## FEM-Hydrostatic pressure constraint help/request

About the development of the FEM module/workbench.

Moderator: bernd

-alex-
Posts: 241
Joined: Wed Feb 13, 2019 9:42 pm
Location: France

### Re: FEM-Hydrostatic pressure constraint help/request

paul18 wrote:
Sat Jul 13, 2019 4:31 pm
you've to find the right values so that the force is the one resulting from the hydrostatic pressure, haven't you?
Thanks Paul for your attention to this topic. As far as I understand I can use the actual Dload pressure system witch already balances forces on nodes accordingly to the surface of mesh faces.
Then I need to weigh the pressure with a factor = rho*G*H accordindly to the altitude of each face of mesh from the initial surface witch is the height reference.
If this strategie involves to deal with C language I think I will fail because of my lack of skills.
As Bernd said, maybe a macro would be easier and faster to developpe , furthermore suitable with my very limited skills in programing.
I have to read and learn a lot before to ask more questions and advices. Now I'm not at home and I access the forum with smartphone so it's not convenient to make some progress.
To be continues...
Any advice and opinion still appreciated
HarryvL
Posts: 1052
Joined: Sat Jan 06, 2018 7:38 pm

### Re: FEM-Hydrostatic pressure constraint help/request

Alex, the translation of pressure to nodal forces is taken care of by Calculix. This is quite involved for curved surfaces. If you want to see how it is done you can have a look at the fcFEM source code. However, as I said, this should not be necessary. The DLOAD card only requires the pressure and the ID of the faces the pressure is applied to. So some math and some admin at the stage of writing the DLOAD “card” (yes, I still used them )
Kunda1
Posts: 5903
Joined: Thu Jan 05, 2017 9:03 pm

### Re: FEM-Hydrostatic pressure constraint help/request

HarryvL wrote:
Fri Jul 19, 2019 4:53 am
have a look at the fcFEM source code
Where is the fcFEM source code?
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HarryvL
Posts: 1052
Joined: Sat Jan 06, 2018 7:38 pm

### Re: FEM-Hydrostatic pressure constraint help/request

Jee-Bee
Posts: 1966
Joined: Tue Jun 16, 2015 10:32 am
Location: Netherlands

### Re: FEM-Hydrostatic pressure constraint help/request

Edit to late
HarryvL
Posts: 1052
Joined: Sat Jan 06, 2018 7:38 pm

### Re: FEM-Hydrostatic pressure constraint help/request

HarryvL
Posts: 1052
Joined: Sat Jan 06, 2018 7:38 pm

### Re: FEM-Hydrostatic pressure constraint help/request

Jee-Bee wrote:
Fri Jul 19, 2019 4:38 pm
Edit to late
What do you mean @Jee-Bee?
Jee-Bee
Posts: 1966
Joined: Tue Jun 16, 2015 10:32 am
Location: Netherlands

### Re: FEM-Hydrostatic pressure constraint help/request

I saw the question of Kunda1
after i posted the answer i saw you were first... so i was to late
HarryvL
Posts: 1052
Joined: Sat Jan 06, 2018 7:38 pm

### Re: FEM-Hydrostatic pressure constraint help/request

Aha
Barry-h
Posts: 2
Joined: Sun Jul 21, 2019 11:28 am

### Re: FEM-Hydrostatic pressure constraint help/request

Hi,
I'm a new user of Freecad and FEM but came across this video and wondered if the same method could be applied in Freecad.