[sylvain91]

I am trying to convert a channel mesh from star to Open Foam. I used starToFoam and it apparently worked. However visualising the mesh with paraview I noticed that some cells were missing in the middle part of the channel and I don't know why. I have run checkMesh and several error messages appeared. It is apparently due to high aspect ratio of the cells I used but it is the case of my model and I had no problem running LES with Star using the same mesh.

I don't know if I missed some precautions using starToFoam, if someone could give me a hint of what's happening I wrote one example of each kind of error message. Thanks in advance for your help


CheckMesh result:

Create polyMesh for time = constant

Time = constant
Boundary definition OK.

Number of points: 266175
edges: 786110
faces: 773888
internal faces: 749824
cells: 253952
boundary patches: 6
point zones: 0
face zones: 0
cell zones: 0

Checking topology and geometry ...
Point usage check OK.

Upper triangular ordering OK.

Topological cell zip-up check OK.

Face vertices OK.

Face-face connectivity OK.

Basic topo ok ...

Checking patch topology for multiply connected surfaces ...

Patch Faces Points Surface
CYCL1 3968 4095 ok (not multiply connected)
CYCL2 3968 4095 ok (not multiply connected)
CYCL3 3968 4095 ok (not multiply connected)
CYCL4 3968 4095 ok (not multiply connected)
WALL5 4096 4225 ok (not multiply connected)
WALL6 4096 4225 ok (not multiply connected)


High aspect ratio for cell 129001: 3.26251e+196

Zero or negative face area detected for internal face 385902 between cells 129972 and 129973. Face area magnitude = 0

FOAM Warning :
From function primitiveMesh::checkFaceDotProduct(const bool report, labelHashSet* setPtr) const
in file meshes/primitiveMesh/primitiveMeshCheck.C at line 534
Severe non-orthogonality detected for face 354814 between cells 119512 and 119576: Angle = 90 deg.

Severe skewness for face 359692 skewness = 3.78579e+300

Zero size or very small edge size detected for edge 413917 vertices (139390 143615). Length = 0

--> FOAM Warning :
From function checkEdges(const primitiveMesh& mesh, const bool report,const scalar tol, labelHashSet* setPtr
in file checkEdges.C at line 96
16900 small edges found

Writing 21125 points on short edges to set shortEdges

All angles in faces are convex or less than 10 degrees concave.

Face flatness (1 = flat, 0 = butterfly) : average = 1 min = 1
All faces are flat in that the ratio between projected and actual area is > 0.8

Geometry check done.

Number of cells by type:
hexahedra: 253952
prisms: 0
wedges: 0
pyramids: 0
tet wedges: 0
tetrahedra: 0
polyhedra: 0
Number of regions: 1 (OK).
Failed 4 mesh checks.

Time = 0
No mesh.

End

[hjasak]

Have a look at your mesh very very carefully. Star is using tolerance-based mesh manipulation, which causes errors when the cells are thin and the solver then keeps quiet about it. Anyway, if the mesh is wrong, you will not get the correct result.

The second possibility is that the points are written out from Prostar with insufficient accuracy. Specifically, check the location of points 139390 and 143615: OpenFOAM says they are on top of each other - this would be a typical mesh generation error with Prostar.

Hrv