initial_state_function.h

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//
// SPDX-License-Identifier: Apache-2.0
// [LANL Copyright Statement]
// Copyright (C) 2023 - 2024 by the ryujin authors
// Copyright (C) 2023 - 2024 by Triad National Security, LLC
//
 
#pragma once
 
#include <initial_state_library.h>
 
#include <deal.II/base/function_parser.h>
 
namespace ryujin
{
  namespace ShallowWaterInitialStates
  {
    template <typename Description, int dim, typename Number>
    class Function : public InitialState<Description, dim, Number>
    {
    public:
      using HyperbolicSystem = typename Description::HyperbolicSystem;
      using View =
          typename Description::template HyperbolicSystemView<dim, Number>;
      using state_type = typename View::state_type;
 
      Function(const HyperbolicSystem &hyperbolic_system,
               const std::string subsection)
          : InitialState<Description, dim, Number>("function", subsection)
          , hyperbolic_system_(hyperbolic_system)
      {
 
        depth_expression_ = "1.4";
        this->add_parameter("water depth expression",
                            depth_expression_,
                            "A function expression describing the water depth");
 
        velocity_expression_ = "3.0";
        this->add_parameter("velocity expression",
                            velocity_expression_,
                            "A function expression describing the velocity");
 
        /*
         * Set up the muparser object with the final flux description from
         * the parameter file:
         */
        const auto set_up_muparser = [this] {
          using FP = dealii::FunctionParser<dim>;
          /*
           * This variant of the constructor initializes the function
           * parser with support for a time-dependent description involving
           * a variable »t«:
           */
          depth_function_ = std::make_unique<FP>(depth_expression_);
          velocity_function_ = std::make_unique<FP>(velocity_expression_);
        };
 
        set_up_muparser();
        this->parse_parameters_call_back.connect(set_up_muparser);
      }
 
      state_type compute(const dealii::Point<dim> &point, Number t) final
      {
        const auto view = hyperbolic_system_.template view<dim, Number>();
 
        dealii::Tensor<1, 2, Number> primitive;
 
        depth_function_->set_time(t);
        primitive[0] = depth_function_->value(point);
        velocity_function_->set_time(t);
        primitive[1] = velocity_function_->value(point);
 
        return view.from_initial_state(primitive);
      }
 
    private:
      const HyperbolicSystem &hyperbolic_system_;
 
      bool use_primitive_state_functions_;
 
      std::string depth_expression_;
      std::string velocity_expression_;
      std::string bathymetry_expression_;
 
      std::unique_ptr<dealii::FunctionParser<dim>> depth_function_;
      std::unique_ptr<dealii::FunctionParser<dim>> velocity_function_;
      std::unique_ptr<dealii::FunctionParser<dim>> bathymetry_function_;
    };
  } // namespace ShallowWaterInitialStates
} // namespace ryujin