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

false time step implementation for steady state

Register Blogs Community New Posts Updated Threads Search

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   June 17, 2008, 23:34
Default false time step implementation for steady state
  #1
Kushagra
Guest
 
Posts: n/a
Hello All,

Convergence for the steady state simulations can be obtained by decreasing the 'false time step'.

Keeping the default RMS convergence criteria (10^-4) for the steady state simululation, convergence in my simulation became difficult to achieve after a while and hence I changed the 'Timescale Factor' from 1 to 0.01 [in the pannel Solver Control -> Basic Settings -> Convergence Control ->Fluid Timescale Control].

It resulted in decreasing the auto time scale from 2*10^-2 to 2*10^-4 and I achieved the convergence.

I do not have a understanding of how the steady solver works (using a 'false' time step)? Could you please help me in understanding the affect/effect of high/low false time step on the accuracy of results.

And what convergence criteria should I use for the problems like cyclone?

With very kind regards, Kushagra
  Reply With Quote

Old   June 22, 2008, 20:06
Default Re: false time step implementation for steady stat
  #2
Glenn Horrocks
Guest
 
Posts: n/a
Hi,

How timestepping works is described in the documentation.

As for what convergence criteria you need, that is problem dependant and you should do a sensitivity study to check it. There is also a guide on convergence levels in the documentation.

Glenn Horrocks
  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
Floating point exception error Alan OpenFOAM Running, Solving & CFD 11 July 1, 2021 22:51
Time step, Number of time step, Maxximum Iterations per time step sandisk FLUENT 0 July 18, 2011 03:57
IcoFoam parallel woes msrinath80 OpenFOAM Running, Solving & CFD 9 July 22, 2007 03:58
False time step factors Jesper Laursen Main CFD Forum 4 June 4, 2002 05:35
unsteady calcs in FLUENT Sanjay Padhiar Main CFD Forum 1 March 31, 1999 13:32


All times are GMT -4. The time now is 11:58.