Cell area issue
I have a wierd issue with FLUENT 12. In my 2D mesh I have a semi-circle shaped edge, which I have meshed with a constant spacing.
But when I look at the Face Area Magnitude (either through XY-plot, or through exporting through a udf using F_AREA(A,f,t); & area = NV_MAG(A); ) it varies along the edge. :confused:
Surely as the mesh has a constant spacing, the area of the each cells face should be the same...if I do the same on a straight edge, the reported area is constant.
I can't remember off the top of my head but I think the face area magnitude calculation in FLUENT is vector direction dependent. I notice that the area value in the graph is biggest for the cells that are parallel with the yellow line on the bottow of the domain and drops to zero for the cells that are perpendicular to this line. My assumption is that the vector direction it is using is normal to the yellow line. See if you can change this direction, but ultimately you will need to use a different calculation of area I think.
OK. So I queried this with ANSYS support and this was the response. It is important to note that in my description here I forgot to say that it is axisymetric about the yellow line
Thinking about this, I understand it a bit more, so will clarify for future reference.
In the 2D case the area of the cell is calculated based on the length of the edge of the cell times by the distance in the third (non-existent) direction. As for the values of C_D and C_L in 2D, FLUENT uses a unit vector in the third direction and so the area is calculated based on #cell_edge_length# x #unit_in_z_direction#. In the axi-symmetric case the 3D version of the cell is actually a wedge shape, which is narrower the closer you get to the axis, hence making the cell area dependent on distance away from the axis.
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