SU2 not exporting BCs patches when CGNS is selected as output

[LorenzoFabris]

Describe the bug
After the OUTPUT_FILE = CGNS option was added I decided to use it to export my mesh from SU2 to CGNS after my CFD calculation converged.
SU2 correctly generates the mesh file in CGNS format. However, boundary patches are not present and the mesh consists of a huge block.

MESH GENERATION

AFTER CONVERSION FROM .su2 to .cgns

Thank you in advance for your help.

Bug report checklist

• [ ✓] Consulting the build instructions (https://su2code.github.io/docs_v7/Build-SU2-Linux-MacOS/).
• [ ✓] Looking for similar problems on GitHub or CFD-Online (https://www.cfd-online.com/Forums/su2/).
• [✓ ] Updating to the newest version of SU2 (either develop, master, or the pre-built executables https://su2code.github.io/download.html).

Desktop (please complete the following information):

• OS: [e.g., Ubuntu 20.04]
• C++ compiler and version: GCC 11.2
• MPI implementation and version: OpenMPI 5.0.6
• SU2 Version: 8.1.0 Harrier

[bigfooted]

Is this boundary information written if you export to SURFACE_CGNS?

[LorenzoFabris]

Is this boundary information written if you export to SURFACE_CGNS?

Hi Nijso,

SURFACE_CGNS only outputs the surface of the blade in this case

[bigfooted]

But you could write all surfaces to SURFACE_CGNS, and the information that is written to SURFACE_CGNS is the information that is missing in the regular CGNS? SU2 writes surface and volume information independently, so then we 'only' have to combine this information into one single file.
Does CGNS keep track of how the surfaces are connected to the interior, i.e. does it share the points? If not, then it might be easy to combine this information into a single file

[LorenzoFabris]

But you could write all surfaces to SURFACE_CGNS, and the information that is written to SURFACE_CGNS is the information that is missing in the regular CGNS? SU2 writes surface and volume information independently, so then we 'only' have to combine this information into one single file. Does CGNS keep track of how the surfaces are connected to the interior, i.e. does it share the points? If not, then it might be easy to combine this information into a single file

For some reason, after the merging, the CGNS does not "conserve"the BCs patches, making this a pain during post processing.
Generally, yes: X,Y,Z points are shared, I checked via terminal.
If you have any suggestion, I'm all ears :)

[7akashs]

Hi Lorenzo & Nijso,
Thanks for opening this issue.
I am also trying to do sort of same thing. I will explain with an example: Lets say I have a stator zone with Hub, shroud, blade, periodic boundaries, inlet and outlet, the SU2 exports it into CGNS format separately as well as an internal mesh with them. And I tried merging/combining them with python code, it did merge them into complete entity (stator) but somehow it misses the information of the boundary condition, possibly because the Su2 output of CGNS contains it as a zone without any boundary condition. Do you have any suggestions, how we can over come this, how the boundary information can be added or carried with the CGNS file?
Let me know if you need any other information.