CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > Siemens > STAR-CCM+

Conjugate-Gradient solver did not converge!

Register Blogs Members List Search Today's Posts Mark Forums Read

Like Tree9Likes
  • 9 Post By ignat

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   January 26, 2014, 21:40
Question Conjugate-Gradient solver did not converge!
  #1
New Member
 
sazrul
Join Date: Jul 2013
Location: Kuala Lumpur
Posts: 4
Rep Power: 12
sazrul is on a distinguished road
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.
sazrul is offline   Reply With Quote

Old   January 29, 2014, 09:19
Default
  #2
New Member
 
Alexey
Join Date: May 2009
Location: St.Petersburg, Russia
Posts: 23
Rep Power: 16
ignat is on a distinguished road
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
LuckyTran, Venk, SB123 and 6 others like this.
ignat is offline   Reply With Quote

Old   April 18, 2016, 17:43
Default
  #3
New Member
 
sulaiman
Join Date: Feb 2016
Posts: 18
Rep Power: 10
sms1424 is on a distinguished road
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!
sms1424 is offline   Reply With Quote

Old   April 19, 2016, 14:36
Default
  #4
New Member
 
Alexey
Join Date: May 2009
Location: St.Petersburg, Russia
Posts: 23
Rep Power: 16
ignat is on a distinguished road
Quote:
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!
ignat is offline   Reply With Quote

Old   April 19, 2016, 15:02
Default
  #5
New Member
 
sulaiman
Join Date: Feb 2016
Posts: 18
Rep Power: 10
sms1424 is on a distinguished road
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!
sms1424 is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Creating New Solver: For particle-laden compressible jets sankarv OpenFOAM Running, Solving & CFD 17 December 3, 2014 20:41
Creating New Solver: For particle-laden compressible jets sankarv OpenFOAM 0 April 4, 2010 19:06
Can segregated solver be used for compressible flow? Steven-GY ANSYS 0 May 14, 2009 11:37
compressible two phase flow in CFX4.4 youngan CFX 0 July 2, 2003 00:32
Poisson eq and conjugate gradient method Gary Dantinne Main CFD Forum 2 March 19, 1999 01:24


All times are GMT -4. The time now is 17:15.