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Old   November 27, 2020, 07:25
Question Transient to steady state
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Hallo Foamers,

I am doing a leak simulation using rhoReatingBuoyantFoam, Which is a transient solver. I have to run like 30 cases with different velocities, and different leak flow rates. I have to run all the cases until 240 seconds so they are comparable. But, for some simulation cases that I am dealing with, they show steady behavior after some time like 20 seconds. In cases like this is it possible to switch simulation from transient to a steady-state automatically if there is no change in the respective field I am interested in. Transient for 240 seconds is taking days. As for some case variants, it's a complete waste of time to run after they reach a steady state. Changing ddt scheme from euler to steadyState gives an error. Can transient solvers be used in steady-state? I don't know, how people deal with this kind of stuff, how to proceed further, any ideas?

Please enlighten me if my question itself is wrong ?
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Old   December 3, 2020, 13:29
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Tamas Egeresi
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I would set the Co number as large as possible, depending on the stable solution. In this case, the solution would proceed with larger time steps, so it will reach the endTime much faster. I usually do this with pimpleFoam, so my guess is that it should work with rhoReactingBuoyantFoam as well.
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Old   December 3, 2020, 13:35
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Hai Tamas,
Thanks for the reply. I tried to use Co of 10, but for some cases, the quality of the solution, in my case cloud shape from the leak, is changing as I increase courant number. I know that a high courant number influences the quality of the solution. Apart from that, for cases with very less velocity's (like 1m/s leak), at high courant number, flow is not continuous and results are a little bit wierd.
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rhoreactinbuoyantfoam, steady, switch, transient

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