Thank you Prof. Bangerth for your quick concern. I am on basic level for
FEM code programming especially deal.ii and also quite only a bit familiar
with object oriented programming in C++.
Sorry if my question was not clear, let me explain it a bit:
Actually, I am trying to follow the tutorial step-8 for extending it to
applying BC upon the labelled edges during meshing in mesh generator. I am
quit successful in applying Dirchlet (displacement) BC simply using
function "interpolate_boundary_values()". Now it is time to apply Neumann
(force) BC.
For this yes you guessed right that I am using "FEFaceValues" in following
code as per tutorials:
for (unsigned int f=0; f<GeometryInfo<dim> :: faces_per_cell; ++f)
if (cell->face(f)->at_boundary() )
{
fe_face_values.reinit (cell,f);
for (unsigned int i=0; i<dofs_per_cell; ++i)
{
const unsigned int
component_i = fe.system_to_component_index(i).first;
for (unsigned int q_point=0; q_point<n_face_q_points;
++q_point)
cell_rhs(i) += fe_face_values.shape_value(i,q_point) *
rhs_values[q_point][component_i] *
fe_face_values.JxW(q_point);
}
}
Where the *"rhs_values"* are being extracted from my previously mentioned
function "*right_hand_side (fe_values.get_quadrature_points(), rhs_values,
cell);"* in a same loop of "*for (; cell!=endc; ++cell)" *and the code for
this "*right_hand_side" *function is that which I mentioned previously.
In my limited knowledge I am going through each face in cell as in 2D there
are four edges are present and I want to choose the edge number 3 (which is
upper outer edge in my example case).
*So the problem is how to tell program that which quadrature point is near
the concerned boundary edge e.g. edge no. 3 so that the force boundary
value can be applied? *
You can also suggest and make comment in your expert opinion if the idea or
my methodology is wrong or needs modification. Thank you in advance for
your concern and expert opinion.
On Wednesday, April 3, 2019 at 5:03:06 PM UTC+2, Wolfgang Bangerth wrote:
>
> On 4/3/19 8:04 AM, Muhammad Mashhood wrote:
> >
> > I am trying to apply the Neumann
> (force)
> > BC on the edge using the right_hand_side() function which I modified as
> following:
> >
> >
> > void right_hand_side (const std::vector<Point<dim> > &points, // the
> active
> > cell is also imported when right hand side is called to induce some
> Neumann BC
> > std::vector<Tensor<1, dim> > &values,
> > typename DoFHandler<dim>::active_cell_iterator
> &
> > cell_in_rhs)
> >
> > for (unsigned int f=0; f < GeometryInfo<dim> :: faces_per_cell; ++f)
> > {
> > if (cell_in_rhs->face(f)->at_boundary() &&
> > cell_in_rhs->face(f)->boundary_id() == 3)
> > {
> > std::cout << "points.size(): "<<
> points.size()<<"
> > :"<<std::endl;
> > values[0][1] = 2.0;
> > values[2][1] = 2.0;
> >
> > }
> > }
> >
>
> I don't think I understand this code. The Neumann boundary conditions only
> appear in *boundary* integrals. How are you using the function you have
> here?
> For integrals over cells (using FEValues) or integrals over faces
> (FEFaceValues)? If it is the latter, you are integrating over *one
> specific
> face* of the current cell, so it makes no sense to loop over all faces
> *within
> this function*.
>
> Best
> W.
>
> --
> ------------------------------------------------------------------------
> Wolfgang Bangerth email: [email protected]
> <javascript:>
> www: http://www.math.colostate.edu/~bangerth/
>
>
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