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

Question about Multigrid in CFX

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

Reply
 
LinkBack Thread Tools Display Modes
Old   September 16, 2012, 07:13
Question Question about Multigrid in CFX
  #1
Senior Member
 
Anna Tian's Avatar
 
Meimei Wang
Join Date: Jul 2012
Posts: 494
Rep Power: 7
Anna Tian is on a distinguished road
Hi,

May I ask if there's an automatic way to implement the multigrid method in CFX?
__________________
Best regards,
Meimei
Anna Tian is offline   Reply With Quote

Old   September 16, 2012, 07:39
Default
  #2
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,926
Rep Power: 85
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
Um, yes - it is the default solver option. So if you have done a CFX simulation you have used a multigrid method.
ghorrocks is offline   Reply With Quote

Old   September 16, 2012, 13:25
Question
  #3
Senior Member
 
Anna Tian's Avatar
 
Meimei Wang
Join Date: Jul 2012
Posts: 494
Rep Power: 7
Anna Tian is on a distinguished road
Quote:
Originally Posted by ghorrocks View Post
Um, yes - it is the default solver option. So if you have done a CFX simulation you have used a multigrid method.
Thanks. But it seems not work very well. Because from my experience, if we do the multigrid manually, (Run the simulation for the coarse mesh firstly, then come to fine mesh with the result of coarse mesh simulation as the initial value file.), it converges much faster.

Does default multigrid method also work for multi-domain case in CFX?
__________________
Best regards,
Meimei
Anna Tian is offline   Reply With Quote

Old   September 16, 2012, 18:48
Default
  #4
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,926
Rep Power: 85
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
It is unlikely that any problem you are having with convergence is due to the linear solver, and even more unlikely that the manual control you describe will be any better.

If you are having convergence difficulties it is almost certainly due to some setup issue with your simulation. You should fix that problem rather than trying to tweak the linear solver.

The multigrid solver is the linear solver used by CFX for all simulations. So yes, it can handle multi-domain cases as well.
ghorrocks is offline   Reply With Quote

Old   September 16, 2012, 19:45
Default
  #5
Senior Member
 
Chris DeGroot
Join Date: Nov 2011
Location: Canada
Posts: 387
Rep Power: 6
cdegroot is on a distinguished road
To clarify, the linear solver in CFX uses algebraic multigrid which works on the coefficient matrix directly rather than a hierarchy of grids. As Glenn said it is the default solver and should work quite well in practically all cases. Manually transferring between grids is unlikely to be helpful.
cdegroot 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
question about governing equation in CFX using rotating/non rotating reference frame rystokes CFX 0 January 12, 2010 07:14
question about how to define diffusion coefficient in CFX rystokes CFX 0 December 12, 2009 06:32
Question about the shock wave in CFX software nucharin Main CFD Forum 1 January 25, 2005 09:26
simple question about ICEM CFX sleepinglily CFX 0 October 27, 2004 13:15
Question about meshing / solution scheme of CFX Coriolius CFX 8 August 1, 2004 18:39


All times are GMT -4. The time now is 10:27.