Hi Bernd, welcome back!
Concerning the change to pure SI units for Elmer, in some discussions, I imagined how the people fighting for SI 150 years back felt - some only see their use case.
Elmer boosts FreeCAD's simulation ability since it can do real multi-physics. For example solving Navier-Stokes equation in combination with thermal diffusion.
To be able to use this power one needs a proper unit systems so that the same Analysis leads to the same results on all PCs and, also important, that one can exchange his setup with others.
My favorite example is this one: (https://forum.freecadweb.org/viewtopic. ... d6#p604853)
* Voltage is in Volt:______kg·m2·s−3·A−1
* Conductivity is in S/m:_kg−1⋅m−3⋅s3⋅A2
* Permittivity is in F/m:__A·s·V−1·m−1
Following a unit scheme that uses another unit for the length than meter becomes a nightmare. And exactly for this the SI exists.
When I simulate e.g. a parallel plate capacitor and set one plate to 1V and the other one to 0V, I need to see a "1" as maximal voltage, not 1e6 or something depending on the unit system on a special PC.
Also when you have problems or collaborate with others, you need to share your case.sif file. Looking in the Elmer forum, you see that the vast majority of .sif files there use SI units.
All in all, now that it is in, some bugs in this regards could be fixed. As it is, Elmer is quite usable I hope and I am happy about this since selfish me , I use it and therefore spent many hours of spare time to bring it to the current state.
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My plans:
- enable multi-threading for Elmer. I think I succeeded just today with this: https://github.com/FreeCAD/FreeCAD/pull/7159
- this use case unveiled for example some missing features: https://forum.freecadweb.org/viewtopic. ... d6#p607368
(There are still some bugs in the handling of fluid materials. Also the fluid constraints are not in the shape as the other constraints. We don't have a constraint for a bulk pressure, e.g. the pressure of air in a vessel.)
- first when the first points are done, more Elmer features should be added (equations but also settings like the convergence level)
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What has been done for FC 0.20
- I tried to fix as many pipeline bugs as possible
- Werner made a great job in fixing issues and also polishing existing features
- almost all basic FEM features are now described in the Wiki
- https://wiki.freecadweb.org/Release_not ... _Workbench