# Can this solution be regarded as converged?

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

April 1, 2011, 06:15
Can this solution be regarded as converged?
#1
Senior Member

Join Date: Oct 2010
Location: Zurich
Posts: 176
Rep Power: 8
I am simulating turbulent flow with conjugate heat transfer and I have specified the following convergence criteria:

RMS residual for mass, momentum and energy equations as 1E-6. AND Conservation target as 0.001%

Now I am facing trouble with getting the required convergence. Please refer the attached residual plots. The residual for mass drops below 1e-6. But residual for momentum stabilizes around 1e-5 and that for energy around 5e-6. Regarding the conservation target, the maximum domain imbalance is around 0.006% for H-energy for the fluid domain.

Can this solution be regarded as converged. The question may sound stupid as clearly the specified convergence criteria has not been met. But I had no theoretical basis for specifying 1e-6 as the convergence criteria in the first place. Had i specified 1e-5 as the convergence criteria for equations with no criteria for conservation target, I would not have even observed this behavior.
Attached Images
 Momentum_and_mass_residuals.png (14.1 KB, 36 views) Heat_Transfer_residuals.png (10.7 KB, 32 views)

 April 1, 2011, 07:10 #2 Senior Member   Stuart Join Date: Jul 2009 Location: Portsmouth, England Posts: 506 Rep Power: 15 It might a good idea to show the same plots again but when it is solved an a finer mesh, apply a gloabl scaling factor to reduce element size, to see if the convergence changes.

 April 1, 2011, 09:24 #3 Senior Member   Join Date: Apr 2009 Posts: 532 Rep Power: 14 Looks like good convergence to me! Check the T-Energy imbalance in the solid just to be safe, but I expect it's fine.

 April 3, 2011, 06:42 #4 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 13,535 Rep Power: 104 This question has been asked hundreds of times.... So I wrote an FAQ: http://www.cfd-online.com/Wiki/Ansys...gence_criteria

 Thread Tools Display Modes Linear Mode

 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 OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post gueynard a. Main CFD Forum 19 June 27, 2014 21:22 makaveli_lcf OpenFOAM Running, Solving & CFD 3 September 11, 2013 12:44 Louis Le Grange OpenFOAM 0 October 5, 2009 10:53 julie FLUENT 4 November 14, 2005 09:35 Abhijit Tilak Main CFD Forum 6 February 5, 1999 02:16

All times are GMT -4. The time now is 03:55.