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CFX Solver Control, Max iteration

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Old   May 15, 2012, 11:43
Default CFX Solver Control, Max iteration
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Adil Syyed
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I am doing a steady state analysis.
I have given maximum iterations in solution control to be 10000 with physical timescale of 5 sec.
The solver gives me result in 55 iterations, and does not go for the whole 10000 iterations.
Why?
And before this, in the very same analysis, I just specified maximum iterations to be 1000 with 2 sec physical timescale, and the solver go up to complete 1000 iterations.
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Old   May 15, 2012, 12:10
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Erik
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Did you reach your convergence criteria? That would also stop the run.
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Old   May 15, 2012, 13:06
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Kyriakos Vafiadis
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Check what's the convergence criteria: RMS or MAX Residual Target. Also, check the way you define your Timescale.
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Old   May 15, 2012, 13:32
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Quote:
Originally Posted by k.vafiadis View Post
Check what's the convergence criteria: RMS or MAX Residual Target. Also, check the way you define your Timescale.
RMS, RMS target 0.0001

And what do you mean by he way I define your Timescale?
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Old   May 16, 2012, 04:32
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A reasonable physical time scale value selection is important for good and faster convergence.
So for time scale 2sec and RMS target 10^-4 the solver needed 10000 (or more?) iterations to converge.
But with time scale 5sec and RMS 10^-4 the solver converged (converged to your RMS target) with only 55 iterations.
According to CFX Solver Modeling Guide (Chapter 14), physical time scales that are too large are characterized by bouncy convergence or results that do not converge. Time scales that are too small are characterized by very slow, steady convergence.
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