Port FluidSim core and scenarios to C++20

include/FluidSim/Component.hpp

@@ -0,0 +1,27 @@
+#pragma once
+
+#include <vector>
+
+namespace fluidsim::port {
+
+struct Port {
+    float mass_flow{};        // kg/s, positive into the owning component
+    float enthalpy{};         // J/kg
+    float pressure{101325.0f};
+    float density{1.1768f};
+    float temperature{300.0f};
+    float air_fraction{1.0f};
+    float* owner_air_mass{};
+    float* owner_exhaust_mass{};
+};
+
+// Small equivalent of the C# IComponent lifecycle. Components update their
+// conserved state after the coupled 1-D pipe solve has accumulated port flow.
+class Component {
+public:
+    virtual ~Component() = default;
+    virtual std::vector<Port*> ports() = 0;
+    virtual void update_state(float dt) = 0;
+};
+
+} // namespace fluidsim::port