[DanDoe]

Hi guys,

I was looking for a hex mesh of the Onera M6 airfoil and came across your tutorial + provided grid. I encounter the issue, though, that a few elements are distorted, i.e., the hexes/quads are effectively degenerated to prisms/triangles. When executing the example with `SU2_CFD` you actually get a corresponding warning:

```
------------------- Geometry Preprocessing ( Zone 0 ) -------------------
Three dimensional problem.
46417 grid points.
43008 volume elements.
3 surface markers.
2560 boundary elements in index 0 (Marker = FARFIELD).
1408 boundary elements in index 1 (Marker = WING).
2688 boundary elements in index 2 (Marker = SYMMETRY).
43008 hexahedra.
Setting point connectivity.
Renumbering points (Reverse Cuthill McKee Ordering).
Recomputing point connectivity.
Setting element connectivity.
Checking the numerical grid orientation.
>>> WARNING: 18 HEXAHEDRON, volume elements are distorted.
It was not possible to determine if their orientation is correct.
There has been a re-orientation of 4 QUADRILATERAL surface elements.
>>> WARNING: 1 QUADRILATERAL surface elements are distorted.
It was not possible to determine if their orientation is correct.
```

So my question is twofold:

1. Do you also provide the corresponding grid generation software, s.t. I can try improving the grid myself?
2. Is there a way to access the (possibly) improved grid? Based on `There has been a re-orientation of 4 QUADRILATERAL surface elements.` I have hope that the grid is improved at runtime. Using that grid might actually be good enough for me.

Best,
Daniel

[bigfootedrockmidget]

Hi,
I think the mesh originally came from here using the fortran program. Some of these programs output su2 files directly, not sure if that was the case for this one though:

https://turbmodels.larc.nasa.gov/one...erics_val.html


The re-orientation just means that we compute normals of faces, and all normals have to either point into the cell or out of the cell. If one of the normals is not like that, we flip the sign. So the mesh stays the same.

[DanDoe]

Thanks, I also played around with the mesh generation tools provided by NASA. Unfortunately, there are always some prisms in the mesh which make this not directly applicable for my code.

[DanDoe]

To shed some light on this I added two screenshots in the GitHub issue:

https://github.com/su2code/Tutorials/issues/59

[bigfootedrockmidget]

Well, In this case you could probably postprocess the mesh in an easy way and merge the remaining cells, that is if it is a matter of merging 2 connected prisms into 1 hexa cell.