[BenGher]

Hello foamers,

I am trying to convert a mesh from fluent to openfoam, and I am blocked at the following error:

Create time

Dimension of grid: 3
Number of points: 6926048
Number of faces: 12597122
Number of cells: 3106054
PointGroup: 11562 start: 0 end: 42135.  Reading points...done.
PointGroup: 18 start: 42136 end: 42365.  Reading points...done.
PointGroup: 29 start: 42366 end: 42387.  Reading points...done.
PointGroup: 31 start: 42388 end: 42409.  Reading points...done.
PointGroup: 33 start: 42410 end: 42429.  Reading points...done.
PointGroup: 35 start: 42430 end: 42451.  Reading points...done.
PointGroup: 37 start: 42452 end: 42471.  Reading points...done.
PointGroup: 39 start: 42472 end: 42493.  Reading points...done.
PointGroup: 55 start: 42494 end: 43408.  Reading points...done.
PointGroup: 75 start: 43409 end: 44884.  Reading points...done.
PointGroup: 95 start: 44885 end: 45538.  Reading points...done.
PointGroup: 103 start: 45539 end: 45687.  Reading points...done.
PointGroup: 11624 start: 45688 end: 310456.  Reading points...done.
PointGroup: 11633 start: 881799 end: 6926047.  Reading points...done.
PointGroup: 11640 start: 310457 end: 319728.  Reading points...done.
PointGroup: 11897 start: 319729 end: 881798.  Reading points...done.
FaceGroup: 11597 start: 0 end: 275917.  Reading mixed faces...done.
FaceGroup: 11572 start: 275918 end: 277552.  Reading mixed faces...done.
FaceGroup: 11571 start: 277553 end: 279196.  Reading mixed faces...done.
FaceGroup: 11570 start: 279197 end: 280584.  Reading mixed faces...done.
FaceGroup: 11569 start: 280585 end: 282229.  Reading mixed faces...done.
FaceGroup: 11568 start: 282230 end: 283974.  Reading mixed faces...done.
FaceGroup: 11567 start: 283975 end: 285625.  Reading mixed faces...done.
FaceGroup: 11631 start: 376428 end: 12597121.  Reading mixed faces...done.
FaceGroup: 98 start: 285626 end: 286929.  Reading uniform faces...done.
FaceGroup: 78 start: 286930 end: 289877.  Reading uniform faces...done.
FaceGroup: 58 start: 289878 end: 291703.  Reading uniform faces...done.
FaceGroup: 27 start: 291704 end: 291771.  Reading uniform faces...done.
FaceGroup: 26 start: 291772 end: 291853.  Reading uniform faces...done.
FaceGroup: 25 start: 291854 end: 291921.  Reading uniform faces...done.
FaceGroup: 24 start: 291922 end: 291999.  Reading uniform faces...done.
FaceGroup: 23 start: 292000 end: 292081.  Reading uniform faces...done.
FaceGroup: 21 start: 292082 end: 292159.  Reading uniform faces...done.
FaceGroup: 2 start: 292160 end: 376427.  Reading uniform faces...done.
CellGroup: 11629 start: 0 end: 3106053 type: 1
--> FOAM Warning : Found unknown block of type: "71"
    on line 19523259
--> FOAM Warning : Found unknown block of type: "71"
    on line 19788032
--> FOAM Warning : Found unknown block of type: "71"
    on line 19789687
--> FOAM Warning : Found unknown block of type: "71"
    on line 19791436
--> FOAM Warning : Found unknown block of type: "71"
    on line 19793085
--> FOAM Warning : Found unknown block of type: "71"
    on line 19794477
--> FOAM Warning : Found unknown block of type: "71"
    on line 19796125
--> FOAM Warning : Found unknown block of type: "71"
    on line 19797764
Zone: 11629 name: fluid-region-1 type: fluid.  Reading zone data...done.
Zone: 2 name: origin-glider type: wall.  Reading zone data...done.
Zone: 21 name: origin-tunnel-zmax type: wall.  Reading zone data...done.
Zone: 23 name: origin-tunnel-zmin type: wall.  Reading zone data...done.
Zone: 24 name: origin-tunnel-ymax type: wall.  Reading zone data...done.
Zone: 25 name: origin-tunnel-xmin type: wall.  Reading zone data...done.
Zone: 26 name: origin-tunnel-ymin type: wall.  Reading zone data...done.
Zone: 27 name: origin-tunnel-xmax type: wall.  Reading zone data...done.
Zone: 58 name: fine type: wall.  Reading zone data...done.
Zone: 78 name: medium type: wall.  Reading zone data...done.
Zone: 98 name: coarse type: wall.  Reading zone data...done.
Zone: 11631 name: interior--fluid-region-1 type: interior.  Reading zone data...done.
Zone: 11567 name: tunnel-zmax type: velocity-inlet.  Reading zone data...done.
Zone: 11568 name: tunnel-xmax type: velocity-inlet.  Reading zone data...done.
Zone: 11569 name: tunnel-ymin type: velocity-inlet.  Reading zone data...done.
Zone: 11570 name: tunnel-xmin type: pressure-outlet.  Reading zone data...done.
Zone: 11571 name: tunnel-ymax type: velocity-inlet.  Reading zone data...done.
Zone: 11572 name: tunnel-zmin type: velocity-inlet.  Reading zone data...done.
Zone: 11597 name: glider type: wall.  Reading zone data...done.
--> FOAM Warning : Found unknown block of type: "73"
    on line 20063727

FINISHED LEXING

Creating patch 0 for zone: 11597 name: glider type: wall
Creating patch 1 for zone: 11572 name: tunnel-zmin type: velocity-inlet
Creating patch 2 for zone: 11571 name: tunnel-ymax type: velocity-inlet
Creating patch 3 for zone: 11570 name: tunnel-xmin type: pressure-outlet
Creating patch 4 for zone: 11569 name: tunnel-ymin type: velocity-inlet
Creating patch 5 for zone: 11568 name: tunnel-xmax type: velocity-inlet
Creating patch 6 for zone: 11567 name: tunnel-zmax type: velocity-inlet
Creating patch 7 for zone: 98 name: coarse type: wall
Creating patch 8 for zone: 78 name: medium type: wall
Creating patch 9 for zone: 58 name: fine type: wall
Creating patch 10 for zone: 27 name: origin-tunnel-xmax type: wall
Creating patch 11 for zone: 26 name: origin-tunnel-ymin type: wall
Creating patch 12 for zone: 25 name: origin-tunnel-xmin type: wall
Creating patch 13 for zone: 24 name: origin-tunnel-ymax type: wall
Creating patch 14 for zone: 23 name: origin-tunnel-zmin type: wall
Creating patch 15 for zone: 21 name: origin-tunnel-zmax type: wall
Creating patch 16 for zone: 2 name: origin-glider type: wall
Creating cellZone 0 name: fluid-region-1 type: fluid
Creating faceZone 0 name: interior--fluid-region-1 type: interior
faceZone from Fluent indices: 376428 to: 12597121 type: interior
patch 0 from Fluent indices: 0 to: 275917 type: wall
patch 1 from Fluent indices: 275918 to: 277552 type: velocity-inlet
patch 2 from Fluent indices: 277553 to: 279196 type: velocity-inlet
patch 3 from Fluent indices: 279197 to: 280584 type: pressure-outlet
patch 4 from Fluent indices: 280585 to: 282229 type: velocity-inlet
patch 5 from Fluent indices: 282230 to: 283974 type: velocity-inlet
patch 6 from Fluent indices: 283975 to: 285625 type: velocity-inlet
patch 7 from Fluent indices: 285626 to: 286929 type: wall
patch 8 from Fluent indices: 286930 to: 289877 type: wall
patch 9 from Fluent indices: 289878 to: 291703 type: wall
patch 10 from Fluent indices: 291704 to: 291771 type: wall
patch 11 from Fluent indices: 291772 to: 291853 type: wall
patch 12 from Fluent indices: 291854 to: 291921 type: wall
patch 13 from Fluent indices: 291922 to: 291999 type: wall
patch 14 from Fluent indices: 292000 to: 292081 type: wall
patch 15 from Fluent indices: 292082 to: 292159 type: wall
patch 16 from Fluent indices: 292160 to: 376427 type: wall


--> FOAM FATAL ERROR: 
Illegal cell label -1 in neighbour addressing for face 12506320

    From function void Foam::polyMesh::initMesh()
    in file meshes/polyMesh/polyMeshInitMesh.C at line 64.

FOAM exiting

I looked a bit on the forum and the closest topic I could find were those:

1. Illegal cell label -1, error in mesh-conversion, icem
2. Error by importing .msh format to openfoam

However 1) is quite old and using Icem instead of fluent meshing, and I tried to save as an ascii .cas as suggested in 2) but the error remains.

Would anyone have an idea on how to solve this?

EDIT: Looking at the source code of polyMeshInitMesh.C it seems there is an issue with the cell owning face 12506320, but I don't understand it nor how to fix it.

#include "polyMesh.H"

// * * * * * * * * * * * * * Private Member Functions  * * * * * * * * * * * //

void Foam::polyMesh::initMesh()
{
    DebugInFunction << "initialising primitiveMesh" << endl;

    // For backward compatibility check if the neighbour array is the same
    // length as the owner and shrink to remove the -1s padding
    if (neighbour_.size() == owner_.size())
    {
        label nInternalFaces = 0;

        forAll(neighbour_, facei)
        {
            if (neighbour_[facei] == -1)
            {
                break;
            }
            else
            {
                nInternalFaces++;
            }
        }

        neighbour_.setSize(nInternalFaces);
    }

    label nCells = -1;

    forAll(owner_, facei)
    {
        if (owner_[facei] < 0)
        {
            FatalErrorInFunction
                << "Illegal cell label " << owner_[facei]
                << " in neighbour addressing for face " << facei
                << exit(FatalError);
        }
        nCells = max(nCells, owner_[facei]);
    }

[BenGher]

Update

I tried to use the simpler version "FluentMeshToFoam", but end up having the same problem. Currently trying to set up a really simple case (3D sphere) to see if I can reproduce the error, or if it comes from the .stl.

In the meantime if anyone has any tips, or direction for me to look into, I would be glad.

PS: I am aware that the post could be better suited to the "meshing" section of this forum, but I can't delete or move it, and don't want to double post.

[geth03]

are you sure that you did export a volume mesh from ansys?
it looks like you did export a surface mesh.

[BenGher]

Originally Posted by geth03

are you sure that you did export a volume mesh from ansys?
it looks like you did export a surface mesh.

Hi,

I used File > Write > Mesh --> Files of type: Legacy Compressed Mesh Files (*.msh.gz), "write binary files" unticked, so I think so.

I "gzip -d meshfile.msh.gz" in order to get the meshfile.msh...could there be an issue in the decompressing step? I just tried with another mesh, to be certain, and still have the exact same issue.

[bumble]

Hi Ben,
I am facing the same error when I import mesh from ICEM to openfoam. Have you found the actual reason for this?

[BenGher]

Hello,

Unfortunately not, which led me to consider other options than Fluent meshing.

I am not familiar with ICEM, but a guy with a similar problem as yours posted this , and it seems he forgot to import/export the volume mesh.

Hope it helps, don't hesitate to share the answer if you find it

[bumble]

Hi,
I actually shifted to the Mesh module of ANSYS from ICEM. I didn't get the error when I imported it to OpenFOAM. I came across the thread you mentioned, I think it is one of the reasons to get this error.

In the process, I discovered that you could do a check mesh in the ICEM or probably in Mesh (ANSYS module) too. I used to have some penetrating cells in ICEM, and if I import the same mesh in OpenFOAM, I get the error.

Again, I am not sure the exact reason, but there are probably multiple factors.

[cweisheng]

Not sure if you solved this. I was also caught with some of the errors while attempting to use a fluent mesh with "internal" type face zones that enclose a cell zone intended as a porous zone. The most important things I found:
- use Prepare for Solve in Fluent Meshing to remove the unnecessary parts of the mesh
- export as .msh while unchecking Binary
- run fluent3DMeshToFoam (remember to scale it if your Fluent mesh is in mm and OF parameters are in SI). The utility should ignore the "internal" zones. Check your constant/PolyMesh files to be sure.