FEM patches against FreeCAD 0.20.1

About the development of the FEM module/workbench.

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uwestoehr
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FEM patches against FreeCAD 0.20.1

Post by uwestoehr »

Dear FEM community, FreeCAD 0.20.1:
brought many improvements for FEM, especially the result pipe system and Elmer.

However, bugfixing goes on since our active community reports issues.

In order that you do not have to want some months to benefit from the recent fixes, I will publish here a package with patched files as ZIP. To benefit from the recent fixes, the workflow is this:
- install FreeCAD 0.20.1
- extract the ZIP to the folder "~\Mod\Fem" of your FreeCAD installation folder (overwrite thereby the existing files)

Please report issues your have for the patches to this thread.

----------------

initial release: 13-08-2022:
Elmer-fixes-based on FC 0.20.1-13-08-2022.zip
(40.03 KiB) Downloaded 49 times
fixes: new:
  • Elmer: support to disable the linear solver system.
    Assuming your have an analysis with 3 different equations and you want to turn off one for testing, you can set the equation property "LinearSystemSolverDisabled" to true and the solving of this equation will not be performed.
    git commit 7d9855c8
  • add support for the preconditioner "ILUT"
    git commit 7d9855c8
    (By the way, for flow simulations, I found out that the preconditioner matters. For Diagonal and ILUT there is no convergence. ILU1 was the best.)
  • add support for the iterative solver method "Idrs"
    git commit 7d9855c8
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Re: FEM patches against FreeCAD 0.20.1

Post by uwestoehr »

For those who try our Elmer:

* if you have troubles that your setup does not allow the solver to converge, change the relaxation factor:
https://wiki.freecadweb.org/FEM_SolverE ... ear_System
This applies only for nonlinear systems like the Flow and the Heat equation, especially when both equations are combined.

* if you perform stress analyses, checkout the brand new Wiki documentation:
https://wiki.freecadweb.org/FEM_EquationElasticity
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Re: FEM patches against FreeCAD 0.20.1

Post by uwestoehr »

second release: 14-08-2022:
Elmer-fixes-based on FC 0.20.1-14-08-2022.zip
(38.9 KiB) Downloaded 38 times
changes since initial release
fixes:
  • fix for the "Idrs" iterative solver method: git commit d8784b7a
    The Idrs method is for flow simulations in 3D about 15 % faster than the the default iterative method "BICGstab". In 2D ist is even 30% faster. Here is a 2D testcase that you can test this out by yourself:
    FlowStep-Air-2D.fcstd
    (42.32 KiB) Downloaded 50 times
    This is the result:
    FreeCAD_9Vxamelq23.png
    FreeCAD_9Vxamelq23.png (54.29 KiB) Viewed 8081 times
  • make the initial flow constraint properly working: git commit dd370b96
    The initial flow only makes sense for fluid materials. Furthermore you can now setup an initial flow to every fluid material in the analysis and not just one for all.
  • fix handling of the vacuum permittivity constraint: git commit 9db5dff7 and git commit e2636b29
    Not that I believe anybody really wants to overwrite the vacuum permittivity :) , but the constrain at is was, was handled wrong. Now our electrostatics example file issues no warning anymore.
new:
  • Elmer: support pressure acting on faces of fluids: git commit dce15245
    The existing pressure constraint is also applicable for fluids. it was just not yet taken into account.
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Re: FEM patches against FreeCAD 0.20.1

Post by uwestoehr »

third release: 17-08-2022:
Elmer-fixes-based on FC 0.20.1-17-08-2022.zip
(41.93 KiB) Downloaded 61 times
(all fixes from previous releases are included)

fixes since the previous release: Here is a small example showing the full capacity of the Flux equation:
Flux-Example.FCStd
(315.28 KiB) Downloaded 40 times
FreeCAD_ZNRw83HrnR.png
FreeCAD_ZNRw83HrnR.png (70.22 KiB) Viewed 7927 times
(potential flux in a cube)


By the way, since FreeCAD 0.20.1 you can perform also transient simulations with Elmer. Check this out and see this Wiki page for more info how:
https://wiki.freecadweb.org/FEM_SolverE ... ngs#Solver
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