flux_kpp.h

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//
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// Copyright (C) 2023 - 2026 by the ryujin authors
//
 
#pragma once
 
#include <ryujin/base/compile_time_options.h>
#include <ryujin/scalar_conservation/flux.h>
 
namespace ryujin
{
  namespace Fluxes
  {
    class KPP : public Flux
    {
    public:
      KPP(const std::string &subsection)
          : Flux("kpp", subsection)
      {
        flux_formula_ = "f(u)={sin(u),cos(u)}";
      }
 
 
      double value(const double state,
                   const unsigned int direction) const override
      {
        switch (direction) {
        case 0:
          return std::sin(state);
        case 1:
          return std::cos(state);
        default:
          AssertThrow(false,
                      dealii::ExcMessage(
                          "KPP is only defined in (1 or) 2 space dimensions"));
          __builtin_trap();
        }
      }
 
 
      double gradient(const double state,
                      const unsigned int direction) const override
      {
        switch (direction) {
        case 0:
          return std::cos(state);
        case 1:
          return -std::sin(state);
        default:
          AssertThrow(false,
                      dealii::ExcMessage(
                          "KPP is only defined in (1 or) 2 space dimensions"));
          __builtin_trap();
        }
      }
    };
  } // namespace Fluxes
} // namespace ryujin