Thanks for your interest in FiPy

On Mon, Oct 16, 2017 at 6:16 PM, F Hssn <> wrote:
> So my questions are:
> - Does fipy handle anisotropic unstructured meshes without any
> problem? (I'm specifically looking to use bamg for 2D mesh adaptation
> based on interpolation error reduction/equidistribution)

What is an anisotropic mesh?

FiPy does "handle" unstructured meshes in that the problem will solve,
however, the accuracy decreases as the non-orthogonality and
non-conjunctionality increases (as you pointed out). There has been an
attempt to implement terms to correct for the non-orthogonality, see


You might want to try playing with the corrected diffusion term to see
how well it works. I can't find any examples of its use though.

See also


> - If not, does fipy provide (or provide a way to implement) MPFA
> (multi-point flux approximation) or some other non-classical scheme
> (like HMM) that allows anisotropic unstructured meshes (as discussed
> in the Drioniou paper [1]) ?

I don't think I can easily answer that without a great deal of work,
but I did skim over the Drioniou paper, I can't foresee all the issues
with implementing the various schemes but one that does come to mind
is having to use neighbor's neighbor values to compute fluxes, which I
think these schemes require. It would require a lot of changes to FiPy
to set that up efficiently. However, I will certainly keep this paper
on my list of items to research further. Thanks for highlighting it.

> - Or, does fipy allow any other way to make vertex-centered control
> volume calculation that can take into account anisotropy and can make
> sure there are no control volume overlaps (and as a result, the
> coefficients stay positive, and monotonicity is maintained, and none
> of the nice properties are violated) ?

No, FiPy is definitely not set up for vertex centered. The above
cell-centered approach is the way to go.

Daniel Wheeler
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