Hi, everybody,

I draw a square in Gambit and copy it to get an another surfce parallel to the original square, then mesh them. In Fluent, using "cell_t c" in a UDF, I got sort orders of cells in two squres. I found the sort order of cells in the original squres is from bottom to top, but in the its paraller surface the order is from top to bottom. In the other word, the cell numbered "1" in original surface lies in its left-top corner, however the cell numbered "1" in the paraller surface is in its left-bottom corner. My question are (1)why are their sort orders different? (2) how does the FLUENT determine the sort order of mesh cells in a surface or a volume?

Thank you very much! braket

By the way, how to determine which is the first cell in a thread? In a squre, there are four corners. which corner a cell lies is the first cells in the squre thread? thank you very much! braket

I dont know a way to determin the cell order in a grid. Cells are stored in a sprase matrix and to reduce memory consumption some cells are shifted to positions where usually zero elements are stored. You can even force this with grid->reorder. Here is a small expamle to illustrade the process:

Original 5x5 matrix (A-E are stored elements)

A0000
0B000
00C00
000D0
0000E

3x3 matrix after reordering

BA0
0C0
0ED

As you can see the new cell oder is screwed up and there is no shure fire way to determin the cell order for large grids.

RoM