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false time step implementation for steady state

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Old   June 17, 2008, 22:34
Default false time step implementation for steady state
  #1
Kushagra
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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
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Old   June 22, 2008, 19:06
Default Re: false time step implementation for steady stat
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Glenn Horrocks
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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
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