equation_of_state_noble_abel_stiffened_gas.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 "equation_of_state.h"
 
namespace ryujin
{
  namespace EquationOfStateLibrary
  {
    class NobleAbelStiffenedGas : public EquationOfState
    {
    public:
      using EquationOfState::pressure;
      using EquationOfState::specific_internal_energy;
      using EquationOfState::speed_of_sound;
      using EquationOfState::temperature;
 
      NobleAbelStiffenedGas(const std::string &subsection)
          : EquationOfState("noble abel stiffened gas", subsection)
      {
        gamma_ = 7. / 5.;
        this->add_parameter("gamma", gamma_, "The ratio of specific heats");
 
        /*
         * R is the specific gas constant with units [J / (Kg K)]. More details
         * can be found at:
         * https://en.wikipedia.org/wiki/Gas_constant#Specific_gas_constant
         */
        R_ = 287.052874;
        this->add_parameter(
            "gas constant R", R_, "The specific gas constant R");
 
        cv_ = R_ / (gamma_ - 1.);
 
        b_ = 0.;
        this->add_parameter(
            "covolume b", b_, "The maximum compressibility constant");
 
        q_ = 0.;
        this->add_parameter("reference specific internal energy",
                            q_,
                            "The reference specific internal energy");
 
        pinf_ = 0.;
        this->add_parameter(
            "reference pressure", pinf_, "The reference pressure p infinity");
 
        s0_ = 0.;
        this->add_parameter("reference specific entropy",
                            s0_,
                            "The reference specific entropy");
 
        /* Update the EOS interpolation parameters on parameter read in
         * and specific heat at constant volume:
         */
        ParameterAcceptor::parse_parameters_call_back.connect([this] {
          this->covolume_constant_ = b_;
          this->interpolation_pinfty_ = pinf_;
          this->interpolation_q_ = q_;
          cv_ = R_ / (gamma_ - 1.);
        });
      }
 
      double pressure(double rho, double e) const final
      {
        return (gamma_ - 1.) * rho * (e - q_) / (1. - b_ * rho) -
               gamma_ * pinf_;
      }
 
 
      double specific_internal_energy(double rho, double p) const final
      {
        const auto numerator = (p + gamma_ * pinf_) * (1. - b_ * rho);
        const auto denominator = rho * (gamma_ - 1.);
        return q_ + numerator / denominator;
      }
 
      double temperature(double rho, double e) const final
      {
        return (e - q_ - pinf_ * (1. / rho - b_)) / cv_;
      }
 
      double cold_curve_bound(double rho) const final
      {
        return q_ + pinf_ * (1. / rho - b_);
      }
 
      double specific_entropy(double rho, double e) const final
      {
        const auto covolume_term = 1. / rho - b_;
        const auto p_plus_pinf =
            (gamma_ - 1.) * ((e - q_) - pinf_ * covolume_term) / covolume_term;
        const auto first_term = cv_ * std::log(p_plus_pinf);
        const auto second_term =
            cv_ * gamma_ * std::log((gamma_ - 1.) * cv_ / covolume_term);
        return first_term - second_term + s0_;
      }
 
      double speed_of_sound(double rho, double e) const final
      {
        const auto covolume = 1. - b_ * rho;
        auto radicand =
            (rho * (e - q_) - pinf_ * covolume) / (covolume * covolume * rho);
        radicand *= gamma_ * (gamma_ - 1.);
        return std::sqrt(radicand);
      }
 
    private:
      double gamma_;
      double R_;
      double cv_;
      double b_;
      double q_;
      double pinf_;
      double s0_;
    };
  } // namespace EquationOfStateLibrary
} /* namespace ryujin */