MeanField_SERiF/tests/eos/polytropic_eos_relations.cpp

// Ported from MeanField tests/physics/polytropic_eos_relations.cpp.

#include <array>
#include <cmath>
#include <limits>
#include <string_view>

#include <catch2/catch_test_macros.hpp>
#include <catch2/matchers/catch_matchers_floating_point.hpp>

#include "serif/eos/evaluation.hpp"
#include "serif/eos/exceptions.hpp"
#include "serif/eos/models/polytropic.hpp"

#include "serif/tests/test_tags.hpp"

namespace eos = serif::eos;
namespace dimensions = serif::dimensions;

TEST_CASE(
    "Polytropic EOS Typed Relations Preserve Analytic Values",
    tags::unit & tags::eos
) {
    constexpr std::array<double, 3> polytropic_indices{1.0, 1.5, 3.0};
    constexpr std::array<double, 2> polytropic_constants{0.25, 0.73};
    constexpr std::array<double, 4> densities{0.0, 1.0e-6, 0.2, 2.0};
    constexpr std::array<double, 4> specific_enthalpies{-0.3, 0.0, 0.2, 1.7};
    constexpr std::array<double, 4> pressures{0.0, 1.0e-8, 0.3, 4.0};

    for (const double polytropic_index : polytropic_indices) {
        for (const double polytropic_constant : polytropic_constants) {
            const eos::models::Polytrope equation_of_state(polytropic_index, polytropic_constant);

            for (const double density : densities) {
                CAPTURE(polytropic_index, polytropic_constant, density);

                const double expected_pressure = polytropic_constant * std::pow(density, 1.0 + 1.0 / polytropic_index);
                const double expected_specific_enthalpy =
                    (polytropic_index + 1.0) * polytropic_constant * std::pow(density, 1.0 / polytropic_index);

                CHECK(
                    eos::evaluate<dimensions::Pressure>(equation_of_state, dimensions::DensityValue{density}).value() ==
                    expected_pressure
                );

                CHECK(
                    eos::evaluate<dimensions::SpecificEnthalpy>(equation_of_state, dimensions::DensityValue{density})
                        .value() == expected_specific_enthalpy
                );

                CHECK_THAT(
                    (eos::partial_derivative<dimensions::Pressure, dimensions::MassDensity>(
                        equation_of_state, dimensions::DensityValue{density}
                    )
                            .value()),
                    Catch::Matchers::WithinRel(
                        density == 0.0 ? 0.0 : expected_specific_enthalpy / polytropic_index, 2.0e-15
                    )
                );
            }

            for (const double specific_enthalpy : specific_enthalpies) {
                CAPTURE(polytropic_index, polytropic_constant, specific_enthalpy);

                const double expected_density =
                    specific_enthalpy <= 0.0
                        ? 0.0
                        : std::pow(
                              specific_enthalpy / ((polytropic_index + 1.0) * polytropic_constant), polytropic_index
                          );

                CHECK(
                    eos::evaluate<dimensions::MassDensity>(
                        equation_of_state, dimensions::SpecificEnthalpyValue{specific_enthalpy}
                    )
                        .value() == expected_density
                );

                CHECK(
                    eos::evaluate<dimensions::Pressure>(
                        equation_of_state, dimensions::SpecificEnthalpyValue{specific_enthalpy}
                    )
                        .value() ==
                    (specific_enthalpy <= 0.0 ? 0.0 : expected_density * specific_enthalpy / (polytropic_index + 1.0))
                );

                CHECK(
                    (eos::partial_derivative<dimensions::Pressure, dimensions::SpecificEnthalpy>(
                         equation_of_state, dimensions::SpecificEnthalpyValue{specific_enthalpy}
                     )
                            .value() == expected_density)
                );
            }

            for (const double pressure : pressures) {
                CAPTURE(polytropic_index, polytropic_constant, pressure);

                const double index_plus_one = polytropic_index + 1.0;
                const double expected_specific_enthalpy =
                    index_plus_one * std::pow(polytropic_constant, polytropic_index / index_plus_one) *
                    std::pow(pressure, 1.0 / index_plus_one);

                CHECK(
                    eos::evaluate<dimensions::SpecificEnthalpy>(equation_of_state, dimensions::PressureValue{pressure})
                        .value() == expected_specific_enthalpy
                );
            }
        }
    }
}

TEST_CASE(
    "Typed Polytropic EOS Preserves Domain And Exterior Semantics",
    tags::unit & tags::eos
) {
    const eos::models::Polytrope equation_of_state(3.0, 0.75);

    try {
        static_cast<void>(eos::evaluate<dimensions::Pressure>(equation_of_state, dimensions::DensityValue{-0.1}));
        FAIL("A negative density must be rejected.");
    } catch (const eos::EOSEvaluationError& error) {
        CHECK(std::string_view{error.what()}.find("EOS_INVALID_THERMODYNAMIC_INPUT") != std::string_view::npos);
    }

    try {
        static_cast<void>(eos::evaluate<dimensions::SpecificEnthalpy>(
            equation_of_state, dimensions::PressureValue{std::numeric_limits<double>::quiet_NaN()}
        ));
        FAIL("A nonfinite pressure must be rejected.");
    } catch (const eos::EOSEvaluationError& error) {
        CHECK(std::string_view{error.what()}.find("EOS_INVALID_THERMODYNAMIC_INPUT") != std::string_view::npos);
    }

    constexpr double exterior_specific_enthalpy = -0.3;

    CHECK(
        eos::evaluate<dimensions::MassDensity>(
            equation_of_state, dimensions::SpecificEnthalpyValue{exterior_specific_enthalpy}
        )
            .value() == 0.0
    );

    CHECK(
        eos::evaluate<dimensions::Pressure>(
            equation_of_state, dimensions::SpecificEnthalpyValue{exterior_specific_enthalpy}
        )
            .value() == 0.0
    );

    CHECK(
        (eos::partial_derivative<dimensions::MassDensity, dimensions::SpecificEnthalpy>(
             equation_of_state, dimensions::SpecificEnthalpyValue{exterior_specific_enthalpy}
         )
                .value() == 0.0)
    );

    CHECK(
        (eos::partial_derivative<dimensions::Pressure, dimensions::SpecificEnthalpy>(
             equation_of_state, dimensions::SpecificEnthalpyValue{exterior_specific_enthalpy}
         )
                .value() == 0.0)
    );
}

TEST_CASE("Density based polytropic EOS supplies surface density and bulk Newton curvature", tags::unit & tags::eos) {
    for (const double index : {1.0, 1.5, 2.0, 2.5, 3.0}) {
        const eos::models::Polytrope model(index, 0.73);
        for (const double density : {1.0e-6, 0.2, 2.0}) {
            CAPTURE(index, density);
            const dimensions::DensityValue state{density};
            const auto pressure = eos::evaluate<dimensions::Pressure>(model, state);
            const double recovered = eos::evaluate<dimensions::MassDensity>(model, pressure).value();
            CHECK_THAT(recovered, Catch::Matchers::WithinRel(density, 3.0e-15));
            const double step = density * 1.0e-4;
            const double plus = eos::partial_derivative<dimensions::Pressure, dimensions::MassDensity>(
                model, dimensions::DensityValue{density + step}).value();
            const double minus = eos::partial_derivative<dimensions::Pressure, dimensions::MassDensity>(
                model, dimensions::DensityValue{density - step}).value();
            const double derivative = eos::second_partial_derivative<dimensions::Pressure, dimensions::MassDensity, dimensions::MassDensity>(model, state).value();
            CHECK_THAT(derivative, Catch::Matchers::WithinRel((plus - minus) / (2.0 * step), 3.0e-9));
        }
        CHECK(eos::evaluate<dimensions::MassDensity>(model, dimensions::PressureValue{0.0}).value() == 0.0);
        if (index == 1.0) {
            CHECK((eos::second_partial_derivative<dimensions::Pressure, dimensions::MassDensity, dimensions::MassDensity>(
                model, dimensions::DensityValue{0.0}).value() == 1.46));
        } else {
            CHECK_THROWS_AS((eos::second_partial_derivative<dimensions::Pressure, dimensions::MassDensity, dimensions::MassDensity>(
                model, dimensions::DensityValue{0.0})), eos::EOSEvaluationError);
        }
        for (const double invalid : {-0.1, std::numeric_limits<double>::infinity(), std::numeric_limits<double>::quiet_NaN()}) {
            CHECK_THROWS_AS(eos::evaluate<dimensions::MassDensity>(model, dimensions::PressureValue{invalid}), eos::EOSEvaluationError);
            CHECK_THROWS_AS((eos::second_partial_derivative<dimensions::Pressure, dimensions::MassDensity, dimensions::MassDensity>(
                model, dimensions::DensityValue{invalid})), eos::EOSEvaluationError);
        }
    }
}