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moveDynamicMesh - bad cells after motion

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Old   December 8, 2014, 07:46
Default moveDynamicMesh - bad cells after motion
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Petr Furmanek
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Nice Monday afternoon to all!

Recently I've run into a problem with moveDynamicMesh. I'd like to perform a simple flutter analysis with openfoam. I'm using the standard NACA 0012 profile, which is attached to en elastic axis EA (i.e. in 2D it is a point located on the profiles chord) and can oscillate around this axis and vibrate in vertical direction.
In order to place the profile into right initial position (e.g. Alpha_init = 3, h_init = -0.01m) I'm using moveDynamicMesh solver and mesh created with GridPro. With this mesh I can perform steady simulations without any problem (the only error checkMesh reports are highAspectRatio cells, which is normal. However, if I add prescribed motion it always ends with many bad cells (no matter what time-step or tolerance parameters I use)

Code:
Checking geometry...
    Overall domain bounding box (-2.69997 -3 0) (1.5 3 0.015)
    Mesh (non-empty, non-wedge) directions (1 1 0)
    Mesh (non-empty) directions (1 1 0)
    All edges aligned with or perpendicular to non-empty directions.
    Boundary openness (-1.83973e-18 1.14303e-19 7.89943e-15) OK.
 ***High aspect ratio cells found, Max aspect ratio: 1265.93, number of cells 6
  <<Writing 6 cells with high aspect ratio to set highAspectRatioCells
    Minimum face area = 3.73703e-09. Maximum face area = 0.00237795.  Face area magnitudes OK.
 ***Zero or negative cell volume detected.  Minimum negative volume: -2.45686e-09, Number of negative volume cells: 5
  <<Writing 5 zero volume cells to set zeroVolumeCells
    Mesh non-orthogonality Max: 179.673 average: 7.00679
   *Number of severely non-orthogonal (> 70 degrees) faces: 83.
 ***Number of non-orthogonality errors: 9.
  <<Writing 92 non-orthogonal faces to set nonOrthoFaces
 ***Error in face pyramids: 28 faces are incorrectly oriented.
  <<Writing 24 faces with incorrect orientation to set wrongOrientedFaces
    Max skewness = 0.92386 OK.
    Coupled point location match (average 0) OK.

Failed 4 mesh checks.
Problematic cells are located on and behind the trailing edge. The motion itself is prescribed in a standard way using the pointDisplacement file in 0 directory

Code:
boundaryField
{
     ".*"
     {
         type            fixedValue;
         value           uniform (0 0 0);
     }
     
    wing
    {
        type            angularOscillatingDisplacement;
        axis            (0 0 1);
        origin          (0.12 0 0.0075);
        angle0          0;
        amplitude       -0.05235987755983; //rad
        omega           3.14159; //rad/s
        value           uniform (0 0 0);
    }

    "(front|back)"
    {
        type empty;
    }

}
dynamicMeshDict in the constant directory

Code:
dynamicFvMesh      dynamicMotionSolverFvMesh;

motionSolverLibs ("libfvMotionSolvers.so");

solver displacementLaplacian;
// solver velocityComponentLaplacian z;

displacementLaplacianCoeffs
{
    diffusivity quadratic inverseDistance 1(wing);
}
and this solver for point motion in the fvSolution

Code:
    cellDisplacement
    {
        solver          GAMG;
        tolerance       1e-5;
        relTol          0.0;
        smoother        DICGaussSeidel;
        cacheAgglomeration true;
        nCellsInCoarsestLevel 10;
        agglomerator    faceAreaPair;
        mergeLevels     1;
    }
Do you have any idea, what am I doing wrong or how to move the profile without obtaining errors?
Attached Images
File Type: jpg mesh_time0.0_1.jpg (37.9 KB, 12 views)
File Type: jpg mesh_time0.5_1.jpg (37.9 KB, 10 views)
File Type: png mesh_time0.5_treilingEdge_1.png (51.6 KB, 13 views)
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