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What's happening with residuals?

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Old   January 22, 2012, 14:58
Default What's happening with residuals?
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Hey all,
This may sound like a really silly question, but I'm wondering if someone can take a look at the attached file and tell me what's happening with residuals.

I don't really understand how something can converge like this and then the solution get worse and get stuck at the end...?

Is this a consequence of my particular case setup or is there a more general reason? Is this even a problem, or are my results from the point of most converged valid?

Hoping someone can shed some light on this.
Thanks in advance,
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File Type: jpg residuals.jpg (33.4 KB, 45 views)
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Old   January 27, 2012, 02:39
Default fvSolution
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Zoltan Hernadi
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Hello RW,

I think your simulation is converged based on the convergence criteria. In some OpenFOAM tutorials, the default convergence criteria are using absolute tolerances of 1e-5 or 1e-6, so equations will not be solved if the initial residuals are below these thresholds. However, these settings can be changed in system/fvSolution for every variables with the 'tolerance' setting.

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Old   January 27, 2012, 04:21
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Thanks for the reply.
I am a bit dubious about the above results and don't really trust them myself but wondered what anyone else had to say about it.

I managed to get this case to converge 'properly' (i.e. without going back up at the end) by increasing the relaxation of pressure.

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