[HenningW]

Hi everyone. I have a case that uses sliding meshes (two oscillation airfoils using multiSolidBodyMotionFvMeshCoeffs). Unluckly the solution shows some asymmetry that does not make sense. This I want to create half the domain, run sHM and mirror the case to be sure that I have a symmetric mesh (at least for the timestep 0, later both airfoils oscillate in phase). It works fine for the mesh but it does not include a mirrored copy of the boundaries and cellZones which I need for the oscillation.

Do you guys have any idea how to get those as well? Or is there a setting that lets sHM create a symmetric mesh along a plane so I don't have to run mirrorMesh?

Here is my sHM file:

/*--------------------------------*- C++ -*----------------------------------*\
|       o          |                                                          |
|    o     o       | HELYX                                                  |
|   o   O   o      | Version: v2.1.1                                           |
|    o     o       | Web:     http://www.engys.com                            |
|       o          |                                                          |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version 2.0;
    format ascii;
    class dictionary;
    location system;
    object snappyHexMeshDict;
}

    castellatedMesh true;
    snap true;
    addLayers true;
    autoBlockMesh false;
    blockData ( 0.01 0);
    crackDetection false;
    crackTol 0.05;
    geometry
    {
        box_wake
        {
            type searchableBox;
            min ( 0.3 0.0 0 );
            max ( 2.0 1.4 0.5 );
        }

        box_right
        {
            type searchableBox;
            min ( -0.2 0.0 0.1 );
            max ( 1.0 1.2 0.7 );
        }

        airfoil_right.stl
        {
            type triSurfaceMesh;
            name airfoil_right;
            appendRegionName false;
        }

        zylinder_right.stl
        {
            type triSurfaceMesh;
            name slidingCellZoneRight;
            appendRegionName false;
        }

    }

    castellatedMeshControls
    {
        features
        (
        {
        file "right_bottom.eMesh";
        level 3;
      }
      {
        file "right_top.eMesh";
        level 3;
      }
      {
        file "right_TE.eMesh";
        level 3;
      }
        );
        refinementSurfaces
        {
            airfoil_right
            {
                level ( 3 3 );
            }
            slidingCellZoneRight
            {
                cellZoneInside inside;
                cellZone movingZoneRight;
                faceType boundary;
                faceZone movingZoneRight;
                level ( 3 3 );
            }

        }

        refinementRegions
        {
            box_wake
            {
                mode inside;
                levels (( 1E5 1 ));
            }

            box_right
            {
                mode inside;
                levels (( 1E5 1 ));
            }

        }

        locationInMesh ( 0.1 0.1 0.1 );
        maxLocalCells 100000000;
        maxGlobalCells 100000000;
        minRefinementCells 100;
        maxLoadUnbalance 0.10;
        nCellsBetweenLevels 3;
        resolveFeatureAngle -60.;
        featureRefineAngle 20.;
        refineSurfaceBoundary false;
        allowFreeStandingZoneFaces false;
        balanceThenRefine true;
        nGapRefinements 0;
        minZoneRegionSize 0;
        wrapper
        {
            wrap false;
            cutoff 0.02;
            sigma 3.0;
            volSources true;
            volDistance 1.0;
            meshInMM false;
            maxIter 200;
            writeFields false;
            invert false;
        }

    }

    snapControls
    {
        featureEdges
        {
        }

        nOuterIter 1;
        nPreFeatureIter 0;
        nSolveIter 10;
        nFeatureIter 60;
        globalFeatureEdges true;
        globalRegionSnap false;
        nSmoothPatch 2;
        tolerance 4.0;
        nRelaxIter 5;
        zoneFeatureSnapping true;
        directFeatureSnapping true;
        regionFeatureLines false;
        geometryFeatureLines true;
        snapSurfBoundary true;
        collapseTol 0.25;
    }

    addLayersControls
    {
        layers
        {
            airfoil_right
            {
                nSurfaceLayers 4;
                expansionRatio 1.5;
                fch 5.0E-4;
                grownUp false;
            }

            floor
            {
                nSurfaceLayers 6;
                expansionRatio 1.5;
                fch 5.0E-4;
            }

            ceiling
            {
                nSurfaceLayers 6;
                expansionRatio 1.5;
                fch 5.0E-4;
            }

            right
            {
                nSurfaceLayers 6;
                expansionRatio 1.5;
                fch 5.0E-4;
            }

        }

        relativeSizes true;
        expansionRatio 1.25;
        finalLayerThickness 0.4;
        minThickness 0.2;
    featureAngle 180; //Added later on
        featureAngleMerge 180;        // changed from 91
        featureAngleTerminate 180;    // changed from 91
        nRelaxIter 5;
        maxFaceThicknessRatio 2.0;
        maxThicknessToMedialRatio 0.3;
        minMedialAxisAngle 90;
        maxLayerIter 30;
        growConvexEdge true;
        growConcaveEdge true;
        growUpPatches true;
        preBalance false;
        writeVTK false;
        noErrors false;
        layerRecovery 1;
        growZoneLayers false;
        projectGrownUp 0.0;
    }

    meshQualityControls
    {
        maxNonOrtho 65;
        maxBoundarySkewness 20;
        maxInternalSkewness 4;
        maxConcave 80;
        minFlatness 0.5;
        minVol 1e-14;
        minTetQuality -1e30;
        minArea 1e-13;
        minTwist 0.05;
        minDeterminant 0.0001;
        minFaceWeight 0.05;
        minVolRatio 0.01;
        minTriangleTwist -0.99;
        nSmoothScale 10;
        errorReduction 0.75;
        faceFaceCells true;
    }

    debug 0;
    mergeTolerance 1E-6;
    repatchRegions
    {
        movingPatchRight
        {
            location ( 0.0 0.1 0.35 );
            excludePatches ( slidingCellZoneRight slidingCellZoneRight_slave );
            zone movingZoneRight;
        }
    }

Thanks for your help.

Henning

Here is a picture of (a part of) the mirrored mesh without the zones and boundaries at and around the upper airfoil:

[chegdan]

Henning,

First off, welcome to the forum. Secondly, you have numerous approaches to solve your problem:

1. topoSet:On your mirrored mesh you can create a cellZone of your region you want to move using topoSet and then continue from there. There is an example topoSetDict in the topoSet application directory. If you create a cellSet, just make sure to use setsToZones to create the cellZone.
2. Mirror your surfaces and remesh in a larger domain: For this method, you can make a copy of surfaces to encompass the new mirrored surfaces (either use a CAD software, Blender, etc. to make it or simply copy the surface and then rotate and/or translate the surface with surfaceTransformPoints); increase the size of your cellZones (or add more) to encompass your new mirrored surfaces; and remesh on a larger domain.

I would try the first option, though I'm not sure how well mirrorMesh turned out since your images did not appear in your post. Good luck and I hope this helps.

[HenningW]

Hi Dan,

tanks a lot for your response. I think I tried your second approach by generating a large domain and putting in 2 stl files symmetric to my x-axis. After that I ran sHM and pimpleDyMFoam. Unluckly, those are the results that are not symmetric and why I wanted to try mirrorMesh, because I am not 100% suer that the mesh is symmetric along the x-axis in that approach.

I will take a look at the first approach. However, I have never done that and might ask a few more questions about topoSet soon =)

However, thanks again for your help

Henning