Thank you very much Prof. Bangerth. The Neuman condition is now implemented
successfully on the face elements in relatively simpler way (which you
proposed for me). Now I have moved ahead to implement the flux BC on the
top edge of square plate and I am taking help of your tutorial step-26. But
in this code the structure is a bit different than the step-8 i.e. the
*cell_rhs
*looks like being formed now in *create_right_hand_side* function.
So my question is that can I simply use the heat source code of following
function:
*template<int dim> double RightHandSide<dim>::value (const Point<dim>
&p, const unsigned int component) const*
to select the points of top edge of the domain to declare the flux input or
Neuman BC (i.e. in other words moving source on top and source now putting
heat inside the domain) or there is other valid way for that? Thank you in
advance for your suggestion!
On Thursday, April 4, 2019 at 3:10:35 PM UTC+2, Wolfgang Bangerth wrote:
>
> On 4/4/19 4:05 AM, Muhammad Mashhood wrote:
> >
> > 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).
>
> The way you do things here does not work. You are assembling boundary
> terms on
> an individual face here. You need to evaluate the rhs_values *for this
> particular face*. In other words, you need to call the function you showed
> us with
> fe_face_values.get_quadrature_points()
> (not fe_values.get_quadrature_points()), and not with an iterator to the
> cell
> but with an iterator to the face.
>
> This way, you do not need the function you showed us guess whether a
> quadrature point is near a particular boundary -- the function already
> *knows*
> that the quadrature points lie on that boundary, because it is only called
> for
> such points.
>
> Best
> W.
>
>
> --
> ------------------------------------------------------------------------
> Wolfgang Bangerth email: bang...@colostate.edu
> <javascript:>
> www: http://www.math.colostate.edu/~bangerth/
>
>
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