The vector formulation is still rather slow (much much slower than with just one equation). Is that expected? On Jan 14, 2014 12:10 PM, "Guyer, Jonathan E. Dr." <[email protected]> wrote:
> Coupled Cahn Hilliard has known problems: > http://matforge.org/fipy/ticket/582 > > I don't know whether the issues described in that ticket are the source of > what you're seeing, but it can't help. For your problem, you may want to > base what you're doing on the vector formulation in that example. > > On Jan 14, 2014, at 11:31 AM, Jane Hung <[email protected]> wrote: > > > Update: The mesh2DCoupled example did work, but I had to change the grid > dimensions make it look like the pictures online. However, it's also > incredibly slow. I left it running overnight and it only reached elapsed > time of about 0.6. It being so slow for a simple system may explain why it > can't deal with my more complicated coupled system. Is this expected > behavior? Is there any way to speed things up so that my system has a > chance of running at all? > > > > > > On Mon, Jan 13, 2014 at 2:11 PM, Jane Hung <[email protected]> wrote: > > Yes, restricting the time step works. However, whenever I split up the > equation (like d(phi)/dt = Xi, Xi= laplacian(phi)), it is never able to run. > > > > Also, when I run the Cahn-Hilliard mesh2DCoupled example, the results > are that the concentration becomes more and more homogeneous rather than > phase separation. This is very different than the expected results shown on > the examples page (which is what I get when turning the 3 equations into > just 1 equation) > > > > On Jan 11, 2014, at 9:07 AM, Guyer, Jonathan E. Dr. < > [email protected]> wrote: > > > >> It looks to be stable up to time steps of about 25. You are using the > exponentially increasing stepper from our Cahn Hilliard examples, which are > unconditionally stable (and we have them top out at 100). Because of the > explicit terms in your splitting, you should keep your time steps below the > stability limit. > >> > >> FYI: dropbox is completely blocked from our DNS servers at NIST. I > happened to see your message at home, so could download the movie > independent of the NIST network, but that's not normally true. If you have > large files to share with us in the future, let us know and we can provide > a place to put them. > >> > >> > >> On Jan 10, 2014, at 11:23 AM, Jane Hung <[email protected]> wrote: > >> > >>> I tried to start with a simpler system, and it seems like I get the > same problem if I split up the equations at all. > >>> > >>> Anyway, I started with a 1 equation system > http://pastebin.com/X5tT1RUB and would like to see the phase separation, > but after time ~2000 (see the video > https://www.dropbox.com/s/nocwmh8x1f5b6rw/1_order_parameter.mp4), the > error increases a lot. I'd like to see what happens after more iterations, > so is there a way to keep the error small? > >>> > >>> > >>> On Mon, Dec 30, 2013 at 10:50 AM, Daniel Wheeler < > [email protected]> wrote: > >>> On Sun, Dec 29, 2013 at 6:28 PM, Jane Hung <[email protected]> wrote: > >>>> I'm also getting RuntimeError. To get over this, is there a way to > represent > >>>> the system a different way or does the system itself too complicated? > >>> > >>> You can also represent the system in an entirely uncoupled manner. > >>> That would reduce the size of memory and provide an alternative > >>> result. If the time step is small enough the uncoupled and coupled > >>> formulations should be the same. > >>> > >>>> What do you mean by know the answer? > >>> > >>> I just meant some analytical result or behavior such as bounded values > >>> or conserved quantities. A demonstrable logical inconsistency makes > >>> debugging easier. > >>> > >>>> I have an idea of what the time > >>>> evolution of the variables should look like in the 2D case, but I > don't have > >>>> an analytical solution. > >>> > >>> That helps. Could you hold some of the variables fixed (by changing > >>> coefficient values or time steps for some equations) and then evolve > >>> only one or two of the equations for example. > >>> > >>> -- > >>> Daniel Wheeler > >>> _______________________________________________ > >>> fipy mailing list > >>> [email protected] > >>> http://www.ctcms.nist.gov/fipy > >>> [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ] > >>> > >>> > >>> > >>> -- > >>> Jane Hung > >>> Graduate Student | MIT Department of Chemical Engineering > >>> Hatton Lab 66-325 | Doyle Lab E18-509 > >>> [email protected] | 415.952.6325 > >>> _______________________________________________ > >>> fipy mailing list > >>> [email protected] > >>> http://www.ctcms.nist.gov/fipy > >>> [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ] > >> > >> > >> _______________________________________________ > >> fipy mailing list > >> [email protected] > >> http://www.ctcms.nist.gov/fipy > >> [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ] > > > > > > > > > > -- > > Jane Hung > > Graduate Student | MIT Department of Chemical Engineering > > Hatton Lab 66-325 | Doyle Lab E18-509 > > [email protected] | 415.952.6325 > > _______________________________________________ > > fipy mailing list > > [email protected] > > http://www.ctcms.nist.gov/fipy > > [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ] > > > _______________________________________________ > fipy mailing list > [email protected] > http://www.ctcms.nist.gov/fipy > [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ] >
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