Dear Prof. Wolfgang Bangerth,
I would like to thank you very much.
I am reading through the FE_NedelecSZ codes in Deal.II library.
I currently try to solve the electromagnetics problem, followed by the
research of Ross Kynch.
My goal is to compute the right hand side for the problem:
curl curl E + i*omega*mu*sigma*E = - Js
I only want to set the Js term here to be none zero, for example to be 1,
at a given degree of freedom (i.e. at source position), and 0 everywhere
else.
Thus, I need to write the codes to query if a degree of freedom is at
source position.
As you mentioned, now I think that I need to check if the source point is
on an edge when assembling the right hand side vector.
Could you please tell me help me about this?
Best regards,
Pham Ngoc Kien
Vào Th 3, 19 thg 2, 2019 vào lúc 15:45 Wolfgang Bangerth <
bange...@colostate.edu> đã viết:
> On 2/18/19 10:47 PM, Phạm Ngọc Kiên wrote:
> >
> > 2. I have tried some thing with the third method. And here-below is my
> code:
> >
> > Point<dim> p{0.5,0.5,0.5};//position in reference cell
> > Quadrature<dim> q(p);
> > FEValues<dim> fe_values_q(fe, q,update_quadrature_points);
> > fe_values_q.reinit(cell);
> >
> > //position in the real cell
> > std::vector<Point<dim>> dof_pos = fe_values_q.get_quadrature_points();
> > for (int k =0; k <dof_pos.size() ; ++k) {
> > for (int j =0; j <dim ; ++j) {
> > std::cout<<dof_pos[k][j];
> > std::cout<<"\n";
> > }
> > }
> >
> > From this codes, I can get the real position of arbitrary points in my
> current reference cell.
> >
> > However, my purpose is to get the real position of a given degree of
> freedom.
> >
> > Could you please tell me how to get the position of a degree of freedom
> in the reference cell?
>
> The problem is that the NedelecSZ element does not have any such position.
> You
> are thinking of Lagrange elements (or the regular Nedelec elements) for
> which
> every shape function has a specific location where it is defined: It is
> one
> there, and zero at all other such locations. This is what we call "support
> points" in deal.II.
>
> But the NedelecSZ element is not defined this way (at least that's what I
> believe to be the case). Rather, shape functions are defined in such a way
> that certain *integrals* (rather than *point values*) are zero or one for
> all
> shape functions. As a consequence, there are no support points: Shape
> functions (and degrees of freedom) are not defined at individual points,
> but
> at whole edges.
>
> This means that your approach can not work. I don't know what you want to
> do,
> but let's start with that: What is your *goal*? Maybe then we can think
> about
> how to achieve it!
>
> Best
> W.
>
> --
> ------------------------------------------------------------------------
> Wolfgang Bangerth email: bange...@colostate.edu
> www: http://www.math.colostate.edu/~bangerth/
>
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