You need to give the whole "previous_solution" to interpolate(), not
an individual block. You can use the component_mask argument to only
interpolate on some components of your solution (x velocity for
example).
On Mon, Dec 19, 2016 at 2:02 PM, Jaekwang Kim <jaekwan...@gmail.com> wrote:
> Hi all.
>
> I have a question on the solution initialization for iterative methods, in
> vector valued problem.
>
> For example, I want to solve 2D flow, where my solution consist of two
> block, one is for velocities and the other is for pressure.
>
> First, I construct my initial solution as below
>
>
>
> -Declaration
>
>
> ...BlockVector<double> previous_solution;
>
> .......
>
>
> -Block build
>
>
> {
>
> BlockDynamicSparsityPattern dsp (2,2);
>
>
> dsp.block(0,0).reinit (n_u, n_u);
>
> dsp.block(1,0).reinit (n_p, n_u);
>
> dsp.block(0,1).reinit (n_u, n_p);
>
> dsp.block(1,1).reinit (n_p, n_p);
>
>
> dsp.collect_sizes();
>
>
> DoFTools::make_sparsity_pattern (dof_handler, dsp, constraints,
> false);
>
> sparsity_pattern.copy_from (dsp);
>
> }
>
>
> -reinitialization
>
>
> previous_solution.reinit (2);
>
> previous_solution.block(0).reinit (n_u);
>
> previous_solution.block(1).reinit (n_p);
>
> previous_solution.collect_sizes ();
>
>
>
>
> After that , I wanted to set my x-componet of velocities by following
> command lines.
>
>
>
> VectorTools::interpolate(dof_handler,initialize_solution<dim>(),previous_solution.block(0));
>
>
>
> However this function does not work because my dof_handler has more degree
> of freedom. (Degree of freedom of all velocities components + pressure
> components)
>
> So I met error message which says
>
>
>
> The violated condition was:
>
> vec.size() == dof.n_dofs()
>
> The name and call sequence of the exception was:
>
> ExcDimensionMismatch (vec.size(), dof.n_dofs())
>
> Additional Information:
>
> Dimension 162 not equal to 187
>
>
>
>
> It seems that I have to extract dofs that are only for velocity component to
> initialize my u_x velocities.
>
> Is there any way to do this?
>
> Or is there any other way to initialize my particular solution components
> only....?
>
>
> &&FYI initialize_solution<dim> function looks like as follow.
>
>
> template <int dim>
>
> class initialize_solution : public Function<dim>
>
> {
>
> public:
>
>
>
> initialize_solution () : Function<dim>() {}
>
>
>
> virtual double value (const Point<dim> &p,
>
> const unsigned int component = 0) const;
>
>
>
> };
>
>
>
>
>
> template <int dim>
>
> double
>
> initialize_solution<dim>::value (const Point<dim> &p,
>
> const unsigned int component) const
>
> {
>
> Assert (component < this->n_components,
>
> ExcIndexRange (component, 0, this->n_components));
>
>
>
> double x=p[0];
>
> double y=p[1];
>
> double height = 1e-3; // unit of [m]
>
> double return_value;
>
>
>
> return_value=std::sin(y*Pi/height);
>
>
>
> if (component == 0) // impose only in x direction
>
> return return_value;
>
> else
>
> return 0;
>
>
>
> }
>
>
>
>
> --
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--
Timo Heister
http://www.math.clemson.edu/~heister/
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