new;
        source  cellToCell;
        sourceInfo
        {
            set rotif;
        }
    }
    {
        name    outerCells;
        type    cellSet;
        action  invert;
    }

    {
        name    rotif;
        type    cellZoneSet;
        action  new;
        source  setToCellZone;
        sourceInfo
        {
            set     rotif;
        }
    }



    {
        name    rotifFace;
        type    faceSet;
        action  new;
        source  cellToFace;
        sourceInfo
        {
            set     rotif;
            option  all;
        }
    }
    {
        name    rotifFace;
        type    faceSet;
        action  subset;
        source  cellToFace;
        sourceInfo
        {
            set     outerCells;
            option  all;
        }
    }
    {
        name    rotif;
        type    faceZoneSet;
        action  new;
        source  setsToFaceZone;
        sourceInfo
        {
            faceSet     rotifFace;
            cellSet     rotif;
        }
    }
);

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