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Red1 July 13, 2012 11:07

Neighboring Cells on FLUENT
Hello everyone, can anyone help me with a specific problem. I try to compare a quantity (such as tempreture) of a cell of a quadratic mesh with neighboring cells (8 cells for 2D case ans 26 for 3D the one). There's someone there to help me? Thank you in advance!

flotus1 July 14, 2012 03:07

Until now, I haven't found a straightforward solution to this problem.
I came to believe that there is no way of reading a neighboring cell directly.

In your case, there could be a workaround since you have very few cells and you know the cell extent.

It goes like this:

loop over all the cells and read the value you want to compare (e.g. temperature).
Store the position of this cell.
Now WITHIN this cell loop, loop over all the cells again and compare the position of the cell to the position you just stored.
If for example the position in X is one cell extent away and the position in Y is the same, that is a neighboring cell. Now you can read the Temperature again and compare it to the stored value.

I already did something similar, it works.
Keep in mind that the computational effort is proportional to the number of cells^2. So compiling the UDF instead of interpreting it is recommended to speed it up.

flotus1 July 14, 2012 04:47

Another possibility with a structured uniform mesh would be to store the value in an array T[x][y][z] in a first loop over all cells.

In a second loop, you can compare the values.

This would reduce the computational effort to 2*(Number of cells). What a speedup:D

By the way: if you should ever stumble upon a simple solution for this problem, please let me know.

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