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-   -   Divergence in amg solver while using second order scheme (http://www.cfd-online.com/Forums/fluent/108850-divergence-amg-solver-while-using-second-order-scheme.html)

raj November 2, 2012 13:51

Divergence in amg solver while using second order scheme
 
Hi all
Iam doing a transient combustion analysis with partially premixed model and compressible case. I am using k-e realisable turbulence model. While running the case with all methods set to first order i got good convergence of results. However when i changed to second order schemes i get the amg solver divergence . Kindly suggest me what could be the problem

vicarious November 2, 2012 14:34

Second order Schemes got less relaxation to the high gradients because the adjacent cells involved are more( j+2,J-2), thus the high gradients of parameters could result in a bad behavior. Try to decrease your RFs and check the Green-Gause node based in solver panel.

Regards.

raj November 3, 2012 00:39

Hi Thanks for the reply
I have reduced the relaxation factors and the solver is running. But i would like to ask one thing whether by reducinf the RF's does it alter the final results?

cfd seeker November 3, 2012 02:10

Quote:

Originally Posted by raj (Post 389995)
Hi Thanks for the reply
I have reduced the relaxation factors and the solver is running. But i would like to ask one thing whether by reducinf the RF's does it alter the final results?

No your final solution will remain unaltered however your convergence time will be more with the reduced values of RF's


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