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Old   February 19, 2015, 12:34
Default CGNS Boundary conditions using SU2
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I have a question about implementing boundary conditions on my CGNS mesh while using SU2.

My mesh is consists of a simple car within a rectangular control volume.

The surfaces of the car are marked as "simplecar", which is being recognized while running SU2.

The problem I encounter is with the other Markers; I don't understand how I can assign the appropriate boundary conditions towards these markers.

These control volume markers are:
- velocity-inlet
- pressure-outlet
- side-left
- side-right
- top
- road

Within the SU2 documentation I found this:

It is important to note that SU2 will not use any specific boundary conditions that are embedded within the CGNS mesh. However, it will use the names given to each boundary as the marker tags. These marker tags are used to set the boundary conditions in the configuration file. Therefore, it is recommended that the user give names to each boundary in their mesh generation package before exporting to CGNS. If you do not know the number of markers or their tags within a CGNS file, you can simply attempt a simulation in SU2_CFD (leaving out the boundary information in the configuration file at first), and during the preprocessing stage, SU2 will read and print the names of all boundary markers to the console along with other grid information before throwing an error due to incomplete boundary definitions. The user can then incorporate these marker tags into the configuration file with the appropriate boundary conditions.

My question is thus the last sentence. How do I do this within the config file?

I figured it would be, for e.g. the inlet marker

MARKER_INLET= ( velocity-inlet, 1.225, 0.10, 0, 1, 0 )
( marker, density, velocity (in Mach?), unit vector in x, unit vector in y, unit vector in z )

SU2 complains as follows:
Loading CGNS data into SU2 data structures...
Three dimensional problem.
155452 interior elements.
131752 tetrahedra.
23700 prisms.
38686 points.
8 surface markers.
4279 boundary elements in index 0 (Marker = SIMPLECAR).
342 boundary elements in index 1 (Marker = VELOCITY-INLET).
The configuration file doesn't have any definition for marker VELOCITY-INLET!!

Any help on how to implement boundary conditions is much appreciated!

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Old   February 20, 2015, 02:04
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Francisco Palacios
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Hi Denzell,

Thanks for using SU2, the capitalization is important, could you please try with

MARKER_INLET= ( VELOCITY-INLET, 1.225, 0.10, 0, 1, 0 ).

The velocity should be in m/s or in/s

Best Regards,

Francisco Palacios
SU2 lead developer
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Old   February 20, 2015, 15:33
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Dear Mr. Palacios,

Thank you for your quick reply, that helped to resolve the problem.

The next problem I face is the following.

The CGNS mesh consists of a fluid volume "AIR" which is a rectangle with a boolean subtract operation of the vehicle geometry.

Because this volume has a name "AIR", I think SU2 interprets this volume such that it requires extra identification of what this volume is. I think this because of the following error:

The configuration file doesn't have any definition for marker AIR_1_1!!

Where the subscript _1_1 comes from is unclear to me by the way.

Do you maybe have a suggestion how I can indicate that AIR (_1_1) can be treated as a fluid?

Thanks again and have a nice weekend,


PS: For the sake of completeness I have added the CGNS file and current config file within this folder if this helps:
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