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[cutejeff <question107819@xxxxxxxxxxxxxxxxxxxxx>]

Question #107819 on DOLFIN changed:
https://answers.launchpad.net/dolfin/+question/107819

    Status: Answered => Open

cutejeff is still having a problem:
Thank you for your help.

The PDE was derived using conservation of mass, but the results from
Fenics showed the mass actually kept growing with time. Because my
finite difference code doesn't grow, I consider my finite element code
got some problems somewhere.

Interestingly, if I get rid of the (du/dx)^2 term in both Fenics and my
finite difference code, the results match each other. Because I haven't
seen any examples on manipulating the power of derivatives, I think it
might be the cause. I don't think I can take integration by parts for
v*(du/dx)^2*dx,  I don't know what to do with it, except keep it in this
way.

I also tried the convergence study, it's getting a little better if I
improve the mash refinement and the polynomial degree. But it doesn't
change much, the mass still grows.

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