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iuaniu September 24, 2009 05:39

convergence criteria
 
Hi over there,

I am modeling a liquid-gas flow. The convergence criteria is RMS=1e-05.
All RMS go smooth (no oscillations) to the criteria AND BEYOND. All physical quantities of interest goes smooth as well. My question is: Why the simulation doesn't stop when the convergence is meet?

Thx,
Iuaniu

ghorrocks September 24, 2009 06:50

Have you also activated imbalances as a convergence criteria? Have you set a minimum number of iterations? There could be many reasons why it proceeds past your residuals criteria.

iuaniu September 24, 2009 08:56

Quote:

Originally Posted by ghorrocks (Post 230414)
Have you also activated imbalances as a convergence criteria? Have you set a minimum number of iterations? There could be many reasons why it proceeds past your residuals criteria.


The Conservation target is 0.01 (the default). I think I have found an answer in the documentation.

"To ensure the global balances are met, you may additionally apply a target imbalance for the conservation equations (i.e., a global balance criterion). In such a case, the solver will only stop before the maximum number of iterations if the residual criteria are met and global balances are also met. The value you specify is the fractional imbalance. The default value is 0.01 (i.e., 1%). "

Thank you for reply,
Iuaniu

ghorrocks September 24, 2009 19:20

There you have it. You activated imbalances as a convergence criteria and that had not been achieved, even though your residual had been achieved.


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