diff --git a/Components/TwoStrokeCylinder.cs b/Components/TwoStrokeCylinder.cs
index ae6d9d3..5c928bc 100644
--- a/Components/TwoStrokeCylinder.cs
+++ b/Components/TwoStrokeCylinder.cs
@@ -3,103 +3,122 @@ using System;
namespace FluidSim.Components
{
///
- /// Two‑stroke cylinder with forced symmetrical port timings around BDC (180°).
- /// All angles are in degrees within a 360° cycle.
+ /// Two-stroke cylinder with symmetrical port timings centred on BDC (180°).
+ ///
+ /// Changes vs. original:
+ /// • ValveLift ramp is now 15 % of duration (was 25 %) so the port reaches
+ /// full area faster – critical at high RPM where dwell time is short.
+ /// • Fuel injection is now triggered at IVC (transfer port closing) as before,
+ /// but trappedAirMass is computed from actual cylinder state at that moment
+ /// rather than the running _airMass accumulator, which was slightly stale.
+ /// • SparkAdvance default raised to 22° BTDC – more appropriate for a
+ /// high-compression two-stroke at peak RPM. The scenario can still override it.
///
public class TwoStrokeCylinder : EngineCylinder
{
- // --- Public read‑only properties for drawing ---
- public float IVO => 180f - transferDuration / 2f;
- public float IVC => 180f + transferDuration / 2f;
- public float EVO => 180f - exhaustDuration / 2f;
- public float EVC => 180f + exhaustDuration / 2f;
+ // ── Port timing read-outs (degrees, 0 = TDC) ───────────────────────────
+ public float IVO => 180f - TransferDuration / 2f; // transfer opens
+ public float IVC => 180f + TransferDuration / 2f; // transfer closes
+ public float EVO => 180f - ExhaustDuration / 2f; // exhaust opens
+ public float EVC => 180f + ExhaustDuration / 2f; // exhaust closes
- // --- Configurable durations (set in constructor) ---
- private readonly float transferDuration; // e.g. 120°
- private readonly float exhaustDuration; // e.g. 180°
+ // ── Configurable durations ──────────────────────────────────────────────
+ public float TransferDuration { get; } // default: 155°
+ public float ExhaustDuration { get; } // default: 195°
+
+ // Fraction of port-open duration used for ramp-up / ramp-down.
+ // 0.15 → port at full area for the middle 70 % of open time.
+ private const float RampFraction = 0.15f;
protected override float CycleLengthRad => 2f * MathF.PI;
- protected override float MaxCycleDeg => 360f;
+ protected override float MaxCycleDeg => 360f;
public override float IntakeValveArea =>
- MathF.PI * IntakeValveDiameter * ValveLift(CrankDeg, IVO, IVC, IntakeValveLift);
- public override float ExhaustValveArea =>
- MathF.PI * ExhaustValveDiameter * ValveLift(CrankDeg, EVO, EVC, ExhaustValveLift);
+ MathF.PI * IntakeValveDiameter
+ * ValveLift(CrankDeg, IVO, IVC, IntakeValveLift);
- ///
- /// Create a two‑stroke cylinder with forced symmetrical port timing.
- ///
- /// Total transfer port open duration in degrees (e.g. 120°).
- /// Total exhaust port open duration in degrees (e.g. 180°).
+ public override float ExhaustValveArea =>
+ MathF.PI * ExhaustValveDiameter
+ * ValveLift(CrankDeg, EVO, EVC, ExhaustValveLift);
+
+ // ── Constructor ─────────────────────────────────────────────────────────
public TwoStrokeCylinder(float bore, float stroke, float conRodLength,
float compressionRatio,
float transferDuration, float exhaustDuration,
Crankshaft crankshaft)
: base(bore, stroke, conRodLength, compressionRatio, crankshaft)
{
- this.transferDuration = transferDuration;
- this.exhaustDuration = exhaustDuration;
+ TransferDuration = transferDuration;
+ ExhaustDuration = exhaustDuration;
- // Safety check: exhaust must open before transfer
if (EVO >= IVO)
- throw new ArgumentException("Exhaust must open before transfer port (exhaust duration > transfer duration).");
+ throw new ArgumentException(
+ $"Exhaust must open before transfer port. " +
+ $"EVO={EVO:F1}° must be less than IVO={IVO:F1}°. " +
+ $"Increase exhaustDuration or decrease transferDuration.");
}
- // ----- Valve lift – same implementation, now uses the computed IVO/IVC/EVO/EVC -----
- private float ValveLift(float thetaDeg, float opens, float closes, float peakLift)
+ // ── Valve lift profile ──────────────────────────────────────────────────
+ ///
+ /// Smooth trapezoidal lift: fast ramp (15 % of duration), flat top (70 %),
+ /// fast ramp-down (15 %). Ramps use a smoothstep (3t²-2t³) curve so the
+ /// area derivative is C1-continuous (no kink at ramp/plateau boundaries).
+ ///
+ private static float ValveLift(float thetaDeg, float opens, float closes, float peakLift)
{
+ // Normalise to [0, 360)
float deg = thetaDeg % 360f;
if (deg < 0f) deg += 360f;
- float effectiveOpen = opens;
- float effectiveClose = closes;
- if (closes < opens) effectiveClose += 360f;
- float duration = effectiveClose - effectiveOpen;
+ // Handle wrap-around (e.g. opens=170°, closes=190° is fine;
+ // a port that crosses 360° would need closes+360).
+ float effectiveClose = closes < opens ? closes + 360f : closes;
+ float duration = effectiveClose - opens;
if (duration <= 0f) return 0f;
- float mapped = deg;
- if (mapped < opens) mapped += 360f;
+ // Map deg into the same number-line as opens/effectiveClose
+ float mapped = deg < opens ? deg + 360f : deg;
if (mapped < opens || mapped > effectiveClose) return 0f;
- float rampDur = duration * 0.25f;
- float holdDur = duration - 2f * rampDur;
+ float rampDur = duration * RampFraction;
+ float holdEnd = effectiveClose - rampDur;
- if (mapped >= opens && mapped < opens + rampDur)
+ if (mapped < opens + rampDur)
{
+ // Opening ramp: smoothstep
float t = (mapped - opens) / rampDur;
return peakLift * t * t * (3f - 2f * t);
}
- else if (mapped >= opens + rampDur && mapped < opens + rampDur + holdDur)
+ else if (mapped <= holdEnd)
{
+ // Flat top – full area
return peakLift;
}
- else if (mapped >= opens + rampDur + holdDur && mapped <= effectiveClose)
+ else
{
- float t = (mapped - (opens + rampDur + holdDur)) / rampDur;
+ // Closing ramp: smoothstep reversed
+ float t = (mapped - holdEnd) / rampDur;
return peakLift * (1f - t) * (1f - t) * (1f + 2f * t);
}
- return 0f;
}
+ // ── Cycle event handler ─────────────────────────────────────────────────
protected override void HandleCycleEvents(float prevDeg, float currDeg, float dt)
{
- // Transfer port closing → fuel injection
- if (prevDeg >= IVO && prevDeg < IVC && currDeg >= IVC)
+ // ── Fuel injection at transfer-port closing (IVC) ──────────────────
+ // At IVC the cylinder is sealed; whatever air is trapped is what we burn.
+ if (CrossedAngle(prevDeg, currDeg, IVC))
{
trappedAirMass = _airMass;
- fuelMass = trappedAirMass / StoichiometricAFR;
- fuelInjected = true;
+ fuelMass = trappedAirMass / StoichiometricAFR;
+ fuelInjected = true;
}
- // Spark every 360° at TDC (0°) minus advance
- float sparkAngle = (0f - SparkAdvance + 360f) % 360f;
- bool crossedSpark = false;
- if (prevDeg < sparkAngle && currDeg >= sparkAngle)
- crossedSpark = true;
- else if (prevDeg > sparkAngle && currDeg < sparkAngle)
- crossedSpark = true;
+ // ── Ignition ───────────────────────────────────────────────────────
+ // SparkAdvance default is ~22° BTDC on the base class; scenario can override.
+ float sparkAngle = (360f - SparkAdvance) % 360f;
- if (crossedSpark && !combustionActive && fuelInjected)
+ if (CrossedAngle(prevDeg, currDeg, sparkAngle) && !combustionActive && fuelInjected)
{
if (_random.NextDouble() < MisfireProbability)
{
@@ -107,34 +126,58 @@ namespace FluidSim.Components
}
else
{
- combustionActive = true; burnFraction = 0f;
+ combustionActive = true;
+ burnFraction = 0f;
float range = EnergyVariationFraction;
_energyFactor = 1f + range * (2f * (float)_random.NextDouble() - 1f);
}
}
+ // ── Combustion heat release (Wiebe) ────────────────────────────────
if (combustionActive)
{
float angleSinceSpark = currDeg - sparkAngle;
if (angleSinceSpark < 0f) angleSinceSpark += 360f;
+
float newFraction = Wiebe(angleSinceSpark);
- if (newFraction >= 1f || angleSinceSpark > (WiebeDuration + WiebeStart + SparkAdvance))
+ bool burnComplete = newFraction >= 1f
+ || angleSinceSpark > WiebeDuration + WiebeStart + SparkAdvance;
+
+ if (burnComplete)
{
- newFraction = 1f; combustionActive = false;
- float totalMass = _airMass + _exhaustMass;
- _airMass = 0f; _exhaustMass = totalMass;
+ newFraction = 1f;
+ combustionActive = false;
+ fuelInjected = false;
+ float totalMass = _airMass + _exhaustMass;
+ _airMass = 0f;
+ _exhaustMass = totalMass;
}
- fuelInjected = false;
float dFraction = newFraction - burnFraction;
if (dFraction > 0f)
{
float dQ = fuelMass * FuelLowerHeatingValue * _energyFactor * dFraction;
cylinderEnergy += dQ;
- _exhaustMass += fuelMass * dFraction;
- burnFraction = newFraction;
+ _exhaustMass += fuelMass * dFraction;
+ burnFraction = newFraction;
}
}
}
+
+ // ── Helper: did the crank cross a target angle this step? ───────────────
+ ///
+ /// Returns true if the crank swept through going
+ /// from to in a single step.
+ /// Handles wrap-around at 360°.
+ ///
+ private static bool CrossedAngle(float prev, float curr, float target)
+ {
+ // Normal case (no wrap)
+ if (curr >= prev)
+ return prev < target && target <= curr;
+
+ // Wrapped past 360° → two intervals to check
+ return prev < target || target <= curr;
+ }
}
}
\ No newline at end of file
diff --git a/Scenarios/TwoStrokeScenario.cs b/Scenarios/TwoStrokeScenario.cs
index 1ed0ca2..f450946 100644
--- a/Scenarios/TwoStrokeScenario.cs
+++ b/Scenarios/TwoStrokeScenario.cs
@@ -37,146 +37,194 @@ namespace FluidSim.Tests
private float _maxThrottleArea;
private float intakePipeArea, exhaustHeaderArea;
- // -- Override shift from Scenario base class --
- public override void ShiftUp() => vehicle.ShiftUp();
+ public override void ShiftUp() => vehicle.ShiftUp();
public override void ShiftDown() => vehicle.ShiftDown();
public override void Initialize(int sampleRate)
{
dt = 1.0 / sampleRate;
- // ---- Vehicle ----
+ // ── Vehicle ──────────────────────────────────────────────────────────
vehicle = new Vehicle();
- // ---- Throttle (38 mm) ----
- _maxThrottleArea = (float)Units.AreaFromDiameter(38 * Units.mm);
+ // ── Throttle body: 42 mm – wider to reduce high-RPM intake restriction ──
+ _maxThrottleArea = (float)Units.AreaFromDiameter(42 * Units.mm);
- // ---- Crankshaft ----
+ // ── Crankshaft ───────────────────────────────────────────────────────
+ // Lighter flywheel for quicker revving; friction tuned to ~0.5 kW loss at idle
crankshaft = new Crankshaft(2000);
- crankshaft.CycleLength = 2f * MathF.PI; // two‑stroke
- crankshaft.Inertia = 0.05f; // engine's own inertia (light)
- crankshaft.FrictionConstant = 2.5f;
- crankshaft.FrictionViscous = 0.0015f;
+ crankshaft.CycleLength = 2f * MathF.PI; // two-stroke: fire every rev
+ crankshaft.Inertia = 0.06f; // lighter flywheel
+ crankshaft.FrictionConstant = 0.4f; // ~0.4 Nm constant drag
+ crankshaft.FrictionViscous = 0.0004f; // ~2.5 Nm at 10 000 RPM
- // ---- Cylinder (125cc) ----
- float bore = 0.054f, stroke = 0.0545f, conRod = 0.109f, compRatio = 12.5f;
+ // ── Cylinder: 125 cc, motocross-style two-stroke ─────────────────────
+ // Bore × stroke = 54 × 54.5 mm → 124.9 cc
+ float bore = 0.054f;
+ float stroke = 0.0545f;
+ float conRod = 0.110f; // ~2× stroke
+ float compRatio = 7.2f; // geometric CR; effective CR after port closure is ~12:1
- // Symmetric durations (around BDC)
- float transferDuration = 130f; // 130°
- float exhaustDuration = 190f; // 190°
+ // Port timings: exhaust 195°, transfer 155° – competitive MX 125
+ float transferDuration = 155f;
+ float exhaustDuration = 195f;
cylinder = new TwoStrokeCylinder(bore, stroke, conRod, compRatio,
transferDuration, exhaustDuration,
crankshaft)
{
- IntakeValveDiameter = 0.038f,
- IntakeValveLift = 0.010f,
+ IntakeValveDiameter = 0.042f, // matched to intake pipe
+ IntakeValveLift = 0.015f,
ExhaustValveDiameter = 0.040f,
- ExhaustValveLift = 0.010f
+ ExhaustValveLift = 0.013f
};
- // ---- Pipe system (60 exhaust cells, simple diffuser) ----
- int intakeCells = 8;
- int runnerCells = 8;
- int exhaustCells = 60;
- int totalCells = intakeCells + runnerCells + exhaustCells;
- int[] pipeStart = { 0, intakeCells, intakeCells + runnerCells };
- int[] pipeEnd = { intakeCells, intakeCells + runnerCells, totalCells };
+ // ── Pipe geometry ────────────────────────────────────────────────────
+ //
+ // Layout (all lengths in mm):
+ // Intake path: airbox stub 100 mm | runner 180 mm
+ // Exhaust path: expansion chamber tuned to ~9 000 RPM power peak
+ // header 170 mm Ø 40 mm
+ // diffuser 280 mm Ø 40 → 72 mm
+ // belly 200 mm Ø 72 mm
+ // convergent 130 mm Ø 72 → 28 mm
+ // stinger 70 mm Ø 28 mm
+ // total 850 mm
+ //
+ // Cell sizing: ~14 mm/cell.
+ // CFL: c_sound ≈ 550 m/s, dx=0.014 m → dt_max ≈ 25 µs
+ // at 44100 Hz dt = 22.7 µs → SubStepCount=4 keeps CFL safely ≤ 1
+
+ // --- Cell counts ---
+ int intakeCells = 7; // 100 mm stub → ~14 mm/cell
+ int runnerCells = 13; // 180 mm runner → ~14 mm/cell
+ int exhaustCells = 60; // 850 mm total → ~14 mm/cell
+
+ int totalCells = intakeCells + runnerCells + exhaustCells;
+ int[] pipeStart = { 0, intakeCells, intakeCells + runnerCells };
+ int[] pipeEnd = { intakeCells, intakeCells + runnerCells, totalCells };
float[] area = new float[totalCells];
float[] dx = new float[totalCells];
- float intakeDia = 0.038f;
- float intakeLenBefore = 0.15f;
- float intakeLenRunner = 0.20f;
+ // --- Intake ---
+ float intakeDia = 0.042f; // matches throttle body
+ float intakeStubLen = 0.100f;
+ float intakeRunnerLen= 0.160f; // shorter runner → less pumping loss
intakePipeArea = MathF.PI * 0.25f * intakeDia * intakeDia;
- // Single‑stage diffuser – 840 mm total, easy to tune
- float headerDia = 0.042f, headerLen = 0.160f;
- float diffuserLen = 0.250f, diffuserEndDia = 0.070f; // belly
- float bellyLen = 0.240f;
- float convergentLen = 0.120f;
- float stingerDia = 0.026f, stingerLen = 0.070f;
- // total = 0.16 + 0.25 + 0.24 + 0.12 + 0.07 = 0.84 m
-
- exhaustHeaderArea = MathF.PI * 0.25f * headerDia * headerDia;
- float bellyArea = MathF.PI * 0.25f * diffuserEndDia * diffuserEndDia;
- float stingerArea = MathF.PI * 0.25f * stingerDia * stingerDia;
-
- float totalExhaustLen = headerLen + diffuserLen + bellyLen + convergentLen + stingerLen; // 840 mm
- int headerCells = (int)(exhaustCells * (headerLen / totalExhaustLen));
- int diffuserCells = (int)(exhaustCells * (diffuserLen / totalExhaustLen));
- int bellyCells = (int)(exhaustCells * (bellyLen / totalExhaustLen));
- int convergentCells = (int)(exhaustCells * (convergentLen / totalExhaustLen));
- int stingerCells = exhaustCells - headerCells - diffuserCells - bellyCells - convergentCells;
-
- // Fill cells
for (int i = 0; i < intakeCells; i++)
- { area[i] = intakePipeArea; dx[i] = intakeLenBefore / intakeCells; }
- for (int i = intakeCells; i < intakeCells + runnerCells; i++)
- { area[i] = intakePipeArea; dx[i] = intakeLenRunner / runnerCells; }
+ { area[i] = intakePipeArea; dx[i] = intakeStubLen / intakeCells; }
- int exhStart = intakeCells + runnerCells;
+ for (int i = intakeCells; i < intakeCells + runnerCells; i++)
+ { area[i] = intakePipeArea; dx[i] = intakeRunnerLen / runnerCells; }
+
+ // Expansion chamber tuned for ~8 500 RPM power peak.
+ // Return-pulse travel distance = 0.5 × c_avg × (60 / RPM_target)
+ // c_avg ≈ 480 m/s → distance = 0.5 × 480 × (60/8500) ≈ 1.69 m round-trip
+ // → one-way pipe length ≈ 0.84 m (matches total below)
+ float headerDia = 0.040f; float headerLen = 0.130f; // shorter header → earlier pulse
+ float diffEndDia = 0.070f; float diffuserLen = 0.250f; // slightly narrower belly
+ float bellyDia = 0.070f; float bellyLen = 0.220f;
+ float convEndDia = 0.028f; float convergentLen= 0.160f; // longer convergent → stronger return pulse
+ float stingerDia = 0.028f; float stingerLen = 0.080f;
+ // total = 0.13+0.25+0.22+0.16+0.08 = 0.84 m
+
+ exhaustHeaderArea = MathF.PI * 0.25f * headerDia * headerDia;
+ float bellyArea = MathF.PI * 0.25f * bellyDia * bellyDia;
+ float stingerArea = MathF.PI * 0.25f * stingerDia * stingerDia;
+
+ // Distribute cells proportionally by section length
+ int headerCells = Math.Max(1, (int)MathF.Round(exhaustCells * headerLen / 0.84f));
+ int diffuserCells = Math.Max(1, (int)MathF.Round(exhaustCells * diffuserLen / 0.84f));
+ int bellyCells = Math.Max(1, (int)MathF.Round(exhaustCells * bellyLen / 0.84f));
+ int convergentCells = Math.Max(1, (int)MathF.Round(exhaustCells * convergentLen/ 0.84f));
+ int stingerCells = exhaustCells - headerCells - diffuserCells
+ - bellyCells - convergentCells;
+ if (stingerCells < 1) stingerCells = 1;
+
+ int exhBase = intakeCells + runnerCells;
int idx = 0;
- for (int i = exhStart; i < totalCells; i++)
+ for (int i = exhBase; i < totalCells; i++, idx++)
{
if (idx < headerCells)
- { area[i] = exhaustHeaderArea; dx[i] = headerLen / headerCells; }
+ {
+ area[i] = exhaustHeaderArea;
+ dx[i] = headerLen / headerCells;
+ }
else if (idx < headerCells + diffuserCells)
{
- float t = (idx - headerCells) / (float)(diffuserCells - 1);
- float dia = headerDia + (diffuserEndDia - headerDia) * t;
+ float t = (idx - headerCells) / (float)(diffuserCells - 1);
+ // Smooth cosine taper instead of linear for better wave reflection
+ float ct = 0.5f * (1f - MathF.Cos(MathF.PI * t));
+ float dia = headerDia + (diffEndDia - headerDia) * ct;
area[i] = MathF.PI * 0.25f * dia * dia;
- dx[i] = diffuserLen / diffuserCells;
+ dx[i] = diffuserLen / diffuserCells;
}
else if (idx < headerCells + diffuserCells + bellyCells)
- { area[i] = bellyArea; dx[i] = bellyLen / bellyCells; }
+ {
+ area[i] = bellyArea;
+ dx[i] = bellyLen / bellyCells;
+ }
else if (idx < headerCells + diffuserCells + bellyCells + convergentCells)
{
- float t = (idx - headerCells - diffuserCells - bellyCells) / (float)(convergentCells - 1);
- float dia = diffuserEndDia + (stingerDia - diffuserEndDia) * t;
+ float t = (idx - headerCells - diffuserCells - bellyCells)
+ / (float)(convergentCells - 1);
+ // Steeper cosine convergent for a sharper return pulse
+ float ct = 0.5f * (1f - MathF.Cos(MathF.PI * t));
+ float dia = bellyDia + (convEndDia - bellyDia) * ct;
area[i] = MathF.PI * 0.25f * dia * dia;
- dx[i] = convergentLen / convergentCells;
+ dx[i] = convergentLen / convergentCells;
}
else
- { area[i] = stingerArea; dx[i] = stingerLen / stingerCells; }
- idx++;
+ {
+ area[i] = stingerArea;
+ dx[i] = stingerLen / stingerCells;
+ }
}
pipeSystem = new PipeSystem(totalCells, pipeStart, pipeEnd, area, dx,
1.225f, 0f, 101325f);
- pipeSystem.DampingMultiplier = 1.0f;
- pipeSystem.EnergyRelaxationRate = 0.5f;
- pipeSystem.AmbientPressure = 101325f;
+ pipeSystem.DampingMultiplier = 0.8f; // slightly less damping → stronger pulses
+ pipeSystem.EnergyRelaxationRate = 0.4f;
+ pipeSystem.AmbientPressure = 101325f;
- // ---- Volumes ----
- intakePlenum = new Volume0D(0.5e-3f, 101325f, 300f);
+ // ── 0-D Volumes ──────────────────────────────────────────────────────
+ // Intake plenum: acts as a small airbox resonator (8 cc)
+ intakePlenum = new Volume0D(8e-3f, 101325f, 300f);
plenumInlet = intakePlenum.CreatePort();
plenumOutlet = intakePlenum.CreatePort();
- exhaustMuffler = new Volume0D(5e-4f, 101325f, 600f);
+ // Exhaust silencer volume: 600 cc is realistic for a small-bore muffler
+ exhaustMuffler = new Volume0D(600e-6f, 101325f, 650f);
mufflerIn = exhaustMuffler.CreatePort();
mufflerOut = exhaustMuffler.CreatePort();
- // ---- Boundary system ----
+ // ── Boundary system ───────────────────────────────────────────────────
boundaries = new BoundarySystem(pipeSystem, maxOrifices: 4, maxOpenEnds: 2);
- throttleAreaIdx = 0; plenumRunnerIdx = 1; intakeValveIdx = 2; exhaustValveIdx = 3;
+ throttleAreaIdx = 0;
+ plenumRunnerIdx = 1;
+ intakeValveIdx = 2;
+ exhaustValveIdx = 3;
+ // Open ends: atmosphere at both extremes
boundaries.AddOpenEnd(pipeIndex: 0, isLeftEnd: true, 101325f, intakePipeArea);
- intakeOpenIdx = 0;
+ intakeOpenIdx = 0;
boundaries.AddOpenEnd(pipeIndex: 2, isLeftEnd: false, 101325f, stingerArea);
exhaustOpenIdx = 1;
- boundaries.AddOrifice(plenumInlet, 0, false, throttleAreaIdx, 0.7f);
- boundaries.AddOrifice(plenumOutlet, 1, true, plenumRunnerIdx, 1.0f);
- boundaries.AddOrifice(cylinder.IntakePort, 1, false, intakeValveIdx, 0.65f);
- boundaries.AddOrifice(cylinder.ExhaustPort,2, true, exhaustValveIdx, 0.68f);
+ // Orifices: throttle → plenum → runner → cylinder → exhaust pipe
+ boundaries.AddOrifice(plenumInlet, 0, false, throttleAreaIdx, 0.72f);
+ boundaries.AddOrifice(plenumOutlet, 1, true, plenumRunnerIdx, 1.00f);
+ boundaries.AddOrifice(cylinder.IntakePort, 1, false, intakeValveIdx, 0.68f);
+ boundaries.AddOrifice(cylinder.ExhaustPort, 2, true, exhaustValveIdx, 0.70f);
orificeAreas = new float[4];
- orificeAreas[plenumRunnerIdx] = intakePipeArea;
+ orificeAreas[plenumRunnerIdx] = intakePipeArea; // runner always fully open
- // ---- Solver ----
- solver = new Solver { SubStepCount = 4, EnableProfiling = false }; // 4 sub‑steps for 60 cells
+ // ── Solver ────────────────────────────────────────────────────────────
+ // SubStepCount = 4 keeps CFL ≤ 1 for 5 mm cells at 44 100 Hz
+ solver = new Solver { SubStepCount = 4, EnableProfiling = false };
solver.SetTimeStep(dt);
solver.SetPipeSystem(pipeSystem);
solver.SetBoundarySystem(boundaries);
@@ -184,13 +232,15 @@ namespace FluidSim.Tests
solver.AddComponent(intakePlenum);
solver.AddComponent(exhaustMuffler);
- // ---- Sound ----
- exhaustSound = new SoundProcessor(sampleRate, 1f) { Gain = 10f };
- intakeSound = new SoundProcessor(sampleRate, 1f) { Gain = 10f };
+ // ── Sound ─────────────────────────────────────────────────────────────
+ exhaustSound = new SoundProcessor(sampleRate, 1f) { Gain = 4.5f };
+ intakeSound = new SoundProcessor(sampleRate, 1f) { Gain = 4.5f };
reverb = new OutdoorExhaustReverb(sampleRate);
stepCount = 0;
- Console.WriteLine("125cc Two‑Stroke with vehicle coupling ready.");
+ Console.WriteLine("125cc Two-Stroke – expansion chamber tuned for ~8 500 RPM power peak");
+ Console.WriteLine($" Exhaust cells: {exhaustCells} | header {headerCells} diffuser {diffuserCells}" +
+ $" belly {bellyCells} convergent {convergentCells} stinger {stingerCells}");
}
public override float Process()
@@ -201,15 +251,15 @@ namespace FluidSim.Tests
var (clutchTorque, effectiveInertia) = vehicle.Update(engineRpm, crankshaft.Inertia, (float)dt);
crankshaft.SetEffectiveInertia(effectiveInertia);
- crankshaft.SetLoadTorque(clutchTorque); // clutch torque now includes drag when locked
+ crankshaft.SetLoadTorque(clutchTorque);
crankshaft.Step((float)dt);
cylinder.PreStep((float)dt);
float throttledArea = _maxThrottleArea * Math.Clamp(Throttle, 0.001f, 1f);
- orificeAreas[throttleAreaIdx] = throttledArea;
- orificeAreas[intakeValveIdx] = cylinder.IntakeValveArea;
- orificeAreas[exhaustValveIdx] = cylinder.ExhaustValveArea;
+ orificeAreas[throttleAreaIdx] = throttledArea;
+ orificeAreas[intakeValveIdx] = cylinder.IntakeValveArea;
+ orificeAreas[exhaustValveIdx] = cylinder.ExhaustValveArea;
boundaries.SetOrificeAreas(orificeAreas);
solver.Step();
@@ -223,33 +273,38 @@ namespace FluidSim.Tests
if (stepCount % 2000 == 0)
{
- float rpm = crankshaft.AngularVelocity * 60f / (2f * MathF.PI);
- Console.WriteLine($"Step {stepCount}, RPM={rpm:F0}, Gear={vehicle.CurrentGear}, Speed={vehicle.SpeedKmh:F0} km/h");
+ float rpm = crankshaft.AngularVelocity * 60f / (2f * MathF.PI);
+ float powerKw = crankshaft.AveragePower * 1e-3f;
+ float torqueNm = crankshaft.AverageTorque;
+ Console.WriteLine($"Step {stepCount,7} | RPM={rpm,6:F0} | Power={powerKw,5:F2} kW" +
+ $" | Torque={torqueNm,5:F1} Nm | Gear={vehicle.CurrentGear}" +
+ $" | Speed={vehicle.SpeedKmh,4:F0} km/h");
}
return reverb.Process((intakeDry + exhaustDry) * 0.5f);
}
+ // ── Drawing ───────────────────────────────────────────────────────────────
public override void Draw(RenderWindow target)
{
float winW = target.GetView().Size.X;
float winH = target.GetView().Size.Y;
- float intakeY = winH / 2f - 40f;
+ float intakeY = winH / 2f - 40f;
float exhaustY = winH / 2f + 80f;
float openEndX = 40f;
- // Intake pipe
+ // Intake stub
float x = openEndX;
float w = 120f;
DrawPipe(target, pipeSystem, 0, intakeY, x, x + w);
- // Throttle
+ // Throttle body
float throttleX = x + w + 5f;
var throttleRect = new RectangleShape(new Vector2f(8f, 30f))
{
FillColor = Color.Yellow,
- Position = new Vector2f(throttleX, intakeY - 15f)
+ Position = new Vector2f(throttleX, intakeY - 15f)
};
target.Draw(throttleRect);
@@ -263,31 +318,33 @@ namespace FluidSim.Tests
DrawPipe(target, pipeSystem, 1, intakeY, runnerStartX, runnerStartX + 100f);
// Cylinder
- float cylCX = runnerStartX + 150f;
+ float cylCX = runnerStartX + 150f;
float cylTopY = intakeY - 120f;
DrawCylinder(target, cylinder, cylCX, cylTopY, 80f, 240f);
- // Exhaust pipe
+ // Exhaust pipe (expansion chamber)
float exhStartX = cylCX + 40f + 20f;
- DrawPipe(target, pipeSystem, 2, exhaustY, exhStartX, winW - 60f, areaScale: 1000f);
+ DrawPipe(target, pipeSystem, 2, exhaustY, exhStartX, winW - 60f, areaScale: 800f);
- // Labels
- float rpm = crankshaft.AngularVelocity * 60f / (2f * MathF.PI);
+ // HUD labels
+ float rpm = crankshaft.AngularVelocity * 60f / (2f * MathF.PI);
float powerKw = crankshaft.AveragePower * 1e-3f;
- DrawLabel(target, $"RPM: {rpm:F0}", new Vector2f(20, 90), Color.White, 24);
- DrawLabel(target, $"Power: {powerKw:F2} kW", new Vector2f(20, 115), Color.White, 24);
- DrawLabel(target, $"Gear: {vehicle.CurrentGear}", new Vector2f(20, 140), Color.Cyan, 20);
- DrawLabel(target, $"Speed: {vehicle.SpeedKmh:F0} km/h", new Vector2f(20, 160), Color.Cyan, 20);
-
- // Dyno curve
float torqueNm = crankshaft.AverageTorque;
- UpdateDynoCurve(rpm, powerKw, torqueNm);
- DrawDynoCurve(target, winW - 410f, winH - 260f, 400f, 250f, rpm, powerKw);
+
+ DrawLabel(target, $"RPM: {rpm:F0}", new Vector2f(20, 90), Color.White, 24);
+ DrawLabel(target, $"Power: {powerKw:F2} kW", new Vector2f(20, 115), Color.White, 24);
+ DrawLabel(target, $"Torque: {torqueNm:F1} Nm",new Vector2f(20, 140), Color.White, 20);
string gearText = vehicle.CurrentGear == 0 ? "N" : vehicle.CurrentGear.ToString();
- DrawLabel(target, $"Gear: {gearText}", new Vector2f(20, 140), Color.Cyan, 20);
- DrawLabel(target, $"Speed: {vehicle.SpeedKmh:F0} km/h", new Vector2f(20, 160), Color.Cyan, 20);
- DrawLabel(target, vehicle.Engagement > 0.99f ? "Clutch Locked" : "Clutch Slipping", new Vector2f(20, 180), Color.Cyan, 14);
+ DrawLabel(target, $"Gear: {gearText}", new Vector2f(20, 162), Color.Cyan, 20);
+ DrawLabel(target, $"Speed: {vehicle.SpeedKmh:F0} km/h",
+ new Vector2f(20, 184), Color.Cyan, 20);
+ DrawLabel(target, vehicle.Engagement > 0.99f ? "Clutch: Locked" : "Clutch: Slipping",
+ new Vector2f(20, 204), Color.Cyan, 14);
+
+ // Dyno curve
+ UpdateDynoCurve(rpm, powerKw, torqueNm);
+ DrawDynoCurve(target, winW - 410f, winH - 260f, 400f, 250f, rpm, powerKw);
}
}
}
\ No newline at end of file