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about the fluent format mesh for openfoam

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Old   April 16, 2014, 14:55
Question about the fluent format mesh for openfoam
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Dear All,

My mesh was generated from ICEM and then output as the FLUENT V6 format. In the mesh file, actually, first the node information is list and then all the face information. The confusing for me now is the face information. For each triangular face, we have the following line for it:

Code:
 n0 n1 n2 cr cl
And in the fluent manual, it was explained that

Code:
This is an example of the triangular face format; the actual number of nodes depends on the element type. The ordering of the cell indices is important. The first cell, cr, is the cell on the right side of the face and cl is the cell on the left side.

Direction is determined by the right-hand rule. It states that, if you curl the fingers of your right hand in the order of the nodes, your thumb will point to the right side of the face. In 2D grids, the  k vector pointing outside the grid plane is used to determine the right-hand-side cell ( cr) from k*r .
The above information is from:
Code:
http://www.tchpc.tcd.ie/fluent/Unpacked_ISOs/TGrid__4.0_Documentation/tgrid4.0/help/html/ug/node380.htm
Since in openfoam, we always use the names of owner and neighbor cell for the cells that share one face. So in this cr is equivalent to neighbor cell while cl is equivalent to owner cell? Because in Jasak's Thesis, it was clearly stated that in Openfoam, the face area vectors (whose direction is also determined from right-hand rule) point from owner to neighbor cells.

The second question from the boundary face. In my case, I found that for all the physical boundary faces (like walls, inlet, ......, but excluding the inter-processor boundary faces), cr is non-zero whihle cl is zero. Since this is boundary face, so the non-zero cr must correspond to the interior cell what contains that face of interest. If I still assume face area vectors from owner (left) to neighbor (right) cells, this seems contradictory to my understanding: the normal of the boundary faces always point outwards, i.e. the interior cell is always owner.

Does anybody help me about this issue?

Thanks. OFFO
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Old   April 16, 2014, 15:20
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Hi OFFO,

Sorry, I came to this thread since you asked me, but I'm having a hard time to understand what exactly you want to know or do!?
  1. Are you trying to import a new format of a Fluent mesh to OpenFOAM?
  2. Or are you trying to understand how the mesh formats work on Fluent and on OpenFOAM?
Best regards,
Bruno
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Old   April 16, 2014, 15:22
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Thanks, Bruno.

I just would like to ask how the cr and cl in the fluent mesh file correspond to the owner and neighbor cells in openfoam. Because I always use fluent mesh format to convert it into openfoam format.

Thanks.
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Old   April 16, 2014, 15:44
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Hi OFFO,

The best I can do is to tell you to study the source code of the utility fluent3DMeshToFoam. The location for this code is given by this command:
Code:
echo $FOAM_UTILITIES/mesh/conversion/fluent3DMeshToFoam
If you prefer, you can also see it online here: https://github.com/OpenFOAM/OpenFOAM...3DMeshToFoam.L

Also, try having a look into the threads at this subforum: OpenFOAM Meshing Format & General Technical

Good luck! Best regards,
Bruno
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