Switching to DiffusionTermNoCorrection fixed it. Thanks!
On 03/07/2012 12:06 PM, Daniel Wheeler wrote:
Hi Justin,
Thanks for your interest in FiPy. Try switching the "DiffusionTerm" to
"DiffusionTermNoCorrection" and see if that improves things. I think
it will.
I can't run the example with version 2.1, I get an error when reading
the geo file. However, trunk works fine and converges to the right
answer (given first order error) for the unstructured case. I think
the major difference between trunk and version-2_1 is that
DiffusionTermNoCorrection is now the DiffusionTerm. If you make that
switch in your code you should be golden.
Cheers.
On Tue, Mar 6, 2012 at 3:16 PM, Justin Lazear <[email protected]
<mailto:[email protected]>> wrote:
Hi all,
I'm new to FiPy and FVA in general, and am excited to use it to
solve some thermal diffusion problems in my work. I figured before
I tackled a full-scale problem, I'd start small. Unfortunately I
was not very successful in this, and ran into an unexpected
problem with the solution diverging.
The problem I set up is the diffusion equation for a simple 3D
cylinder with square cross section and an aspect ratio of 2:1:1,
with BCs of -1 and 1 on the two opposite long ends.
This works fine using FiPy's built-in Grid3D (e.g. attached
script, fipytest5.py), and the solution happily approaches the
expected steady state. However, I will need to solve problems with
more complicated geometries, for which I expect to use gmsh. To
test gmsh, I created the same shape in gmsh (fipytest6.geo), let
gmsh handle the meshing, and let FiPy run on this mesh
(fipytest6.py), expecting essentially the same solution.
However, it's clear that the gmsh solution starts to diverge after
60 or so steps and continuing much beyond that gives a completely
nonsensical result. Reducing the step size does not help.
Increasing the mesh density makes the problem worse (it diverges
after fewer steps).
I've run the 2D version of this problem with both Grid2D and gmsh
meshes (in analogy with circle.py), and they work fine, so I seem
to be screwing up the transition to 3D.
Any insight would be greatly appreciated.
Versions:
In [283]: print sys.version
2.6.4 (r264:75706, Jun 4 2010, 18:20:31)
[GCC 4.4.4 20100503 (Red Hat 4.4.4-2)]
In [284]: print fipy.__version__
2.1.2
[~]$ uname -r
2.6.34.9-69.fc13.x86_64
[~]$ gmsh --version
2.5.0
Thanks,
Justin
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Daniel Wheeler
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