feat(libmeanfield): centrifugal + pressure

tests/physics/barotrope.cpp

@@ -0,0 +1,144 @@
+#include <array>
+#include <cmath>
+#include <limits>
+
+#include <catch2/catch_test_macros.hpp>
+#include <catch2/matchers/catch_matchers_floating_point.hpp>
+
+import mean_field;
+import test_helpers;
+
+TEST_CASE(
+    "Polytropic Barotrope Satisfies Its Analytic Identities",
+    tags::hydro &tags::unit &tags::barotrope
+) {
+    constexpr double polytropic_index    = 3.0;
+    constexpr double polytropic_constant = 1.5;
+
+    const mean_field::physics::PolytropicBarotrope barotrope(
+        polytropic_index, polytropic_constant
+    );
+
+    const std::array<double, 5> densities{1.0e-6, 1.0e-3, 0.1, 0.7, 2.0};
+
+    for (const double density : densities) {
+        const double pressure = barotrope.pressure_from_density(density);
+
+        const double enthalpy = barotrope.enthalpy_from_density(density);
+
+        const double reconstructed_density =
+            barotrope.density_from_enthalpy(enthalpy);
+
+        const double reconstructed_pressure =
+            barotrope.pressure_from_enthalpy(enthalpy);
+
+        CHECK_THAT(
+            reconstructed_density, Catch::Matchers::WithinRel(density, 2.0e-14)
+        );
+
+        CHECK_THAT(
+            reconstructed_pressure,
+            Catch::Matchers::WithinRel(pressure, 2.0e-14)
+        );
+
+        CHECK_THAT(
+            pressure, Catch::Matchers::WithinRel(
+                          density * enthalpy / (polytropic_index + 1.0), 2.0e-14
+                      )
+        );
+
+        CHECK_THAT(
+            barotrope.pressure_derivative_from_enthalpy(enthalpy),
+            Catch::Matchers::WithinRel(density, 2.0e-14)
+        );
+
+        CHECK_THAT(
+            barotrope.pressure_derivative_from_density(density),
+            Catch::Matchers::WithinRel(enthalpy / polytropic_index, 2.0e-14)
+        );
+    }
+}
+
+TEST_CASE(
+    "Polytropic Barotrope Derivatives Match Centered Differences",
+    tags::hydro &tags::jacobian &tags::unit &tags::barotrope
+) {
+    const mean_field::physics::PolytropicBarotrope barotrope(3.0, 1.5);
+
+    const std::array<double, 4> enthalpies{0.05, 0.2, 0.7, 1.4};
+
+    for (const double enthalpy : enthalpies) {
+        const double step = 1.0e-6 * std::max(1.0, enthalpy);
+
+        const double density_difference =
+            (barotrope.density_from_enthalpy(enthalpy + step) -
+             barotrope.density_from_enthalpy(enthalpy - step)) /
+            (2.0 * step);
+
+        const double pressure_difference =
+            (barotrope.pressure_from_enthalpy(enthalpy + step) -
+             barotrope.pressure_from_enthalpy(enthalpy - step)) /
+            (2.0 * step);
+
+        CHECK_THAT(
+            density_difference,
+            Catch::Matchers::WithinRel(
+                barotrope.density_derivative_from_enthalpy(enthalpy), 5.0e-10
+            )
+        );
+
+        CHECK_THAT(
+            pressure_difference,
+            Catch::Matchers::WithinRel(
+                barotrope.pressure_derivative_from_enthalpy(enthalpy), 5.0e-10
+            )
+        );
+    }
+}
+
+TEST_CASE(
+    "Polytropic Barotrope Has An Exact Zero Density Surface",
+    tags::hydro &tags::unit &tags::barotrope
+) {
+    const mean_field::physics::PolytropicBarotrope barotrope(3.0, 1.5);
+
+    CHECK(barotrope.density_from_enthalpy(-1.0) == 0.0);
+    CHECK(barotrope.density_from_enthalpy(0.0) == 0.0);
+
+    CHECK(barotrope.pressure_from_enthalpy(-1.0) == 0.0);
+    CHECK(barotrope.pressure_from_enthalpy(0.0) == 0.0);
+
+    CHECK(barotrope.density_derivative_from_enthalpy(-1.0) == 0.0);
+
+    CHECK(barotrope.density_derivative_from_enthalpy(0.0) == 0.0);
+
+    CHECK(barotrope.pressure_derivative_from_enthalpy(0.0) == 0.0);
+}
+
+TEST_CASE(
+    "Polytropic Barotrope Rejects Invalid Material Parameters",
+    tags::hydro &tags::unit
+) {
+    CHECK_THROWS_AS(
+        mean_field::physics::PolytropicBarotrope(0.5, 1.0),
+        std::invalid_argument
+    );
+
+    CHECK_THROWS_AS(
+        mean_field::physics::PolytropicBarotrope(3.0, 0.0),
+        std::invalid_argument
+    );
+
+    CHECK_THROWS_AS(
+        mean_field::physics::PolytropicBarotrope(
+            std::numeric_limits<double>::infinity(), 1.0
+        ),
+        std::invalid_argument
+    );
+
+    const mean_field::physics::PolytropicBarotrope barotrope(3.0, 1.0);
+
+    CHECK_THROWS_AS(barotrope.pressure_from_density(-1.0), std::domain_error);
+
+    CHECK_THROWS_AS(barotrope.enthalpy_from_density(-1.0), std::domain_error);
+}