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Old   February 10, 2012, 06:10
Default Translational Periodicity
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Hi folks,

I am new to the CFD world and have a question regarding the translational periodicity in Ansys CFX and the way it is displayed in CFX-Pre. I hope my upcoming question is not answered in this forum yet, otherwise I apologize for not finding it.

At the moment I am doing a Grid Convergence Index-study where I want to identify the robustness of my grid. Therefore I created a fine and coarse derivative of my baseline grid. Both the coarse and baseline grid show a nice convergence in CFX-Solve but the residuals of the fine grid oscillate severely after 200 Iterations.
I assume the high resolution of the 'fine grid' takes transient effects into account which is the reason for the described convergence problems. Nevertheless I noticed something strange while looking at the translational periodicity. If you compare the pictures of the fine and baseline grid in CFX-Pre you recognize that the arrows that display the periodicity are not symmetric in the fine grid version! Is this something to worry about? Does anyone know the reason for this inaccurate display?

I attach a couple of pictures to this thread that should illustrate what I am talking about. Thank you very much in advance!

Best Regards,
Clavigo
Attached Images
File Type: jpg 20120210_GCI_fine.jpg (22.0 KB, 16 views)
File Type: jpg 20120209_GCI_baseline_solve.jpg (38.7 KB, 9 views)
File Type: jpg 20120209_GCI_fine_solve.jpg (39.0 KB, 9 views)
File Type: jpg 20120209_GCI_basline.jpg (22.7 KB, 14 views)
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Old   February 10, 2012, 12:01
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Quote:
Nevertheless I noticed something strange while looking at the translational periodicity.
Just refining the mesh does not disturb the periodicity. This may be due to graphics display issues.

You are getting good convergence with both meshes.
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