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Tobias
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Thermal PDE in cylindrical coordinates at the origin

Asked by Tobias
on 11 Jan 2019
Latest activity Answered by Svetlana Pease on 18 Jan 2019
Hi,
I have a problem with a thermal PDE in cylindrical coordinates. I followed the example in Heat Distribution in Circular Cylindrical Rod .
The script runs without errors, however the solution has peculiar spot at z = 0, r = 0 where the Temperature is constantly zero. The heat source at that spot is well larger than zero and all around the spot a temperature which is as expected is reached.
I tried changing several of the pde SolverOptions or choose the mesh differently, however nothing of what I tried was successful.
Does anybody have an idea what I can do to fix this issue?
Thanks in advance

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2 Answers

Answer by Svetlana Pease on 11 Jan 2019

Hi Tobias,
Are you talking about the steady-state or transient solution? The only zero temperature I get is for the transient solution at t = 0 (time step is 1 for t = 0).
Regards,
Svetlana Pease
MathWorks Documentation Group

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I already had Hmax at 1e-4 which however did not help. Smaller Hmax made my PC run out of memory.
What helped a bit was however a rescaling of the whole problem by multiplying all lengths by 1000. I should also be able to achieve this by setting some absolute solverOptions but I have not looked into it yet.
Is there a possibility to create the mesh with two different Hmax? I naively tried to assembly the mesh in two steps but I was not allowed to change the read-only FEMesh.
If I calculate my problem in full 3d the problem does not appear (however I cannot choose my grid fine enough to get rid of other oscillations)
I'd simply start with the geometry at r = eps instead of r = 0 for eps being a small value.

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Answer by Svetlana Pease on 18 Jan 2019

Hi Tobias,
No, there is no option to have two or more Hmax settings for the same geometry/mesh.
Regards,
Svetlana

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