[estang]

I want to mesh a pipe and a fluid for conjugated heat transfer just to test the solver and learning how to use it. But my result is not snapped to the stl. I already played with the settings, i increased iterations in the snapControls and refined the mesh at the surface in castellatedMeshControls.

The images illustrate the fluiddomain and the soliddomain.

castellatedMesh   true;
snap              true;
addLayers         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
{
    FluidDomain.stl
    {
        type triSurfaceMesh;
        name fluid;
        faceZone fluidFaces;
        cellZone fluidZone;
        cellZoneInside insidePoint;
        insidePoint (-10 0 0);
    }
    SolidDomain.stl
    {
        type triSurfaceMesh;
        name solid;
        faceZone solidFaces;
        cellZone solidZone;
        cellZoneInside insidePoint;
        insidePoint (-10 0.240 0);
    }
};



// 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 2000000;

    // 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 4444000;

    // 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 0.0;


    // Number of buffer layers between different levels.
    // 1 means normal 2:1 refinement restriction, larger means slower
    // refinement.
    nCellsBetweenLevels 5;



    // 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 "FluidDomain.eMesh";
            level 4;
        }
        {
            file "SolidDomain.eMesh";
            level 4;
        }
    );



    // 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
    {    
    fluid
        {

            faceZone fluidFaces;
            cellZone fluidZone;
            cellZoneInside insidePoint;
            insidePoint (-10 0 0);
        
        level (2 2);
        }
        solid
        {
            faceZone solidFaces;
            cellZone solidZone;
            cellZoneInside insidePoint;
            insidePoint (-10 0.240 0);

        level (2 2);
        }
    }

    // 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
    {

    }


    // 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 (-10 0 0);


    // 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 10;

    //- Relative distance for points to be attracted by surface feature point
    //  or edge. True distance is this factor times local
    //  maximum edge length.
    tolerance 1.2;

    //- Number of mesh displacement relaxation iterations.
    nSolveIter 200;

    //- Maximum number of snapping relaxation iterations. Should stop
    //  before upon reaching a correct mesh.
    nRelaxIter 10;

    // Feature snapping

        //- Number of feature edge snapping iterations.
        //  Leave out altogether to disable.
        nFeatureSnapIter 10;

        //- Detect (geometric only) features by sampling the surface
        //  (default=false).
        implicitFeatureSnap false;

        //- Use castellatedMeshControls::features (default = true)
        explicitFeatureSnap true;

        //- Detect points on multiple surfaces (only for explicitFeatureSnap)
        multiRegionFeatureSnap true;
}

[ssss]

Try to increase the background mesh it is too coarse I think

[estang]

Thank you for your help.

I increased the level of surface Refinement to 4. The result is attached to this post.

Do you think the axial coarseness makes a problem?

The meshing finished with 95219 faces of non-orthogonality > 65 degrees.

[ssss]

I mean, that you need to refine more the background mesh, this is the background you do with blockMesh before usign snappyHexMesh

[student666]

Did you check the surface quality with OF tools: surfaceCheck surfaceClean surfaceOrient?

[estang]

hi student666,

i checked it with surfaceCheck and it's fine.

[student666]

Well, i suggest you to look for some help here https://sites.google.com/site/snappywiki/snappyhexmesh

Or you try to mesh two domains jndividually, then merging them: mergeMeshes masterCase slaveCase -overwrite

Bye

[estang]

Thank you i will try it