About changing time step at the CFX-solver

Anna Tian · September 8, 2012, 09:35

Hi,

May I ask if there's any way to change the time step at the CFX-solver? So that when I want to change the time step to let the RMS converge I can stop the simulation and change it directly without going back to CFX-pre. Then start the running again with the result before changing the time step as the initial data.

Thank you very much.

cdegroot · September 8, 2012, 13:57

Yes there is a button to edit the run in progress.

ghorrocks · September 9, 2012, 06:22

For a stady state run use the edit run in progress option in the solver manager. For a transient state run use adaptive time stepping, converging on 3-5 coeff loops per iteration.

Anna Tian · September 15, 2012, 18:08

Quote:

Originally Posted by ghorrocks

For a stady state run use the edit run in progress option in the solver manager. For a transient state run use adaptive time stepping, converging on 3-5 coeff loops per iteration.

Thanks! But is there a way that I can set the change in advance and change it automatically during the running? Like I can set when the convergence stop, it changes its time step to another value. Or when it reaches a time step number (for example, like 500), it changes to another.

cdegroot · September 15, 2012, 18:23

Yes you can give multiple timesteps. See the section of the CFX manual entitled "Transient Timestep Control". You can give a comma separated list, but in your case it's probably better to write an expression that gives the timestep.

Anna Tian · September 16, 2012, 04:50

Quote:

Originally Posted by cdegroot

Yes you can give multiple timesteps. See the section of the CFX manual entitled "Transient Timestep Control". You can give a comma separated list, but in your case it's probably better to write an expression that gives the timestep.

Thanks. But I work on the steady-state flow. And I always would like to change my time step from local time step of factor 5 to physical time step of 10^-4 in the middle of the simulation (when RMS doesn't decrease any more). How to make it changes automatically?

ghorrocks · September 16, 2012, 07:47

Set it up as two runs, one which does the local time step bit and a second which uses that as an initial condition for a physical time step run. The automate is by using a batch/script file so you can run it all from a single command.

September 8, 2012, 09:35	About changing time step at the CFX-solver	#1
Anna Tian Senior Member Meimei Wang Join Date: Jul 2012 Posts: 494 Rep Power: 16	Hi, May I ask if there's any way to change the time step at the CFX-solver? So that when I want to change the time step to let the RMS converge I can stop the simulation and change it directly without going back to CFX-pre. Then start the running again with the result before changing the time step as the initial data. Thank you very much. __________________ Best regards, Meimei

September 9, 2012, 06:22		#3
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,934 Rep Power: 145	For a stady state run use the edit run in progress option in the solver manager. For a transient state run use adaptive time stepping, converging on 3-5 coeff loops per iteration. Nurzhan likes this.

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Reading forces from previous time step within solver	SD@TUB	OpenFOAM Programming & Development	5	April 24, 2023 11:51
High Courant Number @ icoFoam	Artex85	OpenFOAM Running, Solving & CFD	11	February 16, 2017 13:40
InterFoam negative alpha	karasa03	OpenFOAM	7	December 12, 2013 03:41
CFX Post: Problems with moving point cloud for changing time steps	spatialtime	CFX	0	December 7, 2009 04:56
Small time step and CFX solver crashing	Vanessa	CFX	2	June 21, 2006 09:18

September 8, 2012, 13:57		#2
cdegroot Senior Member Chris DeGroot Join Date: Nov 2011 Location: Canada Posts: 414 Rep Power: 18	Yes there is a button to edit the run in progress.

September 15, 2012, 18:23		#5
cdegroot Senior Member Chris DeGroot Join Date: Nov 2011 Location: Canada Posts: 414 Rep Power: 18	Yes you can give multiple timesteps. See the section of the CFX manual entitled "Transient Timestep Control". You can give a comma separated list, but in your case it's probably better to write an expression that gives the timestep.

September 16, 2012, 07:47		#7
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,934 Rep Power: 145	Set it up as two runs, one which does the local time step bit and a second which uses that as an initial condition for a physical time step run. The automate is by using a batch/script file so you can run it all from a single command.