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Old   September 8, 2012, 09:35
Question About changing time step at the CFX-solver
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Meimei Wang
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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.
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Old   September 8, 2012, 13:57
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Yes there is a button to edit the run in progress.
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Old   September 9, 2012, 06:22
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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.
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Old   September 15, 2012, 18:08
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Quote:
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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.
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Old   September 15, 2012, 18:23
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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.
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Old   September 16, 2012, 04:50
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Quote:
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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?
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Old   September 16, 2012, 07:47
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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.
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