Re: [Getfem-users] (no subject)

[Yves Renard]

Dear Yuri,

There is of course no problem to transcribe your problem into the assembly language of Getfem. You can mixt domain and boundary terms with no problem.
Just a question on the _expression_ you give : some polynomials are placed outside the integrals. Is it normal and if yes, what is the sense of this.

Depending if you use the Matlab or Python or Scilab interface or if you write directly your code in C++, you can find some examples helping you to create the framework of your code in the test directories of Getfem (see http://getfem.org/tutorial/index.html)

For instance, what you denote the "implicit boundary term" can be coded by an assembly string of the following form
"([P5(X[1],X(2]), P6(X[1],X[2]).Grad_u + l*u)*Test_lambda - lambda*Test_u"
where 'u' and 'lambda' are the unknowns and P5, P6 functions should be defined first (if you have an explicit _expression_, you can just plug it here), and 'l' is a data that should be declared.

Regards,

Yves.


Le 10/10/2017 à 20:02, Юрий Кульчицкий a écrit :

Dear Getfem users,

I am experiencing an issue related to the problem formulation in the case when there are both boundary integrals and usual integrals in the 2D case.

A boundary integral arises both from adding an implicit boundary condition using an augmented Lagrange formulation and from the basic weak form equation. It also implies an additional unknown (which is a corresponding multiplier) and an additional test function.

May you point to me a way how can I formulate the problem correctly? I would be very grateful for any help. I tried to understand how bricks work, but so far with no success related to different integration domains.

I also enclose the full (simplified) weak form as png image if it would help: https://image.ibb.co/jTwUDw/La_Te_X_Example.png.

Sorry if this question is too simple. I'm not quite familiar with the library and the inner details of its FEM realization yet.

Regards,

Yuri Kulchitsky

-- 

  Yves Renard (address@hidden)       tel : (33) 04.72.43.87.08
  Pole de Mathematiques, INSA-Lyon             fax : (33) 04.72.43.85.29
  20, rue Albert Einstein
  69621 Villeurbanne Cedex, FRANCE
  http://math.univ-lyon1.fr/~renard

---------