Re: [Getfem-users] Example of a simple mixed-problem, or problem with two variables

[Jehanzeb Hameed]

Thanks! I think I know how to go about this now.

On Mon, Jul 6, 2009 at 10:36 AM, Yves Renard<address@hidden> wrote:
>
> Dear Jehanzeb,
>
> Ok, I just believed you use the Matlab interface. For C++ programs, you can
> view a huge number of examples of assembly procedures in the file
> src/getfem/getfem_assembling.h including some mixed terms (such as
> asm_stokes_B(...) for the Stokes problem). You should use the
> generic_assembly object (see Getfem documentation).
>
> Yves.
>
> On lundi 6 juillet 2009, Jehanzeb Hameed wrote:
>> Dear Renard,
>>
>> I cant seem to find the function "gf_asm" to use in C++ code. I see it
>> in a .cc file in the source code for getfem, but there seems to be no
>> prototype for it in a header file.
>>
>> Do you mean that I should use getfem::generic_assembly in the way you
>> have described?
>>
>> Thanks,
>> -Jehanzeb
>>
>> On Sun, Jul 5, 2009 at 3:39 PM, Renard Yves<address@hidden> wrote:
>> > Dear Jehanzeb,
>> >
>> > You have to use a volumic assembly . An example  for the matrix of the
>> > Laplace operator is
>> >
>> > gf_asm('volumic',['a=data(#2); ',...
>> >       'M(#1,#1)+=sym(comp(Grad(#1).Grad(#1).Base(#2))(:,i,:,i,j).a(j))'],
>> > mim, mf, mf_data, A);
>> >
>> > A matrix for a mixed term can be obtained in a same way with two mf :
>> >
>> >  gf_asm('volumic', 'M(#1,#1)+=comp(Grad(#1).Base(#2))(:,i,i,:)', mim,
>> > mf1, mf2);
>> >
>> > where mf1 should be a vectorial fem (for more details see the Getfem++
>> > documentation).
>> >
>> > Yves.
>> >
>> > Jehanzeb Hameed <address@hidden> a écrit :
>> >> I had a look at the Stokes example. It uses model bricks to form the
>> >> system. From the documentation, it seems using model bricks implicitly
>> >> chooses the bilinear variational form. I would like to define my own
>> >> bilinear form to form the matrix, in which I can define terms like
>> >> div(q) + c u  (q = vector, c = constant, u = another variable besides
>> >> q). How would I go about this?
>> >>
>> >> Thanks,
>> >> -Jehanzeb
>> >>
>> >> On Sun, Jul 5, 2009 at 11:05 AM, Iago Barbeiro<address@hidden>
>> >>
>> >> wrote:
>> >>> Dear Jehanzeb,
>> >>>
>> >>> I think you may start by looking the Stokes example.
>> >>> It deals with two variables (û=uî+v^j and p) and has the term
>> >>> div(û).dp. Bon courage!
>> >>>
>> >>> Iago
>> >>>
>> >>> On Sun, Jul 5, 2009 at 6:07 AM, Jehanzeb Hameed <address@hidden>
>> >>>
>> >>> wrote:
>> >>>> Hello,
>> >>>>
>> >>>> Is there a simple example in getfem where assembly is for two
>> >>>> variables? E.g. we may want to solve for "u" and "q" (with an equation
>> >>>> defining the relationship between u and q) . Such a case arises in
>> >>>> mixed methods.  Is there an example for mixed-poisson problem
>> >>>> somewhere? I know mixed-elasticity problem is given with getfem, but I
>> >>>> am not familiar with that particular problem.
>> >>>>
>> >>>> In particular, I am not sure how to refer to "q" and "u" in
>> >>>> generic_assembly routines. Say my weak form involves div(q) . v ? How
>> >>>> will I write this in "assem.set" routine? (I am guessing thats what I
>> >>>> am supposed to do).
>> >>>>
>> >>>> Thanks,
>> >>>> -Jehanzeb
>> >>>>
>> >>>> _______________________________________________
>> >>>> Getfem-users mailing list
>> >>>> address@hidden
>> >>>> https://mail.gna.org/listinfo/getfem-users
>> >>
>> >> _______________________________________________
>> >> Getfem-users mailing list
>> >> address@hidden
>> >> https://mail.gna.org/listinfo/getfem-users
>
>
>
> --
>
>  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
>
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>