Yes, this works. It seems that the instabilities result from the coupling. However, the time steps are extremely small (something like 0.1-0.01 s) and the Newton solver takes up to about 12 iterations to find out that it does not converge (and then reduces the time step). So I guess my great-grandchildren will be the first to see these results. My model domain is 3.2234e-3 x 1.44 and the aspect ratios of the discretization lengths (delta x/delta y) range from 6.25e-5 to 7e-3 ( for testing I use a very coarse grid). Could this be another reason for the instabilities?
Von: Dumux [mailto:[email protected]] Im Auftrag von Bernd Flemisch Gesendet: Mittwoch, 27. Mai 2015 12:58 An: DuMuX User Forum Betreff: Re: [DuMuX] Check for phase presence in the mpnc model Ok. Can you try to use your multidomain setting, but just don't couple by providing normal boundary conditions such as no-flux for each subdomain also at the coupling interface? Does this work? Since both SuperLU and Pardiso are direct solvers, I would not expect that one can solve a system that the other one cannot. Pardiso should work for the multidomain stuff and people that use it claim that it is faster than SuperLU. Bernd On 05/27/2015 12:47 PM, [email protected]<mailto:[email protected]> wrote: Hi Bernd, I already use SuperLU. Btw what about the PARDISO solver? Can it be used for multidomain applications and could this be an improvement? Kind regards Georg Von: Dumux [mailto:[email protected]] Im Auftrag von Bernd Flemisch Gesendet: Mittwoch, 27. Mai 2015 12:36 An: DuMuX User Forum Betreff: Re: [DuMuX] Check for phase presence in the mpnc model I don't understand why the linear solver should get into trouble by this modification. What linear solver do you use? If you use an iterative one, can you check if you run into an exception from the preconditioner when compiling with debug options, and also double-check by replacing the iterative solver with SuperLU? Kind regards Bernd On 05/26/2015 04:50 PM, [email protected]<mailto:[email protected]> wrote: By "the solver" I mean the linear solver. At least the values are correct. Maybe the numerical error from the coupling just gets too high if I use the old solution? Georg Von: Dumux [mailto:[email protected]] Im Auftrag von Bernd Flemisch Gesendet: Dienstag, 26. Mai 2015 16:29 An: DuMuX User Forum Betreff: Re: [DuMuX] Check for phase presence in the mpnc model Strange. By "the solver", do you mean the Newton or the linear solver? Can you check if the values in elemVolVarsPrev1/2 make sense? Bernd On 05/26/2015 03:53 PM, [email protected]<mailto:[email protected]> wrote: No, this does not work at all. The solver does not converge. Von: Dumux [mailto:[email protected]] Im Auftrag von [email protected]<mailto:[email protected]> Gesendet: Dienstag, 26. Mai 2015 15:47 An: [email protected]<mailto:[email protected]> Betreff: Re: [DuMuX] Check for phase presence in the mpnc model Hi Bernd, That's a good idea. I will try it and see what happens. Kind regards Georg Von: Dumux [mailto:[email protected]] Im Auftrag von Bernd Flemisch Gesendet: Dienstag, 26. Mai 2015 15:44 An: DuMuX User Forum Betreff: Re: [DuMuX] Check for phase presence in the mpnc model 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]<mailto:[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/> _______________________________________________ Dumux mailing list [email protected]<mailto:[email protected]> https://listserv.uni-stuttgart.de/mailman/listinfo/dumux -- _______________________________________________________________ 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> _______________________________________________________________ _______________________________________________ Dumux mailing list [email protected]<mailto:[email protected]> https://listserv.uni-stuttgart.de/mailman/listinfo/dumux -- _______________________________________________________________ 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> _______________________________________________________________ _______________________________________________ Dumux mailing list [email protected]<mailto:[email protected]> https://listserv.uni-stuttgart.de/mailman/listinfo/dumux -- _______________________________________________________________ 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> _______________________________________________________________ _______________________________________________ Dumux mailing list [email protected]<mailto:[email protected]> https://listserv.uni-stuttgart.de/mailman/listinfo/dumux -- _______________________________________________________________ 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> _______________________________________________________________ _______________________________________________ Dumux mailing list [email protected]<mailto:[email protected]> https://listserv.uni-stuttgart.de/mailman/listinfo/dumux -- _______________________________________________________________ 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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