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Old   October 1, 2007, 07:46
Default convergence, fluent
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rsi
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What should we do if 2 out of 10 CFD models do not converge? We need to compare CFD results amongst all 10 cases but 2 of them not converged. If we change under-relaxation factors for 2 of these, will our comparison be valid? What do people normally do when encounter this problem?
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Old   October 1, 2007, 14:21
Default Re: convergence, fluent
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bart weisser
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Can you give us details of your solution method?

*Transient, steady?

*Compressible, incompressible?

*Turbulent, laminar?

*Single component, multiple component (misible or not)?

*What is not converging (mass, momentum, or mass fraction)?

*Are residualrs normalized or not?

etc, etc ...

These would help determine where the problem likely lies.

BW.

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Old   October 1, 2007, 17:39
Default Re: convergence, fluent
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Pirooz Darabi
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Yes man,

Try be reducing the relaxation factors! Do not reduce them significantly though. And if did not work then you may have to refine your mesh or change your solution method.

Cheers Pirooz
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Old   October 4, 2007, 20:08
Default Re: convergence, fluent
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rsi
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steady state, incompressible, turbulent, single component, mass is not converging but when changed relaxn factor for pressure, the v-component is not converging.

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Old   October 5, 2007, 12:49
Default Re: convergence, fluent
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Bart Weisser
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On second thought ... it might be useful to look at your residual plots for the two quantities in question. I bet the residual is pretty low everywhere else except at some corner where it is exceedingly high. If that is the case I would suggest reviewing your boundary conditions or grid density in the offending vicinity. I hope that helps.

BW.
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