CFX-Post Bug : Averaging Function

turbo · January 19, 2016, 13:00

In the CFX-Post, the averaging function should not be trusted in any surface cut because of malfunction at some locations where the mesh is not well aligned with the cut direction.

Through a tiresome communication with Ansys support, they accepted my claim to inform that the bug has recently been fixed in R17.0 which is not released yet.

In the inlet-to-outlet chart of a compressor stage, the mass-averaged absolute total temperature fluctuates downstream of the rotor, as shown in the attached file, which should be flat in physics. The small change of total temperature will give you a bigger change of compressor or rotor efficiency calculation.

Please note that do not try to find any averaged value where the mesh lines are not well aligned with your cut. The value is wrong for now !

ghorrocks · January 19, 2016, 17:18

Does this apply to all the averaging functions - ave, massFlowAve, volumeAve, rmsAve, areaAve?

turbo · January 19, 2016, 20:54

Hi ghorrocks,
I found the bug from both mass-averaging and area-averaging, but guess all the others you asked would be affected by the wrong interpolation between the cut face and skewed mesh faces. The more mesh lines are deviating from the cut, the more inaccurate value you will get.

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January 19, 2016, 17:18		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,701 Rep Power: 143	Does this apply to all the averaging functions - ave, massFlowAve, volumeAve, rmsAve, areaAve?

January 19, 2016, 20:54		#3
turbo Senior Member Join Date: Jun 2009 Posts: 174 Rep Power: 16	Hi ghorrocks, I found the bug from both mass-averaging and area-averaging, but guess all the others you asked would be affected by the wrong interpolation between the cut face and skewed mesh faces. The more mesh lines are deviating from the cut, the more inaccurate value you will get.