Dear Wolfgang,
This was easier than I thought. I followed your suggestion and used
VectorTools::interpolate
Final solution to set the values of the DOF using a parsed function:
// initialConditionParameters.uvw is my parsed function
// newtonUpdate is my local vector that I use to alter the DOF values
const FEValuesExtractors::Vector velocities (0);
const FEValuesExtractors::Scalar pressure (dim);
const MappingQ<dim> mapping (degreeVelocity_,femParameters.qmapping_all);
VectorTools::interpolate(mapping,
dof_handler,
initialConditionParameters.uvw,
newton_update,
fe.component_mask(velocities));
Thank you very much for the help!
On Thursday, 25 April 2019 09:32:09 UTC-4, Wolfgang Bangerth wrote:
>
> On 4/25/19 6:58 AM, Bruno Blais wrote:
> > I would like to be able to set-up an initial condition by fixing the
> value of
> > the DOF themselves by using their x,y(,z) position with a ParsedFuction.
> >
> > Generally, I set the initial condition by using an L2 projection of the
> > function (for complex function and higher order element I know this is
> more
> > appropriate).
> > However, for some stuff I would like to be able to fix the value of the
> DOF
> > directly.
> > My issue is, through the doxygen, I have not found a way to loop through
> the
> > DOF and to extract their position, even more when I have high order
> element or
> > when I have a multiplicity (say velocity-vector + pressure).
> >
> > What I would be looking into doing would be something similar to :
> >
> > loop over local DOF;
> > get DOF position
> > get DOF component (u[0], u[1], u[2], p)
> > calculate parsed function using the point
> > set the value of the DOF
> > end
> >
> > Is it something that is possible? This is a weird way of iterating since
> I
> > know we always loop over the cells. Maybe there is a way to achieve this
> by
> > looping over the cells and then looping over the DOF of the cells? This
> would
> > be slightly redundant, but I do not care since I am doing this only
> once.
>
> You can get the locations of DoFs using
> DoFTools::map_dofs_to_support_points().
>
> But maybe the easier way is to use
> VectorTools::interpolate_boundary_values()
> or project() and just pass it a function object that describes the
> function
> you want to set in terms of (x,y,z). This could be your ParsedFunction.
> interpolate_b_v() will then call your parsed function with a bunch of
> points
> that happen to correspond to the DoF locations, but it makes the
> connection
> internally and you no longer need to worry about which DoF sits where.
>
> Best
> W.
>
>
> --
> ------------------------------------------------------------------------
> Wolfgang Bangerth email: [email protected]
> <javascript:>
> www: http://www.math.colostate.edu/~bangerth/
>
>
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