Re: [deal.II] Using interpolate_boundary_conditions

[Amy Kaczmarowski]

Perfect!  Thank you this was exactly what I was missing.

Amy


On Tuesday, October 1, 2019 at 3:18:20 PM UTC-6, Wolfgang Bangerth wrote:
>
>
> Amy, 
>
> > template  
> > class BoundaryValuesU : public Function{ 
> >public: 
>
> You are correct: You need to tell the base class how many vector 
> components 
> your function has. You should be able to do this by adding a constructor: 
>
>BoundaryValuesU () 
>  :  Function (dim)// your function has 'dim' components 
>{} 
>
>
> >  virtual void vector_value(const Point & p, Vector 
> ) 
> > const override 
> >{ 
> >  double xpos, ypos, zpos; 
> >  xpos = p[0]; 
> >  ypos = p[1]; 
> >  if (dim==3){zpos=p[2];} 
> >  else {zpos=0.0;} 
> >  values[0] 
> > 
> = 
> xpos/std::pow(std::pow(xpos,2.0)+std::pow(ypos,2.0)+std::pow(zpos,2.0),0.5)*0.1;
>  
>
> >  values[1] 
> > 
> = 
> ypos/std::pow(std::pow(xpos,2.0)+std::pow(ypos,2.0)+std::pow(zpos,2.0),0.5)*0.1;
>  
>
> >  values[2] 
> > 
> = 
> zpos/std::pow(std::pow(xpos,2.0)+std::pow(ypos,2.0)+std::pow(zpos,2.0),0.5)*0.1;
>  
>
> >  return; 
> >  } 
>
> You can write this much simpler using the fact that Point objects are 
> really 
> just vectors: 
>
>virtual void vector_value (...) const override 
>{ 
>   Tensor<1,dim> displacement = 0.1 * p / p.norm(); 
>   for (unsigned int d=0; d values[d] = displacement[d]; 
>} 
>
> Best 
>   W. 
>
> -- 
>  
> Wolfgang Bangerth  email: bang...@colostate.edu 
>  
> www: http://www.math.colostate.edu/~bangerth/ 
>
>

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[deal.II] Using interpolate_boundary_conditions

[Amy Kaczmarowski]

Hi,

I'm attempting to apply a displacement boundary condition on a surface in 
my problem.  However, I would like the direction of the displacement of 
each point on the surface to depend on its direction from some point (for 
example the origin).  Imagine a balloon inflating where the displacement 
direction is from the center of the balloon.  My thought was to use a 
function similar to the example boundary conditions in step 23 but extended 
for 3 dimensions.  I defined the following class in my code:

template 
class BoundaryValuesU : public Function{
  public:
virtual void vector_value(const Point & p, Vector ) 
const override
  {
double xpos, ypos, zpos;
xpos = p[0];
ypos = p[1];
if (dim==3){zpos=p[2];}
else {zpos=0.0;}
values[0] 
= 
xpos/std::pow(std::pow(xpos,2.0)+std::pow(ypos,2.0)+std::pow(zpos,2.0),0.5)*0.1;
values[1] 
= 
ypos/std::pow(std::pow(xpos,2.0)+std::pow(ypos,2.0)+std::pow(zpos,2.0),0.5)*0.1;
values[2] 
= 
zpos/std::pow(std::pow(xpos,2.0)+std::pow(ypos,2.0)+std::pow(zpos,2.0),0.5)*0.1;
return; 
}
  };

Then I apply the boundary conditions in the following way to the surface 
with boundary id 2:

std::vector uBC (3, true);
BoundaryValuesU boundary_values_u_function;
VectorTools::interpolate_boundary_values (dof_handler, 2, 
boundary_values_u_function, constraints, uBC);

However, when I attempt to run with this case I get the following error:

An error occurred in line <2263> of file 

 
in function
void 
dealii::VectorToolsdo_interpolate_boundary_values(const 
M_or_MC &, const DoFHandlerType &, const 
std::map *, 
std::less, std::allocator *>>> &, std::map, std::allocator>> &, const dealii::ComponentMask &) [with dim = 3, spacedim = 
3, number = double, DoFHandlerType = dealii::DoFHandler, M_or_MC = 
dealii::Mapping]
The violated condition was:
n_components == i->second->n_components
Additional information:
Dimension 3 not equal to 1.

Is there a way I am supposed to be initializing n_components in the class 
to make this work?  Or is this just the wrong way to be doing this?

Thank you.

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