[Chander]

I am trying to ascertain the numerical accuracy of my simulations in CFX by following the procedure mentioned in the editorial policy of Journal of engineering.

My simulations are 3D turbulent flow . I take the overall pressure drop from inlet to outlet as the solution variable to calculate GCI and I use a representative mesh size for each mesh which I calculate as (total volume/total number of cells)^(1/3).

I have generated results for many meshes and tried to calculate GCI for 3 meshes at any time. I have ensured that the grid refinement ratios r21 and r32 are both above 1.3 for any of the mesh set that i consider.

However, I find that for the different mesh sets that i consider:
a)either the the parameter GCI_fine*(r21^p)/GCI_course is not close to one. This parameter should be close to one for the grids to be in asymptotic range.

b)when this parameter is indeed close to one for a set of meshes, (and GCI_fine is also is small..less than 2 percent), the observed order of accuracy p that I calculate comes out to be around 4 . Now I think it is incorrect and should be less than 2 (as the formal order of accuracy of CFX is 2...please correct me if I am wring). I have tried many fine and coarse meshes.

Is the way I am calculating GCI correct? Is the value of p>2 indeed correct?
For the results to be considered accurate what is the maximum acceptable value of GCI?