On Mon, Jan 28, 2013 at 4:21 PM, Salomon Turgman Cohen
<[email protected]>wrote:
> Hey Daniel,
> Apologies since this is probably basic stuff, but what do you mean with
> explicit, implicit, and coupled?
>
This has some explanation
http://en.wikipedia.org/wiki/Finite_difference_method
and also this FiPy example
http://www.ctcms.nist.gov/fipy/examples/diffusion/generated/examples.diffusion.mesh1D.html
In reality it comes down to a balance between the types of iteration
(whether time stepping, linear or non-linear iterations) in order to obtain
the best accuracy for the least effort.
Coupled refers to whether the equations are solved as independent equations
as far as the linear solutions are concerned or whether the solution
variables are combined into a single variable and solved with a single call
to the linear solver. Often better convergence can be achieved with coupled
solutions and some stability issues can be overcome (at least in my
experience). See
http://www.ctcms.nist.gov/fipy/examples/diffusion/generated/examples.diffusion.coupled.html
I see in the documentation the implicitsourceterm and I understand how to
> use that one. By explicit you mean just write the equation mathematically?
>
No. I mean to use an explicit source term. In FiPy that means not using a
term class at all to declare the term, just a variable or float. For
example,
TranisientTerm() == DiffusionTerm() + 2.
automatically uses an "_ExplicitSourceTerm" for the "2.". You could write
TransientTerm() == DiffusiionTerm() + _ExplicitSourceTerm(2.)
but you don't have to.
Cheers
--
Daniel Wheeler
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