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Old   August 19, 2006, 21:45
Default Convergence Difficulties
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dear all

I am doing analysis on centrifugal blower. The analysis is not getting convergence for some changes in boundary conditions like mass flow at outlet.the maximum residual value for this case is 7e-04. but required one is 1E-04. i have checked converged results at different values of maximum residual value. the result is not much varing in between 8E-04 to 1E-04.

now my question is, can i take the results at residual of 8e-04 as final results?

if anybody know the answer please give reply.

thanks sarath
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Old   August 21, 2006, 06:22
Default Re: Convergence Difficulties
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Dear Sarath,

I had similar problems interms of convergence with my case (Axial Compressor). I was recommended, to specify Static Pressure as an outlet condition instead of the outlet massflow rate. This change worked in my case and I was able to effectively minimize convergence issues. Further refinements were made to the geometry and grid which gave me results, I was looking for !!!

If my memory has not let me down, it is highly recommened to have an RMS of 1E-06 (design condition) for any turbomachinary simmulation in CFX 10.0. Also if you search using the word "convergence" as a keyword within CFX 10.0 manual (mainly in CFX Pre and Solver PDFs), it should lead you to boundary setting and solver setting details for better convergence with accuracy.

I hope this piece of information helps you.....

Good luck.

Best regards, Arjun
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Old   August 21, 2006, 08:35
Default Re: Convergence Difficulties
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better to reach RMS at 1e-6 for convergence.
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