[Bourstras]

Hello everyone, I allow to ask you if you could helped me. So, I'm working on a project where I have a dam with a breach.
My goal is to define a mesh arround this dam in a channel with an inlet and oulet. I have define the structure to start the mesh and the inlet, outlet and the dam are define also in the structure.
After that, I use ./Allrun command with :

runApplication blockMesh
runApplication decomposePar
runParallel snappyHexMesh -overwrite
runApplication reconstructParMesh -constant
runApplication setFields
checkMesh

Then, I launch this command above (./Allrun), I have an error during the process of snappyHexMesh because I have this error :
Signal: Floating point exception (8)
Signal code: (-6)

So the process stops working and the final check mesh explaines me this 7 errors :

Checking geometry...
Overall domain bounding box (-2.27 -8.76767e-200 -3.5072e-13) (3.53 0.393 0.5)
Mesh has 3 geometric (non-empty/wedge) directions (1 1 1)
Mesh has 3 solution (non-empty) directions (1 1 1)
Boundary openness (4.74463e-20 -5.69356e-19 2.78352e-18) OK.
***High aspect ratio cells found, Max aspect ratio: 1.77791e+150, number of cells 31190
<<Writing 31190 cells with high aspect ratio to set highAspectRatioCells
***Zero or negative face area detected. Minimum area: 0
<<Writing 112 zero area faces to set zeroAreaFaces
***Zero or negative cell volume detected. Minimum negative volume: -0.219996, Number of negative volume cells: 20255
<<Writing 20255 zero volume cells to set zeroVolumeCells
Mesh non-orthogonality Max: 179.89 average: 89.888
*Number of severely non-orthogonal (> 70 degrees) faces: 65017.
***Number of non-orthogonality errors: 60609.
<<Writing 125626 non-orthogonal faces to set nonOrthoFaces
***Error in face pyramids: 120727 faces are incorrectly oriented.
<<Writing 96682 faces with incorrect orientation to set wrongOrientedFaces
***Max skewness = 2.69169e+134, 11886 highly skew faces detected which may impair the quality of the results
<<Writing 11886 skew faces to set skewFaces
Coupled point location match (average 0) OK.

Failed 7 mesh checks.

Have you any idea why have I this isue ?

[AtoHM]

Hello Bourstras,


There is no way diagnosing the problem with the provided information. The error shown is a floating point error which can be caused by anything. The obvious spot to look first is inside the snappyHexMesh or blockMesh dictionaries. You can add these here inside a message. Also the way the geometry files (stl) are assembled can be problematic, if it is not proprietary, you may attach this to the post too.


Greetings!

[Bourstras]

Ok well, the blockMesh and snappyHexMesh are :

/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: dev |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
object blockMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

scale 0.001;

vertices
(
(-2270 0 0) //0
(3530 0 0) //1
(3530 393 0) //2
(-2270 393 0) //3
(-2270 0 500) //4
(3530 0 500) //5
(3530 393 500) //6
(-2270 393 500) //7


);

blocks
(
hex (0 1 2 3 4 5 6 7) (50 30 30) simpleGrading (1 1 20)
);

edges
(
);

boundary
(
bottom
{
type wall;
faces
(
(0 3 2 1)
);
}

walls
{
type wall;
faces
(
(0 1 5 4)
(3 7 6 2)
);
}

atmin
{
type patch;
faces
(
(0 4 7 3)
);
}

atmout
{
type patch;
faces
(
(1 2 6 5)
);
}

atmosphere
{
type patch;
faces
(
(7 6 5 4)
);
}
);

mergePatchPairs
(
);

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

And

/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: dev |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
object snappyHexMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

#includeEtc "caseDicts/mesh/generation/snappyHexMeshDict.cfg"

castellatedMesh on;
snap on;
addLayers on;

geometry
{
dambreach
{
type triSurfaceMesh;
file "piv_modelo_3D_metros.stl";
}

inlet
{
type searchableBox;
min (-2.280 0 0);
max (-2.270 0.393 0.300);
}

outlet
{
type searchableCylinder;
point1 (3.060 0.1975 0);
point2 (3.060 0.1975 -0.100);
radius 0.125;
}

box
{
type searchableBox;
min (0 0 0);
max (1.55 0.393 0.300);
}

}

castellatedMeshControls
{
features
(
);

refinementSurfaces
{
dambreach
{
level (2 2);
}

inlet
{
level (2 2);
}

outlet
{
level (2 2);
}
}

refinementRegions
{
dambreach
{
mode inside;
levels ((0.1 2));
}

box
{
mode inside;
levels ((2 2));
}
}

locationInMesh (-2.2 0.1 0.1);
maxLocalCells 100000;
maxGlobalCells 2000000;
minRefinementCells 1;
maxLoadUnbalance 0.10;
allowFreeStandingZoneFaces false;
nCellsBetweenLevels 2;
resolveFeatureAngle 30;
}

snapControls
{
nSmoothPatch 3;
tolerance 4.0;
nSolveIter 30;
nRelaxIter 5;

nFeatureSnapIter 10;
implicitFeatureSnap false;
explicitFeatureSnap true;
multiRegionFeatureSnap false;
}

addLayersControls
{
layers
{
"dambreach.*"
{
nSurfaceLayers 3;
}
}

relativeSizes true;
//firstLayerThickness 0.3;
//thickness 0.3;
finalLayerThickness 0.3;
minThickness 0.1;
expansionRatio 1.0;

nGrow 1;
featureAngle 60;
nSmoothSurfaceNormals 1;
nSmoothNormals 3;
nSmoothThickness 10;
maxFaceThicknessRatio 0.5;
maxThicknessToMedialRatio 0.3;
minMedianAxisAngle 90;
nBufferCellsNoExtrude 0;
nLayerIter 50;
nRelaxIter 3;
slipFeatureAngle 30;

}

meshQualityControls
{

maxNonOrtho 65;
maxBoundarySkewness 20;
maxInternalSkewness 4;
maxConcave 80;
minFlatness 0.5;
minVol 1e-13;
minTetQuality 1e-13;
minArea -1;
minTwist 0.5;
minDeterminant 0.001;
minFaceWeight 0.05;
minVolRatio 0.01;
minTriangleTwist -1;
nSmoothScale 4;
errorReduction 0.75;
relaxed;

}


writeFlags
(
scalarLevels
layerSets
layerFields
);

mergeTolerance 1e-6;

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

[AtoHM]

So far so good. The first thing that pops up to me is, that you seem to be attempting to create boundary conditions with searchableBox and searchableCylinder sources, which are both 3d objects. That won't work, or probably not as intended. Usually, you provide the boundary faces inside the stl as named solids. With the current setup, snappy snaps to the faces of these 3d regions and removes the cells (depending on where your locationInMesh is) outside or inside of them.

However, thats maybe not causing the actuall error. Can you provide the whole log of the snappyHexMesh run to exactly see where it fails (sorry, I should have asked for that in the first response too).

[Bourstras]

Yes of course.

[AtoHM]

Unfortunately not much to get from this. However, at the start it states that

Surface dambreach is closed but has inconsistent face orientation

My best guess is that your geometry is faulty but without seeing it, I am afraid we cannot say for sure.

[Bourstras]

Hello,

According to you, the problem is the geometry of the dam, but how do I know that the geometry is faulty?:confus:

[AtoHM]

I quoted a piece of the log file you provided, so this is at least a glue to something related to the geometry. It appears to be having inconsistent face normals. I never had to deal with this kind of error so I cannot say for sure if this is the source of the issue.
You need to work piece by piece to find the issue. You can use the surfaceCheck utility of OpenFOAM to check the stl again. It might tell you something more or the same thing. If that does not help, look that the blockMesh is correctly created (maybe it creates some really bad cells and then everything goes south in snappy?). Step by step ...
Good luck.