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simpleFoam convergence on large domain

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Old   May 15, 2011, 04:04
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Alberto Passalacqua
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Quote:
Originally Posted by maysmech View Post
Dear Alberto,
I have problem with LRR for hydrocyclone simulation yet. i used your suggested settings, it doesn't diverge but nor converge.
As you see in attached picture LRR result is not converge and it has wild fluctuations across its mean. i have set dynamic smagorinsky results (its figure is attached) as initial for LRR but after ten days and 14000 iterates its result is not acceptable and it decays initial too. its mesh is fine (1000000) and i don't think grids be the problem because LES answered proper results with same mesh. i have attached settings too.
Any idea would be appreciated.
Regards,
Maysam
Hi,

since the LES captures the flow properly, and it is an unsteady simulation (I assume you averaged the results in time), probably the steady solution is not representing the system properly (the flow in a cyclone is not strictly steady). You could try to run LRR in unsteady mode with pisoFoam to remove this doubt.

Best,
Alberto
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Old   May 22, 2011, 20:29
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Quote:
Originally Posted by alberto View Post
Hi,

since the LES captures the flow properly, and it is an unsteady simulation (I assume you averaged the results in time), probably the steady solution is not representing the system properly (the flow in a cyclone is not strictly steady). You could try to run LRR in unsteady mode with pisoFoam to remove this doubt.

Best,
Alberto
Dear Alberto,
I switched LRR from simpleFoam to pisoFoam.
It is strange for me but it gives good results with pisoFoam.
Thanks for your suggestion.
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Old   May 22, 2011, 21:23
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Quote:
Originally Posted by maysmech View Post
Dear Alberto,
I switched LRR from simpleFoam to pisoFoam.
It is strange for me but it gives good results with pisoFoam.
Thanks for your suggestion.
Good! This confirms that the flow is not steady, and you need to resolve it in time, which is not possible with simpleFoam. If possible, try to make a movie of the flow: you will probably notice that, even after a long time, it never reaches a fully steady condition.

Best,
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Old   May 31, 2013, 10:10
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Originally Posted by askjak View Post
I would suggest to run a couple of hundreds of steps without turbulence (set "turbulence" to "off" in constant/RASProperties). Then turn it "on" while the simulation is running.

If it does not initial converge without turbulence generate an initial field from "potentialFoam -writep"

-Ask
hi askjak
would you please explain more, that how could generate an initial field from potentialFoam?
thank you very much
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