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

under relaxation for natural convection

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

Reply
 
LinkBack Thread Tools Display Modes
Old   November 18, 2008, 18:37
Default under relaxation for natural convection
  #1
Jimmy
Guest
 
Posts: n/a
For natural convection, what are the best practices to set under relaxation parameters? Thanks.
  Reply With Quote

Old   November 19, 2008, 07:33
Default Re: under relaxation for natural convection
  #2
Wiebe
Guest
 
Posts: n/a
Hello Jimmy,

In my experience natural convection and mixed convection problems can be hard to converge. Tricks that you can try are:

- reduce the relaxation parameters. (generally never to less than about 20% of the standard setting)

- get a first order upwind solution before switching to second order accuracy.

- Use time steps instead of a steady state solution to get an approximate answer, then possibly return to steady state.

Also be aware of the fact that standard wall functions are not developed to be used in natural convection cases. the options you have here depend on which program you are using. (in case of enhanced wall treatment, check your grid!)

Regards, Wiebe.
  Reply With Quote

Old   November 19, 2008, 20:30
Default thanks much *NM*
  #3
Jimmy
Guest
 
Posts: n/a
  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
natural convection problem with radiation jorien CFX 0 October 14, 2011 09:26
Purpose of relaxation factors Mohsin FLUENT 5 April 30, 2010 11:57
Relaxation and convergence sammi Phoenics 0 March 20, 2008 04:32
Coupled vs Seg - Natural vs. Forced Convection Alex CD-adapco 5 December 12, 2007 05:58
Question on adjusting relaxation factor CFD Rookie Main CFD Forum 3 January 26, 2004 15:37


All times are GMT -4. The time now is 08:10.