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Conjugate-Gradient solver did not converge!

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Old   January 26, 2014, 21:40
Question Conjugate-Gradient solver did not converge!
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sazrul
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Hi experts,

Currently I am running an Under hood Thermal Management analysis using Star-ccm+ v8.06.005. However, I am facing this error; 'Conjugate-Gradient solver did not converge' while I am trying to run the solution.

Can anyone tell me what does this error means? What should I do to fix it?

Your kind help is highly appreciated .

Regards,
Sazrul
Kuala Lumpur.
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Old   January 29, 2014, 09:19
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Alexey
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Quote:
Originally Posted by sazrul View Post
Hi experts,

Currently I am running an Under hood Thermal Management analysis using Star-ccm+ v8.06.005. However, I am facing this error; 'Conjugate-Gradient solver did not converge' while I am trying to run the solution.

Can anyone tell me what does this error means? What should I do to fix it?

Your kind help is highly appreciated .

Regards,
Sazrul
Kuala Lumpur.
It is not serious problem. CG method is used for acceleration pressure solver and this message means only that your task is calculated without acceleration.

You may switch off CG and this message the following way.
Select:

Solver->Segregated Flow->Pressure->AMG Linear Solver->Acceleration method->None
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Old   April 18, 2016, 16:43
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Quote:
Originally Posted by ignat View Post
It is not serious problem. CG method is used for acceleration pressure solver and this message means only that your task is calculated without acceleration.

You may switch off CG and this message the following way.
Select:

Solver->Segregated Flow->Pressure->AMG Linear Solver->Acceleration method->None
I am simulating turbulent flow inside a duct, and faced the same issue.

If I ignore the acceleration, I believe that will affect my simulation, Am I right?
Is there a way to fix this issue and get convergence w/o ignoring acceleration?

Thanks!
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Old   April 19, 2016, 13:36
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Alexey
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Originally Posted by sms1424 View Post
I am simulating turbulent flow inside a duct, and faced the same issue.

If I ignore the acceleration, I believe that will affect my simulation, Am I right?
Is there a way to fix this issue and get convergence w/o ignoring acceleration?

Thanks!
If you ignore the acceleration then that will affect on execution time only. Not solution.
If you don't want to ignore the acceleration then try to make experiments, for example decreas Under-relaxation factor.
Solver->Segregated Flow ->Velocity->Under-relaxation factor

and

Solver->Segregated Flow ->Pressure->Under-relaxation factor

Good luck!
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Old   April 19, 2016, 14:02
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Quote:
Originally Posted by ignat View Post
If you ignore the acceleration then that will affect on execution time only. Not solution.
If you don't want to ignore the acceleration then try to make experiments, for example decreas Under-relaxation factor.
Solver->Segregated Flow ->Velocity->Under-relaxation factor

and

Solver->Segregated Flow ->Pressure->Under-relaxation factor

Good luck!
Thank you so much!
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