CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > FLUENT

Different Under Relaxation Factors

Register Blogs Community New Posts Updated Threads Search

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   November 4, 2004, 11:56
Default Different Under Relaxation Factors
  #1
Ertan
Guest
 
Posts: n/a
Hello everybody,

My question is, did anyone of you faced with different flow solutions if you keep everything same but only change Under Relaxation Factors?

thank you for contribution...
  Reply With Quote

Old   November 5, 2004, 04:47
Default Re: Different Under Relaxation Factors
  #2
Michael
Guest
 
Posts: n/a
In my opinion the solution of the problem shouldn't change. If you under-relax you should achieve the same results, however it will need more iterations.
  Reply With Quote

Old   November 5, 2004, 05:08
Default Re: Different Under Relaxation Factors
  #3
SAM
Guest
 
Posts: n/a
refine ur mesh . is ur mesh fine enough

did u make mesh dependence study

  Reply With Quote

Old   November 8, 2004, 15:13
Default Re: Different Under Relaxation Factors
  #4
Ertan
Guest
 
Posts: n/a
My mesh is 0.03inches tetrahedral. How can I make mesh dependence study?
  Reply With Quote

Old   November 9, 2004, 03:52
Default Re: Different Under Relaxation Factors
  #5
SAM
Guest
 
Posts: n/a
number ur number of noded

  Reply With Quote

Old   November 10, 2004, 13:21
Default Re: Different Under Relaxation Factors
  #6
gts
Guest
 
Posts: n/a
if you use a (very) small under relaxation factor you will have no changes in the solution and you can obtain the steady state. You shoul also try to take lower residuals
  Reply With Quote

Old   November 10, 2004, 19:38
Default Re: Different Under Relaxation Factors
  #7
ap
Guest
 
Posts: n/a
If you use too small under-relaxation factors you risk to obtain false convergence.

This means that in unsteady calculations, you have a sort of lag between the real flow conditions at a time and the predicted flow condition.

In steady calculations, false convergence means you don't reach the solution.

Under relaxation factors have to be reduced with care, keeping in mind that you just have to reduce them in order to obtain a stable solution.

Hi

ap
  Reply With Quote

Old   November 11, 2004, 05:07
Default Re: Different Under Relaxation Factors
  #8
gts
Guest
 
Posts: n/a
Of course the steady state obtained using a small ur could be a "wrong steady state"
  Reply With Quote

Reply


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
Relaxation Factors for Transient solvers philippose OpenFOAM Running, Solving & CFD 19 March 20, 2014 05:39
Purpose of relaxation factors Mohsin FLUENT 5 April 30, 2010 12:57
relaxation factors and time accuracy Mike Main CFD Forum 7 May 21, 2005 13:41
Relaxation Factors Tim Phoenics 3 June 30, 2004 03:03
relaxation factors adjust zhujianguo Phoenics 1 July 15, 2003 12:11


All times are GMT -4. The time now is 20:34.