CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > CFX

convergence criteria

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

Reply
 
LinkBack Thread Tools Display Modes
Old   September 24, 2009, 05:39
Exclamation convergence criteria
  #1
New Member
 
Iuaniu
Join Date: Sep 2009
Posts: 4
Rep Power: 7
iuaniu is on a distinguished road
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
iuaniu is offline   Reply With Quote

Old   September 24, 2009, 06:50
Default
  #2
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,278
Rep Power: 82
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
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.
ghorrocks is offline   Reply With Quote

Old   September 24, 2009, 08:56
Default
  #3
New Member
 
Iuaniu
Join Date: Sep 2009
Posts: 4
Rep Power: 7
iuaniu is on a distinguished road
Quote:
Originally Posted by ghorrocks View Post
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
iuaniu is offline   Reply With Quote

Old   September 24, 2009, 19:20
Default
  #4
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,278
Rep Power: 82
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
There you have it. You activated imbalances as a convergence criteria and that had not been achieved, even though your residual had been achieved.
ghorrocks is offline   Reply With Quote

Reply

Thread Tools
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 On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Convergence criteria PrandtlGlawert FLUENT 1 August 13, 2009 18:06
Convergence Criteria edwin FLUENT 1 February 14, 2008 20:24
Convergence criteria Gaurav CD-adapco 0 February 3, 2006 05:53
Convergence criteria Sileno Phoenics 1 December 6, 2005 08:25
CAVITATION (convergence criteria & discretization) ROOZBEH FLUENT 1 October 6, 2003 09:32


All times are GMT -4. The time now is 18:10.