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

Choosing the apt time step size for a transient run

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

Reply
 
LinkBack Thread Tools Display Modes
Old   March 31, 2012, 13:52
Default Choosing the apt time step size for a transient run
  #1
Senior Member
 
---------
Join Date: Oct 2010
Posts: 302
Rep Power: 8
saisanthoshm88 is on a distinguished road
I'm running a transient simulation and I see that some time steps are not converging with in the specified number of coefficient loops in CFX.

The number of coefficient loops specified is already 20 per time step, so I'd like to reduce the time step size now instead of increasing the number of coefficient loops per time step.

Is the time step size in any way related to the advection time in the .out file ?

If so, when I have the main domain and also some sub domains in the analysis so which advection time should be taken into consideration to decide the time step size?

Could some one please suggest me on this.
__________________
Best regards,
Santhosh.
saisanthoshm88 is offline   Reply With Quote

Old   March 31, 2012, 16:11
Default
  #2
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,646
Rep Power: 84
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
You should set the time step size by a sensitivity analysis. A good way to quickly converge on the correct time step is to use adaptive time steps, set to home in on 3-5 coeff loops per time step. This will quickly find the correct time step.
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
Effect of the time step size on the calculatino result norman_bates ANSYS 2 December 15, 2011 06:03
Full pipe 3D using icoFoam cyberbrain OpenFOAM 4 March 16, 2011 10:20
calculation diverge after continue to run zhajingjing OpenFOAM 0 April 28, 2010 04:35
Is there a way to write the time step size, time a may FLUENT 6 November 22, 2009 12:52
Modeling in micron scale using icoFoam m9819348 OpenFOAM Running, Solving & CFD 7 October 27, 2007 00:36


All times are GMT -4. The time now is 18:43.