General testing
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238
Scenarios/EngineScenario.cs
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238
Scenarios/EngineScenario.cs
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using System;
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using FluidSim.Components;
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using SFML.Graphics;
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using SFML.System;
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namespace FluidSim.Core
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{
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public class EngineScenario : Scenario
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{
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private Solver solver;
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private Volume0D cylinder;
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private Pipe1D exhaustPipe;
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private PipeVolumeConnection coupling;
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private SoundProcessor soundProcessor;
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private double dt;
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private double ambientPressure = 101325.0;
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private double time;
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// Crankshaft
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private double crankAngle = 0.0;
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private const double TargetRPM = 4000.0;
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private double angularVelocity;
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// Combustion
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private const double CombustionPressure = 8.0 * 101325.0;
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private const double CombustionTemperature = 1800.0;
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// Valve timing
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private const double ValveOpenStart = 120.0 * Math.PI / 180.0;
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private const double ValveOpenEnd = 480.0 * Math.PI / 180.0;
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private const double ValveRampWidth = 30.0 * Math.PI / 180.0;
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private double maxOrificeArea;
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// Misfire
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private Random rand = new Random();
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private const double MisfireProbability = 0.02;
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private bool isMisfiring = false;
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// Low‑pass filter for pressure
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private double lastFilteredPressure;
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private const double PressureCutoffHz = 50.0;
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// Logging
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private int stepCount = 0;
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private const int LogStepInterval = 1000;
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private int combustionCount = 0;
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private int misfireCount = 0;
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public override void Initialize(int sampleRate)
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{
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dt = 1.0 / sampleRate;
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angularVelocity = TargetRPM * 2.0 * Math.PI / 60.0;
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// Cylinder: 0.5 litre, initially at ambient
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double cylVolume = 0.5e-3;
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double initialPressure = ambientPressure;
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double initialTemperature = 300.0;
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cylinder = new Volume0D(cylVolume, initialPressure, initialTemperature, sampleRate)
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{
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Gamma = 1.4,
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GasConstant = 287.0
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};
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// Exhaust pipe: length 2.5 m, radius 2 cm
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double pipeLength = 2.5;
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double pipeRadius = 0.02;
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double pipeArea = Math.PI * pipeRadius * pipeRadius;
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maxOrificeArea = pipeArea;
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exhaustPipe = new Pipe1D(pipeLength, pipeArea, sampleRate, forcedCellCount: 70);
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exhaustPipe.SetUniformState(1.225, 0.0, ambientPressure);
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// Coupling (valve starts closed)
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coupling = new PipeVolumeConnection(cylinder, exhaustPipe, true, orificeArea: 0.0);
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solver = new Solver();
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solver.SetTimeStep(dt);
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solver.AddVolume(cylinder);
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solver.AddPipe(exhaustPipe);
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solver.AddConnection(coupling);
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// Use ZeroPressureOpen for strong reflections
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solver.SetPipeBoundary(exhaustPipe, false, BoundaryType.ZeroPressureOpen, ambientPressure);
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// Sound processor (tuned to pipe length)
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soundProcessor = new SoundProcessor(sampleRate, pipeLength, pipeRadius * 2, reverbTimeMs: 200.0f);
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soundProcessor.MasterGain = 0.02f; // boosted from 0.0008
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soundProcessor.PressureGain = 4.0f; // boosted from6 0.12
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soundProcessor.TurbulenceGain = 0.0002f; // reduced from 0.02
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soundProcessor.SetAmbientPressure(ambientPressure);
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lastFilteredPressure = ambientPressure;
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Console.WriteLine("=== EngineScenario (ZeroPressureOpen, boosted gains) ===");
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Console.WriteLine($"Target RPM: {TargetRPM}, Misfire prob: {MisfireProbability * 100:F1}%");
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Console.WriteLine($"Pipe length: {pipeLength} m, fundamental: {340/(4*pipeLength):F1} Hz");
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Console.WriteLine($"Valve opens at {ValveOpenStart*180/Math.PI:F0}°, closes at {ValveOpenEnd*180/Math.PI:F0}°, ramp {ValveRampWidth*180/Math.PI:F0}°");
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Console.WriteLine($"Sample rate: {sampleRate} Hz, dt = {dt*1000:F3} ms");
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Console.WriteLine("Time[s] Crank[°] Valve[%] MassFlow[kg/s] Comb# Misfire");
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Console.WriteLine("---------------------------------------------------------");
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}
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private double ValveOpenRatio(double crankRad)
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{
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double cycleAngle = crankRad % (4.0 * Math.PI);
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double openStart = ValveOpenStart;
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double openEnd = ValveOpenEnd;
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if (cycleAngle < openStart || cycleAngle > openEnd)
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return 0.0;
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double fullOpenWindow = openEnd - openStart;
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double closedWindow = 2.0 * ValveRampWidth;
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if (fullOpenWindow <= closedWindow)
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return 1.0;
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double tmid = (openStart + openEnd) / 2.0;
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double dist = Math.Abs(cycleAngle - tmid);
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double rampHalf = (fullOpenWindow - closedWindow) / 2.0;
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if (dist <= rampHalf)
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return 1.0;
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else
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{
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double frac = (dist - rampHalf) / ValveRampWidth;
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frac = Math.Clamp(frac, 0.0, 1.0);
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double lift = Math.Cos(frac * Math.PI / 2.0);
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return lift * lift;
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}
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}
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public override float Process()
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{
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// Update crank angle
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crankAngle += angularVelocity * dt;
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if (crankAngle >= 2.0 * Math.PI)
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{
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crankAngle -= 2.0 * Math.PI;
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isMisfiring = rand.NextDouble() < MisfireProbability;
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}
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// Power stroke at TDC
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if (crankAngle < angularVelocity * dt && crankAngle >= 0.0)
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{
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if (isMisfiring)
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{
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double vol = cylinder.Volume;
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double R = cylinder.GasConstant;
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double T0 = 300.0;
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double newMass = ambientPressure * vol / (R * T0);
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double newInternalEnergy = ambientPressure * vol / (cylinder.Gamma - 1.0);
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cylinder.Mass = newMass;
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cylinder.InternalEnergy = newInternalEnergy;
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misfireCount++;
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}
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else
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{
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double volume = cylinder.Volume;
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double gamma = cylinder.Gamma;
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double newInternalEnergy = CombustionPressure * volume / (gamma - 1.0);
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double R = cylinder.GasConstant;
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double newMass = CombustionPressure * volume / (R * CombustionTemperature);
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cylinder.InternalEnergy = newInternalEnergy;
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cylinder.Mass = newMass;
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combustionCount++;
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}
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}
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// Update valve area
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double valveOpen = ValveOpenRatio(crankAngle);
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coupling.OrificeArea = maxOrificeArea * valveOpen;
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float massFlow = solver.Step();
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float endPressure = (float)exhaustPipe.GetCellPressure(exhaustPipe.GetCellCount() - 1);
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// Low‑pass filter the pressure (emphasise low frequencies)
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double rc = 1.0 / (2.0 * Math.PI * PressureCutoffHz);
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double alpha = dt / (rc + dt);
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double filteredPressure = alpha * endPressure + (1.0 - alpha) * lastFilteredPressure;
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lastFilteredPressure = filteredPressure;
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float audioSample = soundProcessor.Process(massFlow, (float)filteredPressure);
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time += dt;
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stepCount++;
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// Logging
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if (stepCount % LogStepInterval == 0 || (crankAngle < angularVelocity * dt * 2 && !isMisfiring && combustionCount > 0))
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{
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Console.WriteLine($"{time,7:F3} {crankAngle * 180.0 / Math.PI,6:F1} " +
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$"{valveOpen * 100,6:F1} {massFlow,10:F4} " +
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$"{combustionCount,3} {(isMisfiring ? "X" : "")}");
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}
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return audioSample;
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}
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public override void Draw(RenderWindow target)
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{
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float winW = target.GetView().Size.X;
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float winH = target.GetView().Size.Y;
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float centerY = winH / 2f;
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float cylW = 80f, cylH = 150f;
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var cylRect = new RectangleShape(new Vector2f(cylW, cylH));
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cylRect.Position = new Vector2f(40f, centerY - cylH / 2f);
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double pNorm = (cylinder.Pressure - ambientPressure) / ambientPressure;
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if (double.IsNaN(pNorm)) pNorm = 0;
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byte red = (byte)(Math.Clamp(pNorm * 128, 0, 255));
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byte blue = (byte)(Math.Clamp(-pNorm * 128, 0, 255));
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cylRect.FillColor = new Color(red, 0, blue);
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target.Draw(cylRect);
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int n = exhaustPipe.GetCellCount();
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float pipeStartX = 120f, pipeEndX = winW - 60f;
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float pipeLen = pipeEndX - pipeStartX;
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float dx = pipeLen / (n - 1);
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float baseRadius = 20f;
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var vertices = new Vertex[n * 2];
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for (int i = 0; i < n; i++)
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{
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float x = pipeStartX + i * dx;
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double p = exhaustPipe.GetCellPressure(i);
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float r = baseRadius * (float)(1.0 + (p - ambientPressure) / ambientPressure);
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if (r < 2f) r = 2f;
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double t = (p - ambientPressure) / ambientPressure;
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t = Math.Clamp(t, -1.0, 1.0);
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byte rCol = (byte)(t > 0 ? 255 * t : 0);
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byte bCol = (byte)(t < 0 ? -255 * t : 0);
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byte gCol = (byte)(255 * (1 - Math.Abs(t)));
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var col = new Color(rCol, gCol, bCol);
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vertices[i * 2] = new Vertex(new Vector2f(x, centerY - r), col);
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vertices[i * 2 + 1] = new Vertex(new Vector2f(x, centerY + r), col);
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}
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target.Draw(vertices, PrimitiveType.TriangleStrip);
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}
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}
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}
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