Jane,
I'm wondering whether I've misunderstood how to use the FunctionMap
> declaration. I'm needing it to use for
> VectorTools::compute_nonzero_normal_flux_constraints
>
> At the moment I am trying to apply nonzero normal component of the normal
> stress in step-22 on a boundary id that is 2
>
> I have tried
>
> std::set<types::boundary_id> bottom_normal_flux_boundaries;
>
> bottom_normal_flux_boundaries.insert (2);
>
> typename FunctionMap<dim>::type bottom_normal_map;
>
> RockBottomValues<dim> bottom_nonzero_normal_stress;
>
> bottom_normal_map[0] = &bottom_nonzero_normal_stress;
>
> VectorTools::compute_nonzero_normal_flux_constraints
> (dof_handler, 0,
>
>
> bottom_normal_flux_boundaries,
>
>
> bottom_normal_map,
>
>
> constraints);
>
>
> with my nonzero function as
>
>
> template <int dim>
>
> class RockBottomValues : public Function<dim>
>
> {
>
> public:
>
> RockBottomValues () : Function<dim>(1) {}
>
>
>
> virtual double value (const Point<dim> &p,
>
> const unsigned int component = 0) const;
>
> };
>
>
> template <int dim>
>
> double RockBottomValues<dim>::value (const Point<dim> &p,
>
> const unsigned int
> /*component*/) const
>
> {
>
> return -10.0+p[1];
>
> }
>
>
>
> I'm not sure if I understand what I am doing when i write,
> bottom_normal_map[0] = &bottom_nonzero_normal_stress;
>
> I original had bottom_normal_map[2] = &bottom_nonzero_normal_stress;
>
>
> as i thought it was to do with the boundary indicator.
>
Yes, it clearly does. Just as the documentation
<https://www.dealii.org/8.5.1/doxygen/deal.II/structFunctionMap.html> says,
this is std::map is supposed to describe which Function object to use for
which boundary_id.
>
>
> The first gave me a segmentation fault error, something to do with memory
> i'm guessing, and the second gave me a dimension mismatch error, even
> though my normal component would just be a scalar value.
>
The documentation
<https://www.dealii.org/8.5.1/doxygen/deal.II/group__constraints.html#ga5b13c2da1b235c86cdbce2270525db99>
uses the vector-valued u_\Gamma for describing what the function does and
in fact we are expecting the FunctionMap to point to such a vector-valued
Function, i.e. it should have spacedim components.
In the end, this means that you have to provide u_\Gamma instead of u_\Gamm
\cdot n.
Best,
Daniel
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