Hi Georg,
you could try to check for the phase state depending on the solution
from the old _time_ step. If you have an infrastructure similar to the
current multidomain models, you should have CParams which offer access
to the old values via elemVolVarsPrev1/2.
Kind regards
Bernd
On 05/26/2015 03:33 PM, [email protected] wrote:
Hi Bernd,
I checked for the phase presence in the evalCoupling function of my
localoperator-file. Here I couple the water component balance of the
mpnc model to my membrane model by setting CouplingOutflow boundary
conditions for the membrane and CouplingInflow for the mpnc domain. As
I neglect miscibility in the membrane (I assume pure water here), I
set the activity of water in the membrane to 1 if the liquid phase is
present. Checking for the water saturation for the phase presence
caused numerical problems which did not occur when I use the sum of
mole fractions in the liquid phase instead. Now that I write it down
it puzzles me even more… Anyway, the appearance of the liquid phase
during startup of a fuel cell combined with the coupling to the
membrane transport is numerically really challenging and I need to
work on this topic some more. If I obtain some reliable results I will
be glad to share them with you.
King regards
Georg
*Von:*Dumux [mailto:[email protected]] *Im
Auftrag von *Bernd Flemisch
*Gesendet:* Dienstag, 26. Mai 2015 15:06
*An:* DuMuX User Forum
*Betreff:* Re: [DuMuX] Check for phase presence in the mpnc model
Hi Georg,
On 05/22/2015 08:24 AM, [email protected]
<mailto:[email protected]> wrote:
Hello DuMuX,
I started working with the mpnc model and I wonder how I can check
for the phase presence. Just accessing the phase saturation does
not seem to be a safe way since during newton iterations the value
may differ from zero even though the phase is not present (am I
right here?). Right now I check if the sum of all mole fractions
in the phase of interest is equal to 1. This seems to work,
however I wonder whether I should include a threshold (something
like: sumMolefractions[phaseIdx] > 1 – eps_). Or is there a better
way?
I am not sure if one criterion is better than the other. Before the
Newton converges, values for saturations can be "wrong", but so can
the values for the mole fractions. If a solution at some Newton
iteration shows a positive saturation value, then the corresponding
phase is present for this solution. However, values may change for the
converged solution. So I would be careful with making decisions based
on intermediate solutions.
Can you describe in more detail what you mean by "This seems to work"?
Does it not work with checking the saturation values?
Kind regards
Bernd
Thanks for your help
Georg Futter
——————————————————————————
*German Aerospace Center *(DLR)
Institute of Engineering Thermodynamics | Computational
Electrochemistry | Pfaffenwaldring 38-40 | 70569 Stuttgart
Dipl.-Ing. *Georg Futter* | Ph.D. student
Telefon 0711/6862-8135 | [email protected] <mailto:[email protected]>
www.DLR.de <http://www.dlr.de/>
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_______________________________________________________________
Bernd Flemisch phone: +49 711 685 69162
IWS, Universität Stuttgart fax: +49 711 685 60430
Pfaffenwaldring 61 email:[email protected]
<mailto:[email protected]>
D-70569 Stuttgart url:www.hydrosys.uni-stuttgart.de
<http://www.hydrosys.uni-stuttgart.de>
_______________________________________________________________
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--
_______________________________________________________________
Bernd Flemisch phone: +49 711 685 69162
IWS, Universität Stuttgart fax: +49 711 685 60430
Pfaffenwaldring 61 email: [email protected]
D-70569 Stuttgart url: www.hydrosys.uni-stuttgart.de
_______________________________________________________________
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