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TWaung September 22, 2009 17:52

Need Help Understanding RMS residual calculation
 
Hello,

I have 2 questions regarding the calculation of residuals.

Here is a description of my problem:
I have an air intake simulation (subsonic, SST turb model) that has fairly small regions of flow separation.

The RMS residuals for the Momentum variables are around 5e-5 to 1e-4, while the Max residuals are up around 1e-2.

When I look at the results in Post and create an isovolume of u-momentum residuals above(inclusive) 1e-5, the volumes that meet this condition are very small and located in the regions of separation. Even when I set the isovolume to show regions above 1e-6, the amount of volume displayed is quite small relative to the size of my entire domain.

I would have expected the RMS residuals to be lower based on the results seen in Post.

Question 1: When the raw residuals are normalized, is cell volume taken into account? The help file indicates that the residuals are normalized with respect to the control volume coefficient and a representative value of the variable being normalized. Do either of these account for cell volume?

Question 2: Is it possible to have a relatively small volume of high residuals skew the RMS residual values to be large? Or am I not interpreting the results correctly?

Thanks for any help anyone can provide.

Tim

ghorrocks September 22, 2009 18:21

Q1 - Yes, cell volume is taken into account.
Q2 - Yes.


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