Select inner faces as FEM boundary

[HoWil]

Good afternoon,

I want to use FC to build a mesh for an external FEniCS model.
Therefore, I need to select faces in order to set boundary groups while I use the new GMESH feature in FEM-WB. The single domain of the model is a box with a cutted sphere in the center and looks like in the following pic:

Screenshot from 2016-11-28 16-06-41.png (178.34 KiB) Viewed 3342 times

I want now to select the inner, spherical faces to use them for a boundary condition. How do I select them?
Is it possible to hide one of the outer faces to see inside the box?

Thanks in advance,
HoWil

[ulrich1a]

I want now to select the inner, spherical faces to use them for a boundary condition. How do I select them?

I think Bernd coded it that way, that you can just use the sphere of your model to set the inner boundery.
So you need only to hide the Box and unhide the Sphere, in order to select the surface of the Sphere for your boundery condition.

Ulrich

[ickby]

Hello,

I think the only option you have is to use clipping planes. Go to View->clipping Plane and than simply select the inner face. However, as the plane settings open in the tasks panel and all clipping planes vanish on close it cannot be used parallel to annother open task. so this only works if it is enough to preselect a face before running a fem tool.
It is a point on my neverending list to make the cpliping planes a own dock widget, but I dod not yet manage to find the time for it.

[HoWil]

you can just use the sphere of your model to set the inner boundery

Basically there is no sphere; I used the 'Subtractive Sphere' feature in Part-Design-Next (PDN).
I think in PDN it is not possible to draw more than one 'bodies' like a box (from the additive primitive pull down menu) and a sphere in one PDN-body.
Thx

[HoWil]

Hello,

I think the only option you have is to use clipping planes. Go to View->clipping Plane and than simply select the inner face. However, as the plane settings open in the tasks panel and all clipping planes vanish on close it cannot be used parallel to annother open task. so this only works if it is enough to preselect a face before running a fem tool.
It is a point on my neverending list to make the cpliping planes a own dock widget, but I dod not yet manage to find the time for it.

Now I at least know this feature even if I can't use it .
I did see it before but did not know how to enable it.

[HoWil]

Any further ideas??
Thx in advance,
HoWil

[ulrich1a]

I got it. There is the quick and dirty way with the python console.
First find out the face number of the inner sphere. This can be done with cut-view. You will find the face name in the bottom of the FreeCAD-Window.
Now make your constraint and use any face you want. Have a look into the python console. There you will find a line like this:

Code: Select all

App.ActiveDocument.FemConstraintPressure.References = [(App.ActiveDocument.Sphere,"Face5"))

Use the edit-feature of the python console to get again that line. (use the up-arrow)
Edit this line and put the right face-number in.
With return you are done.

Ulrich

[HoWil]

@Ulrich1a
Thank you very much. Worked like a charm.

[HoWil]

Is there maybe also a command for selecting a face/domain via coordinates or an intersecting box?

[bernd]

I missed the topic but ulrich posted an answer to the problem already.

I addition two more possibilities.

Arch --> Section Plane --> See post viewtopic.php?t=15183&start=10#p121641

or

Draft --> Downgrade --> See topic viewtopic.php?t=12381

If it is one one or two faces I would use the python command.