Add turbocharged twin scenario and cross-platform test harness

tests/intake_regression.cpp

@@ -0,0 +1,51 @@
+#include "FluidSim/Scenario.hpp"
+#include <cmath>
+#include <iostream>
+#include <stdexcept>
+using namespace fluidsim::port;
+namespace {
+void check(bool condition, const char *message) {
+    if (!condition)
+        throw std::runtime_error(message);
+}
+void run(FourStrokeTwinScenario &s, float seconds, float pedal) {
+    s.throttle = pedal;
+    for (int i = 0; i < int(std::lround(seconds * 44100)); ++i) {
+        const auto audio = s.process();
+        check(std::isfinite(audio.left) && std::isfinite(audio.right), "nonfinite transient audio");
+    }
+}
+} // namespace
+int main() {
+    FourStrokeTwinScenario s;
+    run(s, 3, 0);
+    run(s, .5f, .8f);
+    run(s, 4.5f, 0);
+    const float idle_map = s.intake_plenum.pressure();
+    check(idle_map > 20000 && idle_map < 80000, "idle MAP did not recover after first blip");
+    run(s, 1, 1);
+    const float open_map = s.intake_plenum.pressure();
+    const float open_temperature = s.intake_plenum.temperature();
+    const auto inlet = s.pipes.front().state(0);
+    const float inlet_temperature = inlet.pressure / (inlet.rho * gas_constant);
+    check(open_map > 75000 && open_map > idle_map + 20000,
+          "opening throttle did not relieve manifold vacuum");
+    check(open_temperature > 250 && open_temperature < 400,
+          "fresh charge heats progressively after repeated blips");
+    check(inlet_temperature > 280 && inlet_temperature < 320,
+          "inlet no longer supplies near-ambient fresh air");
+    check(std::abs(s.intake_atmosphere.port.temperature - 300) < .01f, "reservoir temperature drift");
+    check(std::abs(s.intake_atmosphere.port.air_fraction - 1) < 1e-6, "reservoir admits exhaust composition");
+    run(s, 7, 0);
+    const auto recovered = s.snapshot();
+    check(recovered.rpm > 1000 && recovered.rpm < 2600, "engine did not recover idle after second blip");
+    check(recovered.intake_pressure > 20000 && recovered.intake_pressure < 80000,
+          "manifold remains evacuated after idle recovery");
+    for (const auto &p : s.pipes)
+        check(p.positivity_repairs == 0, "intake transient required positivity repairs");
+    std::cout << "Intake regression passed: idle_MAP=" << idle_map / 1000
+              << " kPa, open_MAP=" << open_map / 1000 << " kPa, open_T=" << open_temperature
+              << " K, inlet_T=" << inlet_temperature
+              << " K, recovered_MAP=" << recovered.intake_pressure / 1000
+              << " kPa, recovered_RPM=" << recovered.rpm << '\n';
+}