Thank you, Wolfgang, for your reply.
Now I understand.
Is there a built-in function to apply a velocity field which points in the
direction normal to the boundary?
Or I could implement a modified version of the
compute_nonzero_normal_flux_constraints function that does that
Kind regards,
Giovanna
On Wednesday, October 6, 2021 at 8:57:53 PM UTC-7 Wolfgang Bangerth wrote:
>
> > I ran a test with a circular hole and a square hole. In both case I
> didn't get
> > what I expected (see images attached).
> >
> > Eventually, I need to solve the problem on an irregular inner boundary
> so I am
> > looking for a robust method.
> >
> > I copied below the code. I very much appreciate any help with this.
> >
> > Thank you
> > Giovanna
> >
> > - - - - - - - - - -
> > std::set<types::boundary_id> normal_flux_boundaries;
> > std::map<types::boundary_id, const Function<dim> *> boundary_functions;
> > double velocity = 0.005;
> > Functions::ConstantFunction<dim, double>
> > constant_velocity(velocity,numVariables);
>
> This corresponds to a vector-valued function equal to
> V = (v,v,...,v) // every component is equal to 'velocity'
>
>
> > normal_flux_boundaries.insert (Internal_boundary);
> > boundary_functions.insert({Internal_boundary, &constant_velocity});
> >
> > VectorTools::compute_nonzero_normal_flux_constraints ( dof_handler,
> > 0, //
> > first_vector_component,
> > normal_flux_boundaries,
> > boundary_functions,
> > constraints,
> > StaticMappingQ1< dim >::mapping
> > );
>
> And this function then computes the constraints that correspond to
> ensuring
> that the solution's normal component equals
> n * V
> Because V points diagonally to the top right in your figures, the
> constraint
> is that the normal component is zero whenever 'n' points to the top left
> or
> bottom right, which is exactly what you see in the picture of your square
> with
> a circular hole. In other words, I think it all looks like it should given
> what the function is doing :-)
>
> Best
> W.
>
> --
> ------------------------------------------------------------------------
> Wolfgang Bangerth email: [email protected]
> www: http://www.math.colostate.edu/~bangerth/
>
>
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