Helmholtz testing (no decay bug)
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@@ -1,176 +1,91 @@
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using System;
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using System;
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using SFML.Graphics;
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using SFML.System;
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using FluidSim.Components;
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using FluidSim.Core;
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using FluidSim.Utils;
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namespace FluidSim.Tests
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{
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public class TestScenario : Scenario
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{
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// Engine
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private Cylinder cylinder;
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private Crankshaft crankshaft;
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// Intake side
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private Pipe1D intakePipeBeforeThrottle;
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private Volume0D intakePlenum; // 5 mL
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private Pipe1D intakeRunner;
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// Exhaust side
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private Pipe1D exhaustPipe;
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// Links
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private OpenEndLink intakeOpenEnd;
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private OrificeLink throttleOrifice;
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private OrificeLink plenumToRunner;
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private OrificeLink intakeValve;
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private OrificeLink exhaustValve;
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private OpenEndLink exhaustOpenEnd;
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private PipeSystem pipeSystem;
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private BoundarySystem boundaries;
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private Solver solver;
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private SoundProcessor exhaustSoundProcessor;
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private SoundProcessor intakeSoundProcessor;
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private OutdoorExhaustReverb reverb;
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private int[] pipeStart = { 0 };
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private int[] pipeEnd;
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private double dt;
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private int stepCount;
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// ---------- Throttle control ----------
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public double MaxThrottleArea { get; set; } = 1 * Units.cm2; // 2 cm²
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// Sound output: use pressure at open end
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private SoundProcessor openEndSound;
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private int openEndIdx = 0; // index of the open end in BoundarySystem (we added only one)
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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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solver = new Solver();
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const int cellCount = 200;
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float length = 2f;
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float dia = 0.02f;
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float area = MathF.PI * 0.25f * dia * dia;
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float[] areas = new float[cellCount];
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float[] dxs = new float[cellCount];
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float dx = length / cellCount;
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for (int i = 0; i < cellCount; i++)
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{
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areas[i] = area;
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dxs[i] = dx;
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}
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pipeEnd = new[] { cellCount };
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float rho0 = 101325f / (287f * 300f);
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pipeSystem = new PipeSystem(cellCount, pipeStart, pipeEnd, areas, dxs,
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rho0, 0f, 101325f);
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pipeSystem.DampingMultiplier = 0f;
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pipeSystem.EnergyRelaxationRate = 0f;
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pipeSystem.AmbientPressure = 101325f;
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// Pressure bubble near right end
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float pBubble = 10f * 101325f;
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float TBubble = 2000f;
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float rhoBubble = pBubble / (287f * TBubble);
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for (int i = 0; i <= 10; i++)
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pipeSystem.SetCellState(i, rhoBubble, 0f, pBubble);
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// Boundaries: left closed, right open
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boundaries = new BoundarySystem(pipeSystem, maxOrifices: 1, maxOpenEnds: 1);
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boundaries.AddOrifice(null, pipeIndex: 0, isLeftEnd: true, areaIndex: 0, 1f);
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boundaries.AddOpenEnd(pipeIndex: 0, isLeftEnd: false, 101325f, area);
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float[] orificeAreas = new float[1] { 0f };
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boundaries.SetOrificeAreas(orificeAreas);
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solver = new Solver { SubStepCount = 3};
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solver.SetTimeStep(dt);
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solver.CflTarget = 0.9;
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solver.SetPipeSystem(pipeSystem);
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solver.SetBoundarySystem(boundaries);
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// ---- Crankshaft (external, passed to cylinder) ----
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crankshaft = new Crankshaft(600);
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crankshaft.Inertia = 0.2;
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crankshaft.FrictionConstant = 2;
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crankshaft.FrictionViscous = 0.04;
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solver.EnableProfiling = true;
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pipeSystem.EnableProfiling = true;
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// ---- Cylinder ----
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double bore = 0.056, stroke = 0.057, conRod = 0.110, compRatio = 9.2;
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double ivo = 350.0, ivc = 580.0, evo = 120.0, evc = 370.0;
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cylinder = new Cylinder(bore, stroke, conRod, compRatio, ivo, ivc, evo, evc, crankshaft)
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{
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IntakeValveDiameter = 30 * Units.mm, // 30 mm
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IntakeValveLift = 5 * Units.mm, // 5 mm
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ExhaustValveDiameter = 28 * Units.mm, // 28 mm
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ExhaustValveLift = 5 * Units.mm // 5 mm
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};
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solver.AddComponent(cylinder);
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double pipeDiameter = 2 * Units.cm;
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double pipeArea = Units.AreaFromDiameter(pipeDiameter);
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exhaustSoundProcessor = new SoundProcessor(sampleRate, 1, pipeDiameter) { Gain = 0.1f };
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intakeSoundProcessor = new SoundProcessor(sampleRate, 1, pipeDiameter) { Gain = 0.1f };
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reverb = new OutdoorExhaustReverb(sampleRate);
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// ---- Pipes ----
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intakePipeBeforeThrottle = new Pipe1D(0.2, pipeArea, 10);
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intakeRunner = new Pipe1D(0.2, pipeArea, 10);
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exhaustPipe = new Pipe1D(0.5, pipeArea, 50);
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solver.AddComponent(intakePipeBeforeThrottle);
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solver.AddComponent(intakeRunner);
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solver.AddComponent(exhaustPipe);
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intakePlenum = new Volume0D(5 * Units.mL, 101325.0, 300.0);
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var plenumInlet = intakePlenum.CreatePort();
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var plenumOutlet = intakePlenum.CreatePort();
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solver.AddComponent(intakePlenum);
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// ---- Intake open end ----
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intakeOpenEnd = new OpenEndLink(intakePipeBeforeThrottle, isLeftEnd: true)
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{
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AmbientPressure = 101325.0,
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Gamma = 1.4
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};
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solver.AddOpenEndLink(intakeOpenEnd);
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// ---- Throttle orifice (variable area) ----
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throttleOrifice = new OrificeLink(plenumInlet, intakePipeBeforeThrottle, isPipeLeftEnd: false,
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areaProvider: () => MaxThrottleArea * Math.Clamp(Throttle, 0.0001, 1))
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{
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DischargeCoefficient = 0.2,
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UseInertance = false
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};
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solver.AddOrificeLink(throttleOrifice);
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// ---- Plenum to runner (fixed area) ----
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plenumToRunner = new OrificeLink(plenumOutlet, intakeRunner, isPipeLeftEnd: true,
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areaProvider: () => pipeArea)
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{
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DischargeCoefficient = 1.0,
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UseInertance = false
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};
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solver.AddOrificeLink(plenumToRunner);
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// ---- Intake valve ----
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intakeValve = new OrificeLink(cylinder.IntakePort, intakeRunner, isPipeLeftEnd: false,
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areaProvider: () => cylinder.IntakeValveArea)
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{
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DischargeCoefficient = 1.0,
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UseInertance = false
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};
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solver.AddOrificeLink(intakeValve);
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// ---- Exhaust valve ----
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exhaustValve = new OrificeLink(cylinder.ExhaustPort, exhaustPipe, isPipeLeftEnd: true,
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areaProvider: () => cylinder.ExhaustValveArea)
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{
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DischargeCoefficient = 1.0,
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UseInertance = false
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};
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solver.AddOrificeLink(exhaustValve);
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// ---- Exhaust open end ----
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exhaustOpenEnd = new OpenEndLink(exhaustPipe, isLeftEnd: false)
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{
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AmbientPressure = 101325.0,
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Gamma = 1.4
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};
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solver.AddOpenEndLink(exhaustOpenEnd);
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// Simple sound processor: convert mass flow rate to audio
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openEndSound = new SoundProcessor(sampleRate, 1f) { Gain = 2f };
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Console.WriteLine("Pulse test ready.");
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stepCount = 0;
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Console.WriteLine("4‑Stroke engine test (plenum + two pipes)");
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Console.WriteLine($"Bore {bore * 1000:F0}mm, Stroke {stroke * 1000:F0}mm, CR {compRatio}");
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Console.WriteLine($"IVO {ivo}°, IVC {ivc}°, EVO {evo}°, EVC {evc}° (no overlap)");
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}
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public override float Process()
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{
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cylinder.Crankshaft.Step(dt);
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cylinder.PreStep(dt);
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solver.Step();
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stepCount++;
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if (stepCount % 10000 == 0)
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{
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double crankDeg = cylinder.Crankshaft.CrankAngle * 180.0 / Math.PI % 720.0;
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double cylP = cylinder.Pressure / 1e5;
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double cylT = cylinder.Temperature;
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double cylMass = cylinder.Mass * 1e6;
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double mdotI = intakeValve.LastMassFlowRate;
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double mdotE = exhaustValve.LastMassFlowRate;
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double pipeR = exhaustPipe.GetCellPressure(exhaustPipe.CellCount - 1) / 1e5;
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double plenumP = intakePlenum.Pressure / 1e5;
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double actualArea = MaxThrottleArea * Throttle;
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float flow = boundaries.GetOpenEndMassFlow(openEndIdx);
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float sample = openEndSound.Process(flow);
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Console.WriteLine($"Step {stepCount}: Angle={crankDeg:F1}°, " +
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$"CylP={cylP:F2} bar, T={cylT:F0} K, mass={cylMass:F1} mg, " +
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$"mdotI={mdotI:E4} kg/s, mdotE={mdotE:E4} kg/s, PipeR={pipeR:F2} bar");
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Console.WriteLine($"Throttle = {Throttle * 100:F0}% area = {actualArea * 1e6:F2} mm², Plenum P = {plenumP:F3} bar");
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}
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float exhaustDry = exhaustSoundProcessor.Process(exhaustOpenEnd);
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float intakeDry = intakeSoundProcessor.Process(intakeOpenEnd);
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return reverb.Process(exhaustDry + intakeDry);
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return sample;
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}
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public override void Draw(RenderWindow target)
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@@ -178,56 +93,10 @@ namespace FluidSim.Tests
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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 intakeY = winH / 2f - 40f;
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float exhaustY = winH / 2f + 80f;
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// Open end marker
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float openEndX = 40f;
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var openEndMark = new CircleShape(5f) { FillColor = Color.Cyan };
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openEndMark.Position = new Vector2f(openEndX - 5f, intakeY - 5f);
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target.Draw(openEndMark);
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// First intake pipe
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float pipe1StartX = openEndX;
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float pipe1EndX = pipe1StartX + 120f;
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DrawPipe(target, intakePipeBeforeThrottle, intakeY, pipe1StartX, pipe1EndX);
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// Throttle symbol
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float throttleX = pipe1EndX + 5f;
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var throttleRect = new RectangleShape(new Vector2f(8f, 30f))
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{
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FillColor = Color.Yellow,
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Position = new Vector2f(throttleX, intakeY - 15f)
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};
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target.Draw(throttleRect);
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// Plenum
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float plenW = 60f, plenH = 80f;
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float plenLeftX = throttleX + 10f;
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float plenCenterX = plenLeftX + plenW / 2f;
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float plenTopY = intakeY - plenH / 2f;
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DrawVolume(target, intakePlenum, plenCenterX, plenTopY, plenW, plenH);
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// Runner pipe
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float runnerStartX = plenLeftX + plenW + 5f;
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float runnerEndX = runnerStartX + 100f;
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DrawPipe(target, intakeRunner, intakeY, runnerStartX, runnerEndX);
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// Cylinder
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float cylCX = runnerEndX + 50f;
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float cylTopY = intakeY - 120f;
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float cylW = 80f, cylMaxH = 240f;
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DrawCylinder(target, cylinder, cylCX, cylTopY, cylW, cylMaxH);
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// Exhaust pipe
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float exhStartX = cylCX + cylW / 2f + 20f;
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float exhEndX = winW - 60f;
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DrawPipe(target, exhaustPipe, exhaustY, exhStartX, exhEndX);
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// Exhaust open end marker
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var exhOpenEndMark = new CircleShape(5f) { FillColor = Color.Magenta };
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exhOpenEndMark.Position = new Vector2f(exhEndX - 5f, exhaustY - 5f);
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target.Draw(exhOpenEndMark);
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float startX = 50f;
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float endX = winW - 50f;
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float y = winH / 2f;
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DrawPipe(target, pipeSystem, 0, y, startX, endX);
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}
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}
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}
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