Re: impose a non constant stress normal to a surface

[Konstantinos Poulios]

Dear Anne Cecile

To be more accurate, you impose a traction on a surface. What you mean with "pressure" must be traction normal to the surface. For small deformations the _expression_ is very simple:

md.add_linear_term(mim, "-pressure*Normal.Test_u", BOUNDARY_REGION)

where pressure can be a constant, or a field defined (as data) on a mesh_fem, or a field defined (as data) on a mesh_im_data structure, or some GWFL _expression_.

For example, with

md.add_linear_term(mim, "(water_level-water_density*g*X(2))*Normal.Test_u", BOUNDARY_REGION)

you would apply a depth-dependent traction acting on a submerged object in water.

For large deformations, the formulas are more complex and the term nonlinear, but apart from that, it is as easy to implement in GetFEM.

BR

Kostas

P.S. I am only in doubt about the sign of the overall _expression_, but you can try both possibilities with + and - and see which fits you.

On Thu, Mar 24, 2022 at 5:47 PM Lesage,Anne Cecile J <AJLesage@mdanderson.org> wrote:

Dear all

 

I would like to impose an hydrostatic pressure on a mesh surface

I think it is like impose a non constant stress normal to that surface, right?

How shall I do that in a python script?

 

Thank you

Regards

Anne-Cecile

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