[AMR96]

Hello,

I would like to simulate the flow around a formula car in OpenFoam, I have dealt with the geometry in Ansys SpaceClaim and have generated a sample mesh with Fluent. I'm aware that the mesh is not perfect, my goal at the moment is to see which type of mesh is most suitable for the simulation (tetrahedral or polyhedral).

I have a few doubts and problems at certain stages of exporting and checking the mesh in OpenFoam:

1. Once I export the .msh file from Fluent and use the Fluent3DMeshToFoam command, I get the following warning during the conversion process:

FOAM Warning : Found unknown block of type: "11"
on line 44406446

The latter happens a dozen times during the process but at the end the mesh is converted. I would like to know if this is something serious or not and what it means?

2. When I run the checkMesh command, I get the following messages which seem to be not normal:

a. ***Unused points found in the mesh, number unused by faces: 38119 number unused by cells: 38119
<<Writing 38119 unused points to set unusedPoints
For this case, I used a feature in Fluent which allowed me to delete all the unused nodes. However, OpenFoam still finds unused points in the mesh. I'm not sure why this is happening.
I would like to know what can cause having unused points and if it will affect the simulation results?
Or how to remove them within the FOAM environment.

b. <<Writing 3222 unordered faces to set upperTriangularFace
For this case, I tried running the renumberMesh command as suggested in other forums but the result of checkMesh didn't change. Could these faces be problematic during the simulation or can I ignore them?

Below is the checkMesh result which says, failed 2 checks, I believe that is due to the non-orthogonal faces and high skewness, please correct me if I'm wrong.

Note: If I use Ansys Meshing to generate a tet mesh, the checkMesh finishes without any problems mentioned in the post.

Many thanks in advance.

/*---------------------------------------------------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2206                                  |
|   \\  /    A nd           | Website:  www.openfoam.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
Build  : 34e226dfe3-20211220 OPENFOAM=2206 version=v2206
Arch   : "LSB;label=32;scalar=64"
Exec   : C:\Program Files\ESI-OpenCFD\OpenFOAM\v2206\msys64\home\ofuser\OpenFOAM\OpenFOAM-v2206\platforms\win64MingwDPInt32Opt\bin\checkMesh.exe
Date   : Jun 08 2023
Time   : 18:01:50
Host   : LAPTOP-CDITD2NN
PID    : 17492
I/O    : uncollated
Case   : C:/EPFL/test2
nProcs : 1
trapFpe: Floating point exception trapping enabled (FOAM_SIGFPE).
fileModificationChecking : Monitoring run-time modified files using timeStampMaster (fileModificationSkew 5, maxFileModificationPolls 20)
allowSystemOperations : Allowing user-supplied system call operations

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Create time

Create mesh for time = 0

Time = 0

Mesh stats
    points:           44402183
    faces:            65928311
    internal faces:   64421568
    cells:            12900186
    faces per cell:   10.104496
    boundary patches: 4
    point zones:      0
    face zones:       1
    cell zones:       1

Overall number of cells of each type:
    hexahedra:     23517
    prisms:        5085
    wedges:        2135
    pyramids:      102
    tet wedges:    33
    tetrahedra:    256
    polyhedra:     12869058
    Breakdown of polyhedra by number of faces:
        faces   number of cells
            4   8
            5   105
            6   596
            7   795320
            8   6215048
            9   631011
           10   683831
           11   666849
           12   615820
           13   816841
           14   907858
           15   746620
           16   460946
           17   216953
           18   80062
           19   23775
           20   5916
           21   1252
           22   195
           23   42
           24   10

Checking topology...
    Boundary definition OK.
    Cell to face addressing OK.
 ***Unused points found in the mesh, number unused by faces: 38119 number unused by cells: 38119
  <<Writing 38119 unused points to set unusedPoints
  <<Found 1605 neighbouring cells with multiple inbetween faces.
    Upper triangular ordering OK.
  <<Writing 3222 unordered faces to set upperTriangularFace
    Face vertices OK.
    Number of regions: 1 (OK).

Checking patch topology for multiply connected surfaces...
                   Patch    Faces   Points                  Surface topology
    enclosure-enclosure:1     3930     7607      ok (closed singly connected)
                      fw   187002   369084  ok (non-closed singly connected)
                      rw   478397   948992  ok (non-closed singly connected)
                 chassis   837414  1645987  ok (non-closed singly connected)

Checking faceZone topology for multiply connected surfaces...
                FaceZone    Faces   Points                  Surface topology
    interior--enclosure-enclosure 64421568 44363855  multiply connected (shared edge)
  <<Writing 44360633 conflicting points to set nonManifoldPoints

Checking basic cellZone addressing...
                CellZone        Cells       Points       VolumeBoundingBox
    enclosure-enclosure     12900186     44364064   0.85091036 (-1.17151 -0.28899789 -0.42869264) (0.30197498 0.39209753 0.42869264)

Checking geometry...
    Overall domain bounding box (-1.17151 -0.28899789 -0.42869264) (0.30197498 0.39209753 0.42869264)
    Mesh has 3 geometric (non-empty/wedge) directions (1 1 1)
    Mesh has 3 solution (non-empty) directions (1 1 1)
    Boundary openness (-2.4131263e-18 4.3230956e-16 3.7196197e-17) OK.
    Max cell openness = 3.5348784e-16 OK.
    Max aspect ratio = 55.902331 OK.
    Minimum face area = 4.150095e-11. Maximum face area = 0.0024571784.  Face area magnitudes OK.
    Min volume = 1.8606933e-14. Max volume = 5.3705432e-05.  Total volume = 0.85091036.  Cell volumes OK.
    Mesh non-orthogonality Max: 81.900092 average: 8.0904361
   *Number of severely non-orthogonal (> 70 degrees) faces: 1118.
    Non-orthogonality check OK.
  <<Writing 1118 non-orthogonal faces to set nonOrthoFaces
    Face pyramids OK.
 ***Max skewness = 7.3641797, 222 highly skew faces detected which may impair the quality of the results
  <<Writing 222 skew faces to set skewFaces
    Coupled point location match (average 0) OK.

Failed 2 mesh checks.

End