What's happening with residuals?

plm · January 22, 2012, 13:58

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,
plm

zhernadi · January 27, 2012, 01:39

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.

Zoltan

plm · January 27, 2012, 03:21

Zoltan,
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.

Cheers
plm

January 27, 2012, 01:39	fvSolution	#2
zhernadi New Member Zoltan Hernadi Join Date: Jul 2010 Posts: 12 Rep Power: 15	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. Zoltan

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January 27, 2012, 03:21		#3
plm New Member RW Join Date: Nov 2011 Posts: 22 Rep Power: 15	Zoltan, 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. Cheers plm