PR 7100: FEM WB Elmer viscosity bug fix

About the development of the FEM module/workbench.

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uwestoehr
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Re: PR 7100: FEM WB Elmer viscosity bug fix

Post by uwestoehr »

uwestoehr wrote: Mon Oct 24, 2022 12:40 pm What remains is the problem that when I use water instead of air as fluid, there is no convergence. I tried hard but get no setup where water works. Do you?
Meanwhile I wrote the documentation of the Flow equation:
https://wiki.freecadweb.org/FEM_EquationFlow

But I did not yet have time to check what settings would be necessary to find a converging solution when water is used as fluid.
mst31
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Re: PR 7100: FEM WB Elmer viscosity bug fix

Post by mst31 »

Hello! Sorry for very long answer. Now I want to continue investigation of Elmer. But last version of FreeCAD (commit e188802ca6997d2564e7570ab648462e6a059f87) goes wrong trivially zero result. I tried my example that before worked fine. Also I created simple Flow example and it also has this problem. Have you any ideas about this problem?
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tube.FCStd.7z
Simple Flow Elmer example
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RichB2k
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Re: PR 7100: FEM WB Elmer viscosity bug fix

Post by RichB2k »

Hello,

Sounds like an Elmer issue with mesh names, as described here:

http://www.elmerfem.org/forum/viewtopic ... 404#p27404

Try installing a new version of Elmer?

Rich.
mst31
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Re: PR 7100: FEM WB Elmer viscosity bug fix

Post by mst31 »

Thank you! New version of Elmer solved this issue.
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uwestoehr
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Re: PR 7100: FEM WB Elmer viscosity bug fix

Post by uwestoehr »

For information. I added the simple (2D) flow example to the FEM examples for the next release:
https://wiki.freecad.org/FEM_Examples
You can try this out with the latest Weekly build: https://github.com/FreeCAD/FreeCAD-Bund ... taller.exe
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uwestoehr
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Re: PR 7100: FEM WB Elmer viscosity bug fix

Post by uwestoehr »

I have great news because now you can specify a velocity profile for flow simulations, see the description here: https://wiki.freecad.org/FEM_ConstraintFlowVelocity
(Note that you must setup new flow constraints for existing analyses because of the new functionality.)

I also fixed bugs that made _every_ flow simulation result wrong: the density and the viscosity were taken with a factor 1000 too high.
Therefore please don't trust the results you obtained so far with flow analyses!

Here is a build that includes this feature and the fixes:
https://github.com/FreeCAD/FreeCAD-Bund ... taller.exe
mst31
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Re: PR 7100: FEM WB Elmer viscosity bug fix

Post by mst31 »

uwestoehr, thank you a lot of! I will try it.
thschrader
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Re: PR 7100: FEM WB Elmer viscosity bug fix

Post by thschrader »

uwestoehr wrote: Sun Mar 26, 2023 8:30 pm ...
Here is a build that includes this feature and the fixes:
https://github.com/FreeCAD/FreeCAD-Bund ... taller.exe
Do you have a simple zip-package too?
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