[arukan]

Hello everyone,

I'm simulating a stacked propeller using cyclicAMI bc in OpenFoam 9.
I have successfully completed a simulation with a coarser mesh, however, I have problems with the simulation after refinement. I have noticed that the AMI weight goes to 0 at every timestep.
I used blockMesh for the domain and then applied shM to AMI and fans. To create AMI I used createBaffles utility.
I had this problem before and was able to overcome this by adjusting snappyHexMesh settings (however I am not exactly sure what helped), but not at every time step. The only thing I changed is increased the refinementSurfaces level for fan1 and fan2 from (3 4) to (4 5). Here is my sHM dict:

/*--------------------------------*- C++ -*----------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     | Website:  https://openfoam.org
    \\  /    A nd           | Version:  9
     \\/     M anipulation  |
\*---------------------------------------------------------------------------*/
FoamFile
{
    format      ascii;
    class       dictionary;
    object      snappyHexMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

castellatedMesh true;
snap            true;
addLayers       true;

geometry
{
    AMI.stl
    {
        type triSurfaceMesh;
        name AMI;
    }
    fan1.stl
    {
        type triSurfaceMesh;
        name fan1;
    }
	fan2.stl
    {
        type triSurfaceMesh;
        name fan2;
    }
    refinementBox
    {
        type    searchableBox;
        min     (1.8 -0.5 -0.5);
        max     (3 0.5 0.5);
    }

};



castellatedMeshControls
{
    maxLocalCells 100000;
    maxGlobalCells 7000000;
    minRefinementCells 0;
    maxLoadUnbalance 0.10;
    nCellsBetweenLevels 3;

    features
    (
        {
            file "fan1.eMesh";
            level 4;
        }
		{
            file "fan2.eMesh";
            level 4;
        }
		{
            file "AMI.eMesh";
            level 4;
        }
    );


    refinementSurfaces
    {
        AMI
        {
            level (3 3);
	    cellZone rotating_zone;
	    faceZone rotating_zone;
	    cellZoneInside inside;
        }
		fan1
        {
            level (4 5);
        }
		fan2
        {
            level (4 5);
        }
    }

    resolveFeatureAngle 30;

    refinementRegions
    {
        AMI
        {
            mode    inside;
            level   2;
        }
		refinementBox
		{
			mode inside;
			level 1;
		}
    }


    locationInMesh (0.61 0 0);
    allowFreeStandingZoneFaces true;
}



snapControls
{

    nSmoothPatch 3;
    tolerance 4.0;
    nSolveIter 50;
    nRelaxIter 5;
	
        //nFeatureSnapIter 25;
        implicitFeatureSnap true;
        explicitFeatureSnap false;
        multiRegionFeatureSnap false;
}



// Settings for the layer addition.
addLayersControls
{
    relativeSizes true;

    layers
    {
        "(fan).*"
        {
            nSurfaceLayers 7;
        }
    }

    expansionRatio 1.0;
    finalLayerThickness 0.3;
    minThickness 0.1;
    nGrow 0;
    featureAngle 60;
    nRelaxIter 3;
    nSmoothSurfaceNormals 1;
    nSmoothNormals 3;
    nSmoothThickness 2;
    maxFaceThicknessRatio 0.5;
    maxThicknessToMedialRatio 0.3;
    minMedianAxisAngle 90;
    nBufferCellsNoExtrude 0;
    nLayerIter 20;
}

meshQualityControls
{
    maxNonOrtho 65;
    maxBoundarySkewness 20;
    maxInternalSkewness 4;
    maxConcave 80;
    minFlatness 0.5;
    minVol 1e-13;
    minTetQuality 1e-30;
    minArea -1;
    minTwist 0.02;
    minDeterminant 0.001;
    minFaceWeight 0.02;
    minVolRatio 0.01;
    minTriangleTwist -1;
    // Advanced

    //- Number of error distribution iterations
    nSmoothScale 4;
    //- Amount to scale back displacement at error points
    errorReduction 0.75;
}


// Advanced

// Merge tolerance. Is fraction of overall bounding box of initial mesh.
// Note: the write tolerance needs to be higher than this.
mergeTolerance 1e-6;


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

I found this post :Cyclic AMI patch minimum weight goes to zero
and tried to follow Artur's advide. But I think it is not applicable to my case, since AMI goes to 0 at every time step. Increasing FeatureSnapIter gives skewed faces in the propeller so I disabled it. I also tried turning on implicitFeatureSnap as was suggested in the post, but it did not help.

checkMesh does not give any errors. The AMI patches look identical in paraview. I attached the clip of the rotating zone.

Any help would be greatly appreciated!
AMI1.jpg

AMI2.jpg

rotating_zone.jpg