[deal.II] Use of 'VectorTools::interpolate_boundary_values' using numerical solution.

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Hi, all ```
```

I am always thank you for all guys here in this community.

I have a question on the use of  VectorTools::interpolate_boundary_values
functions

Typically we use this function in when we set-up system as in the form

VectorTools::interpolate_boundary_values (dof_handler,

1,

*Original**_VelBndValues<dim>(),*

constraints,

fe.component_mask(velocities));

The red lined functions are usually declared out side of main class.

One problem I am interested in now is to (Part A) solve stokes flow with no
slip boundary condition on every boundary one time (as step-22), -

and then to (Part B) solve same system again with slightly different
boundary condition comes from the straight problem

If I finish Part A, i have numerical solution of (u,p) linked with dot
handler.

In (Part B), I post process solutions part A, e.g. I calculated stress
value and I calculated tangential velocity of a boundary using Navier slip
condition,

So, I need to use

VectorTools::interpolate_boundary_values (dof_handler,

1,

*New_VelBndValues<dim>(),*

constraints,

fe.component_mask(velocities));

such that

template<intdim>

double

New_VelBndValues<dim>::value (constPoint<dim>  &p,

constunsignedintcomponent) const

{

Assert (component < this->n_components,

ExcIndexRange (component, 0, this->n_components));

if(component == 0)

*return calc_tangential_velocity ();     (Error Here!!)*

else

return0;

}

where '*calc_tangential_velocity ();' *is declared in main class, since I
should have information of dot_handler and solution vectors.

template<intdim>

classStokesProblem

{

public:

StokesProblem (constunsignedintdegree);

voidrun ();

private:

……

*double calc_tangential_velocity ();*

BlockVector<double> solution;

};

////////

Obviously, this method does not work, I mean I cannot compile the code and
it shows  'use of undeclared identifier 'calc_tangential_velocity' on the
line  *(Error Here!!)*

I would appreciate any one who comment it. It seems that complier has to
know what is that before.

Will this be possible in a certain way? How can I  go around this problem ?

Thanks,

Jaekwang

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• [deal.II] Use of 'VectorTools::interpolate_boundary_values' u... Jaekwang Kim