2 2

Next: Model setting without an Up: Alternative formulation Previous: Alternative formulation   Contents   Index

Running SnappyHexMesh - Rotor Region

Utility snappyHexMesh refines background mesh in direction to the surface model, reading set-up from system/snappyHexMeshDict:


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
        type        triSurfaceMesh;
        name        t-housing;
        type        triSurfaceMesh;
        name        t-wheel;
        type        triSurfaceMesh;
        name        interface;

// Settings for the castellatedMesh generation.

    // 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 120000000;

    // 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 150000000;

    // 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 1;

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

    // Specifies a level for any cell intersected by its edges.
    // This is a featureEdgeMesh, read from constant/triSurface for now.
//      {
//          file        "t-wheel.eMesh";
//          level       6;
//      }
//      { 
//          file        "t-housing.eMesh";
//          level       4;
//      }
            file        "t-housing_interface-t1_intersection.eMesh";
            level       5;

    // 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.

            level       (4 6);
            level       (4 6);
	    level       (5 5);

    // 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.


    // 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 (0. 0. 449.);

    // 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;

Create the mesh running snappyHexMesh utility:

$ \color{white} \gg$ snappyHexMesh

In order to reduce bandwidth and speed up computation on the generated rotor mesh, it is convenient to use renumberMesh utility using following command:

$ \color{white} \gg$ renumberMesh -latestTime

When finished, check the mesh running checkMesh and view the mesh in paraview:

$ \color{white} \gg$ checkMesh -latestTime
$ \color{white} \gg$ paraFoam


Figure: Rotor mesh view.

The final mesh is located in the directory called by number. Copy mesh to constant/polyMesh directory and remove unnecessary mesh directories:

$ \color{white} \gg$ cp -rf 3/polyMesh/* constant/polyMesh/
$ \color{white} \gg$ rm -rf 1 2 3