[Annemiek]

Hello,

I am trying to figure out if there is any logical structure in how Pointwise outputs the location of the points for a SU2 grid.

I made a simple two-block structured mesh consisting of 2 cubes attached to each other, similar to the picture below.

http://www.mathworks.com/matlabcentr...woCubes_01.png

On each connector I specified 3 points, giving a total of 45 points. When looking at the SU2 mesh file generated by Pointwise, these points seem to have a random index order, the index is the last column in the text below.

NPOIN= 45
0.0 3.0 1.5 0
0.0 3.0 0.0 1
0.0 3.0 3.0 2
1.50 3.0 3.0 3
...
...
...

Also the indexing of the hexahedrons change from one block to the other.

Does anyone know how the indexing is done?

Thanks,

Annemiek

[tcarrigan]

Annemiek,

The SU2 grid file format is unstructured, despite exporting structured blocks. A great place to start is their documentation here, https://github.com/su2code/SU2/wiki/Mesh-File

[Annemiek]

HI,

Thanks, I found this page before indeed. Maybe I posed my question wrong, but the ordering of the points in the 2D image on that page looks like it has some structure. The points are indexed from left bottom to right top.

I was wondering if there is something similar for the 3D mesh, so if there is some structure in the indexing of the points.

Annemiek

[dgarlisch]

Annemiek,

There is a non-trivial logic to the ordering of the exported points. However, that ordering depends on several factors that are not accessible outside the Pointwise code. Even more importantly, the ordering is not guaranteed to stay the same from one Pointwise release to the next.

In general, ordering depends on the number and types (str or uns) of the exported blocks. Point ordering is different for structured and unstructured blocks.

If you intend on developing some code or algorithm that depends on the point ordering, it will not be reliable. If the point ordering changes in the future, your code will probably break.

If you can provide more details on why you need to know the ordering, I may be able to offer other solutions.

[Annemiek]

Hi,

Thanks! That's what I wanted to know

I want to make some mapping from the unstructured mesh output back to the structured such that I can do post processing in Matlab. Some sort of i,j,k ordering of the points, so that I can for example look at the solution up to a certain i-location or j-location on a certain interval.

Annemiek

[dgarlisch]

I was afraid you were going to say that!

Unfortunately, there is no way that I know of to do that other than brute force analysis. And for large grids, that can be very slow.

However, IF your post processing can deal with the blocks being exported one at a time, you may be able to take advantage of one quirk.

When a single structured block is exported, the vertices are exported in the blocks IJK order! However, this is not true if the block is self-connected (O-H topology, etc) or if the block has any poles.

I must emphasize that this behavior could change in the future (I don't expect that to happen any time soon).

I hope this helps.

Originally Posted by Annemiek

I want to make some mapping from the unstructured mesh output back to the structured such that I can do post processing in Matlab. Some sort of i,j,k ordering of the points, so that I can for example look at the solution up to a certain i-location or j-location on a certain interval.
Annemiek