set pressure for boundary

[saxonfahrer]

Hello,
i try to make a linear elasticity FEM with elmer. In the model i have a cube with a fancy shaped hole inside. I want to apply pressure to the inner walls of the hole.
But for "boundary conditions" there is no item "pressure" in the linear elasticity section. Pressure is only applyable via "body forces".

Is there a way to told elmer, that i want to apply pressure to a surface (boundary)?

Thanks,

saxonfahrer

[raback]

Hi, try with "Normal Force"

[saxonfahrer]

I tried this, but then i have to know the area of the surface, or?
Unfortunatly (for me) this is tricky to determine. Or can i put the pressure value to "normal force"?

Additionally: what is the natural lenght scale in emler: mm or m? So if i import a model/mesh from gmsh (and there are only numbers), did elmer interpret this as millimeters or meters?

[raback]

Hi

The unit of "Normal Force" is the same as the unit of pressure (pressure as a keyword is related to Navier-Stokes equation). There is basically no preferred unit system in Elmer as long as it's consistant. SI units is usally a safe choice.

-Peter

[mzenker]

Hi,

I may add that, if you have problems with the length units, you could have a look at this thread: viewtopic.php?f=4&t=364&p=2879

HTH,

Matthias

[saxonfahrer]

Thanks, this really helped my!!

Best regards,
saxonfahrer

[mzenker]

Hi Elmer team,

since this is a FAQ, I would suggest to add a paragraph about units and coordinate scaling to the ElmerSolver manual - even though an item about units figures already in the FAQ on the wiki, as I just discovered...

Matthias

[hazelsct]

Hi, it sounds like "Normal Force" should be "Normal Traction" which is force per unit area. Would you like a patch for this?