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How to stop transient solver when steady state is reached?

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Old   March 24, 2020, 09:58
Default How to stop transient solver when steady state is reached?
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james freak
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Hi,
If I am running a simulation with a transient solver for lets say 1s and the steady state solution is reached at 0.1s, how to tell the solver to stop and not spend a lot of time computing things I'm not interested in ?

Is there a way to automatically do that, for example with a condition on residuals?
Thank you.
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Old   March 26, 2020, 04:58
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Alexey Matveichev
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Hi,

You can use codedFunctionObject for this purpose. Take residuals function object (example of how to get residual values) and abort (example of how to stop simulation) as an inspiration and make your own.
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Old   March 26, 2020, 10:22
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ok thank you I will try that
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Old   March 29, 2020, 11:17
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Ruiyan Chen
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Monitoring the residuals as pointed out by Alexey can do the trick, but I do think you have to think more about it. Sometimes, just by monitoring the residuals is not enough, and would even give you wrong indication. What I normally do is to set up several probes inside the domain (you can do this during run time) and monitor pressure and velocity there. If the probe values become stable, it's a good indication that the simulation may have reached steady-state. Or you can monitor minimum and maximum values of say pressure, temperature and so on, if their values become stable, it's a good sign as well.
But keep in mind, these still can not tell you the whole picture. If you have walls, typically what people do is to monitor the forces applied by the fluid on the wall, they are better indications of whether the flow has reached steady-state.
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