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

Transient run taking too long time

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

Reply
 
LinkBack Thread Tools Display Modes
Old   June 19, 2012, 03:30
Default Transient run taking too long time
  #1
New Member
 
Tham Keat Fu
Join Date: Jun 2012
Posts: 2
Rep Power: 0
Alexander Tham Keat Fu is on a distinguished road
Hi all.

My name is Alexander. I am running transient run for solid-liquid flow in a horizontal annulus.

I am facing a problem, which is my run is taking too long time. It sums up to 3 days and still running.

Previously, I have make changes in my setup as I read the related posts in this forum.

My current time step is of 0.001 s and my run is computed over a period of 100s. My model length is only 2 ft!!!

May I know what are the potential problems that I may have not identified in my setup?

Thank you very much.


Regards,
Alexander Tham
tham.keatfu@gmail.com
Alexander Tham Keat Fu is offline   Reply With Quote

Old   June 19, 2012, 14:48
Default
  #2
Senior Member
 
OJ
Join Date: Apr 2012
Location: United Kindom
Posts: 472
Rep Power: 10
oj.bulmer will become famous soon enough
Have you considered using adaptive time-stepping?

In case if you choose to use that, make sure you select a reasonable residual target and convergence criteria. If you select too stringent and aggressive convergence target (i.e. small), adaptive time-stepping takes very small time-steps, and convergence takes like aeons.

Also, running local parallel may help in speeding things up.

Regards
OJ
oj.bulmer is offline   Reply With Quote

Old   June 19, 2012, 21:11
Default
  #3
New Member
 
Tham Keat Fu
Join Date: Jun 2012
Posts: 2
Rep Power: 0
Alexander Tham Keat Fu is on a distinguished road
Thanks, OJ.

I will try using adaptive time step and let you know how is the progress. In addition to that, may I know in a normal transient simulation, how long would it takes?

Thanks. Appreciate your feedback.

Regards,
Alex
Alexander Tham Keat Fu is offline   Reply With Quote

Old   June 20, 2012, 06:53
Default
  #4
Member
 
Mauricio Labarca
Join Date: Aug 2009
Posts: 35
Rep Power: 7
mauricio is on a distinguished road
How long it'd take may depend on several things, the models that determine the amount of equations solved, the timestep size, the convergence criteria, the mesh resolution... Did you do a mesh sensitivity analysis to check you're not using a mesh that is too fine for this purpose?
mauricio 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
Problem: Very long "write" time (~2h-3h) for results and transient results Shawn_A CFX 14 March 11, 2014 09:38
Time step in transient simulation shib FLUENT 0 June 17, 2010 13:07
Superlinear speedup in OpenFOAM 13 msrinath80 OpenFOAM Running, Solving & CFD 17 August 22, 2009 03:59
Modeling in micron scale using icoFoam m9819348 OpenFOAM Running, Solving & CFD 7 October 27, 2007 00:36
Could anybody help me see this error and give help liugx212 OpenFOAM Running, Solving & CFD 3 January 4, 2006 18:07


All times are GMT -4. The time now is 02:22.