initial_state_three_state_contrast.h

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//
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// Copyright (C) 2023 - 2025 by the ryujin authors
//
 
#pragma once
 
#include <compile_time_options.h>
 
#include <initial_state_library.h>
 
namespace ryujin
{
  namespace EulerInitialStates
  {
    template <typename Description, int dim, typename Number>
    class ThreeStateContrast : public InitialState<Description, dim, Number>
    {
    public:
      using HyperbolicSystem = typename Description::HyperbolicSystem;
      using View = typename HyperbolicSystem::template View<dim, Number>;
      using state_type = typename View::state_type;
      using state_type_1d =
          typename HyperbolicSystem::template View<1, Number>::state_type;
 
      ThreeStateContrast(const HyperbolicSystem &hyperbolic_system,
                         const std::string &subsection)
          : InitialState<Description, dim, Number>("three state contrast",
                                                   subsection)
          , hyperbolic_system_(hyperbolic_system)
      {
 
        primitive_left_[0] = 1.;
        primitive_left_[1] = 0.;
        if constexpr (View::have_energy_equation)
          primitive_left_[2] = 1.e3;
        this->add_parameter("primitive state left",
                            primitive_left_,
                            "1d primitive state [rho, u, p] on the left (or "
                            "[rho, u] for the barotropic Euler module)");
 
        left_length_ = 0.1;
        this->add_parameter("left region length",
                            left_length_,
                            "The length of the left region");
 
        primitive_middle_[0] = 1.;
        primitive_middle_[1] = 0.;
        if constexpr (View::have_energy_equation)
          primitive_middle_[2] = 1.e-2;
        this->add_parameter("primitive state middle",
                            primitive_middle_,
                            "1d primitive state [rho, u, p] in the middle (or "
                            "[rho, u] for the barotropic Euler module)");
 
        middle_length_ = 0.8;
        this->add_parameter("middle region length",
                            middle_length_,
                            "The length of the middle region");
 
        primitive_right_[0] = 1.;
        primitive_right_[1] = 0.;
        if constexpr (View::have_energy_equation)
          primitive_right_[2] = 1.e2;
        this->add_parameter("primitive state right",
                            primitive_right_,
                            "1d primitive state [rho, u, p] on the right (or "
                            "[rho, u] for the barotropic Euler module)");
 
        const auto convert_states = [&]() {
          const auto view = hyperbolic_system_.template view<dim, Number>();
          state_left_ = view.from_initial_state(primitive_left_);
          state_middle_ = view.from_initial_state(primitive_middle_);
          state_right_ = view.from_initial_state(primitive_right_);
        };
        this->parse_parameters_call_back.connect(convert_states);
        convert_states();
      }
 
      state_type compute(const dealii::Point<dim> &point, Number /*t*/) final
      {
        return point[0] >= left_length_ + middle_length_ ? state_right_
               : point[0] >= left_length_                ? state_middle_
                                                         : state_left_;
      }
 
    private:
      const HyperbolicSystem &hyperbolic_system_;
 
      Number left_length_;
      Number middle_length_;
 
      state_type_1d primitive_left_;
      state_type_1d primitive_middle_;
      state_type_1d primitive_right_;
 
      state_type state_left_;
      state_type state_middle_;
      state_type state_right_;
    };
  } // namespace EulerInitialStates
} // namespace ryujin