Perhaps your errors in assigning the values are coming from the initial creation of the coefficients. I do recommend looking over the 1D diffusion example <http://www.ctcms.nist.gov/fipy/examples/diffusion/generated/examples.diffusion.mesh1D.html> carefully. Note that when declaring the coefficient for a diffusion term, it should be declared as a FaceVariable, not a CellVariable, as you've noted.
Ray On Tue, Sep 9, 2014 at 10:50 AM, John Assael <[email protected]> wrote: > Dear Raymond, > > Thank you for your fast reply. > > No I don't have that problem as my T variable represents the thermal > conductivity k, and it is not described in terms of position, it just > changes from material to material. > > Exactly rho * cp are the transient terms. > > Finally the equation results dT the temperature difference. > > What else could it be? > > Best regards, > John > On 9 Sep 2014 17:16, "Raymond Smith" <[email protected]> wrote: > >> Hi, John. >> >> I'm not completely sure if this is related, but I do want to make sure >> it's not something like that discussed in the recent thread about the heat >> equation on this list: >> >> http://thread.gmane.org/gmane.comp.python.fipy/3556/focus=3565 >> >> Is your "diffusion coefficient" (typically called alpha, thermal >> diffusivity, in heat transfer) a function of position? If so, it's >> important to keep only the thermal conductivity, k, as the coefficient for >> DiffusionTerm (more detail in the linked thread). The density and heat >> capacity should be coefficients for the TransientTerm. >> >> Cheers, >> Ray >> >> On Tue, Sep 9, 2014 at 10:00 AM, John Assael <[email protected]> wrote: >> >>> Hi, >>> I keep getting inaccurate results on my heat conduction experiment, 0.1 >>> missing accuracy except if the shape is extremely and abnormally dense. >>> In the beginning I though its the time steps but they are already very >>> small and make no difference if I shorten the intervals. >>> >>> I am trying to replicate a simulation from COMSOL and if I take the mesh >>> and the timesteps I cannot replicate the results accurately. >>> >>> I believe the problem is that all my variables are cell variables. >>> However, I read in the FAQ that diffusion terms have to be FaceVariables. >>> >>> More specifically, my mesh is 2-D and I have the following equation and >>> variables: >>> >>> * dT = CellVariable(name=r'$\Delta T$', mesh=mesh, value=0.)* >>> * Q = CellVariable(name=r'$Q$', mesh=mesh, value=0.)* >>> * T = CellVariable (name=r'$T$', mesh=mesh, value=0.)* >>> * D = CellVariable (name=r'$D$', mesh=mesh, value=0.)* >>> >>> * heat = (TransientTerm(coeff=D) == DiffusionTerm(coeff=T) + Q)* >>> >>> And then I go to the areas I have defined and set the values. Here is an >>> example of two of them. >>> >>> >>> * x, y = mesh.cellCenters meshW = (x ** 2 + y ** 2 <= >>> properties['r'] ** 2)* >>> * Q.setValue(properties['Q'], where= meshW)* >>> * T.setValue(properties['T'], where= meshW)* >>> * D.setValue(properties['D'], where= meshW)* >>> >>> * meshW1 = (x ** 2 + y ** 2 > properties['r'] ** 2)* >>> * T.setValue(properties['T1'], where= **meshW1**)* >>> * D.setValue(properties['D2'], where= **meshW1**)* >>> >>> However, when I do that I get an error for the face variable for every >>> single one I try to change. >>> Would sweeps instead of solve help me solve the problem? >>> Do you have any suggestions? >>> >>> Thank you very much! >>> >>> Best regards, >>> John >>> >>> >>> -- >>> ..:: ic3man.gr ::.. >>> software | design | development >>> _/_/_/ email : [email protected] >>> _/_/_/ www : http://www.ic3man.gr >>> ------------------------------------------------------------------ >>> This e-mail and any attachments are confidential. You may not copy >>> or disseminate any information contained in them to anyone other >>> than the intended recipient. If you are not the intended recipient >>> please contact the sender by reply e-mail and destroy all copies >>> of the original message immediately. >>> ------------------------------------------------------------------ >>> >>> _______________________________________________ >>> 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 ] >> >> > _______________________________________________ > 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 ]
