mapping_deformation_function.h

/*  ______________________________________________________________________
 *
 *  ExaDG - High-Order Discontinuous Galerkin for the Exa-Scale
 *
 *  Copyright (C) 2021 by the ExaDG authors
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
 *  ______________________________________________________________________
 */
 
#ifndef INCLUDE_GRID_MAPPING_DEFORMATION_FUNCTION_H_
#define INCLUDE_GRID_MAPPING_DEFORMATION_FUNCTION_H_
 
#include <exadg/grid/grid_data.h>
#include <exadg/grid/mapping_deformation_base.h>
 
namespace ExaDG
{
template<int dim, typename Number>
class DeformedMappingFunction : public DeformedMappingBase<dim, Number>
{
public:
  typedef dealii::LinearAlgebra::distributed::Vector<Number> VectorType;
 
  DeformedMappingFunction(std::shared_ptr<dealii::Mapping<dim> const>  mapping_undeformed,
                          unsigned int const                           mapping_degree_q_cache,
                          dealii::Triangulation<dim> const &           triangulation,
                          std::shared_ptr<dealii::Function<dim>> const mesh_deformation_function,
                          double const                                 start_time)
    : DeformedMappingBase<dim, Number>(mapping_undeformed, mapping_degree_q_cache, triangulation),
      mesh_deformation_function(mesh_deformation_function),
      triangulation(triangulation)
  {
    update(start_time, false, dealii::numbers::invalid_unsigned_int);
  }
 
  void
  update(double const     time,
         bool const       print_solver_info,
         types::time_step time_step_number) override
  {
    (void)print_solver_info;
    (void)time_step_number;
 
    mesh_deformation_function->set_time(time);
 
    this->do_initialize(triangulation, mesh_deformation_function);
  }
 
private:
  void
  do_initialize(dealii::Triangulation<dim> const &     triangulation,
                std::shared_ptr<dealii::Function<dim>> displacement_function)
  {
    AssertThrow(dealii::MultithreadInfo::n_threads() == 1, dealii::ExcNotImplemented());
 
    AssertThrow(get_element_type(triangulation) == ElementType::Hypercube,
                dealii::ExcMessage("Only implemented for hypercube elements."));
 
    // dummy FE for compatibility with interface of dealii::FEValues
    dealii::FE_Nothing<dim> dummy_fe;
    dealii::FEValues<dim>   fe_values(*this->mapping_undeformed,
                                    dummy_fe,
                                    dealii::QGaussLobatto<dim>(this->mapping_q_cache->get_degree() +
                                                               1),
                                    dealii::update_quadrature_points);
 
    this->mapping_q_cache->initialize(
      triangulation,
      [&](typename dealii::Triangulation<dim>::cell_iterator const & cell)
        -> std::vector<dealii::Point<dim>> {
        fe_values.reinit(cell);
 
        // compute displacement and add to original position
        std::vector<dealii::Point<dim>> points_moved(fe_values.n_quadrature_points);
        for(unsigned int i = 0; i < fe_values.n_quadrature_points; ++i)
        {
          // need to adjust for hierarchic numbering of dealii::MappingQCache
          dealii::Point<dim> const point =
            fe_values.quadrature_point(this->hierarchic_to_lexicographic_numbering[i]);
          dealii::Point<dim> displacement;
          for(unsigned int d = 0; d < dim; ++d)
            displacement[d] = displacement_function->value(point, d);
 
          points_moved[i] = point + displacement;
        }
 
        return points_moved;
      });
  }
 
  std::shared_ptr<dealii::Function<dim>> mesh_deformation_function;
 
  dealii::Triangulation<dim> const & triangulation;
};
 
} // namespace ExaDG
 
#endif /*INCLUDE_GRID_MAPPING_DEFORMATION_FUNCTION_H_*/