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Added boundary states for correct resonances

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max
2026-05-03 01:52:55 +02:00
parent 3926ed7ef9
commit a006a07049
9 changed files with 432 additions and 244 deletions
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379
Components/Pipe1D.cs
View File

@@ -3,24 +3,35 @@ using FluidSim.Interfaces;
namespace FluidSim.Components
{
public enum BoundaryType
{
VolumeCoupling,
OpenEnd,
ClosedEnd
}
public class Pipe1D
{
public Port PortA { get; }
public Port PortB { get; }
public double Area => _area;
private int _n; // number of cells
private int _n;
private double _dx, _dt, _gamma, _area;
private double[] _rho, _rhou, _E;
// Volume boundary states, constant during sub‑steps
private double _rhoLeft, _pLeft;
private double _rhoRight, _pRight;
private bool _leftBCSet, _rightBCSet;
// CFL control
private BoundaryType _leftBCType = BoundaryType.VolumeCoupling;
private BoundaryType _rightBCType = BoundaryType.VolumeCoupling;
private double _leftAmbientPressure = 101325.0;
private double _rightAmbientPressure = 101325.0;
private const double CflTarget = 0.8;
private const double ReferenceSoundSpeed = 340.0; // m/s, standard air
private const double ReferenceSoundSpeed = 340.0;
public double FrictionFactor { get; set; } = 0.02;
@@ -29,28 +40,29 @@ namespace FluidSim.Components
public double GetCellPressure(int i) => Pressure(i);
public double GetCellVelocity(int i) => _rhou[i] / Math.Max(_rho[i], 1e-12);
/// <summary>
/// Creates a 1D pipe.
/// Cell count is automatically determined to satisfy CFL in still air.
/// </summary>
/// <param name="length">Pipe length in metres.</param>
/// <param name="area">Cross‑sectional area in m².</param>
/// <param name="sampleRate">Global simulation sample rate (Hz).</param>
public Pipe1D(double length, double area, int sampleRate)
{
// Desired spatial step to keep CFL ≤ target for still air
double dtGlobal = 1.0 / sampleRate;
double dxTarget = ReferenceSoundSpeed * dtGlobal * CflTarget;
public BoundaryType LeftBCType => _leftBCType;
public BoundaryType RightBCType => _rightBCType;
// Number of cells must be at least 2; try to hit dxTarget
int nCells = Math.Max(2, (int)Math.Round(length / dxTarget, MidpointRounding.AwayFromZero));
// Ensure we don't accidentally overshoot dxTarget by more than a factor
while (length / nCells > dxTarget * 1.01 && nCells < int.MaxValue - 1)
nCells++;
public Pipe1D(double length, double area, int sampleRate, int forcedCellCount = 0)
{
double dtGlobal = 1.0 / sampleRate;
int nCells;
if (forcedCellCount > 1)
{
nCells = forcedCellCount;
}
else
{
double dxTarget = ReferenceSoundSpeed * dtGlobal * CflTarget;
nCells = Math.Max(2, (int)Math.Round(length / dxTarget, MidpointRounding.AwayFromZero));
while (length / nCells > dxTarget * 1.01 && nCells < int.MaxValue - 1)
nCells++;
}
_n = nCells;
_dx = length / _n;
_dt = dtGlobal; // global (audio) time step
_dt = dtGlobal;
_area = area;
_gamma = 1.4;
@@ -62,6 +74,11 @@ namespace FluidSim.Components
PortB = new Port();
}
public void SetLeftBoundaryType(BoundaryType type) => _leftBCType = type;
public void SetRightBoundaryType(BoundaryType type) => _rightBCType = type;
public void SetLeftAmbientPressure(double p) => _leftAmbientPressure = p;
public void SetRightAmbientPressure(double p) => _rightAmbientPressure = p;
public void SetUniformState(double rho, double u, double p)
{
double e = p / ((_gamma - 1) * rho);
@@ -74,10 +91,14 @@ namespace FluidSim.Components
}
}
public double GetLeftPressure() => Pressure(0);
public double GetRightPressure() => Pressure(_n - 1);
public double GetLeftDensity() => _rho[0];
public double GetRightDensity() => _rho[_n - 1];
public void SetCellState(int i, double rho, double u, double p)
{
if (i < 0 || i >= _n) return;
_rho[i] = rho;
_rhou[i] = rho * u;
double e = p / ((_gamma - 1) * rho);
_E[i] = rho * e + 0.5 * rho * u * u;
}
public void SetLeftVolumeState(double rhoVol, double pVol)
{
@@ -93,6 +114,165 @@ namespace FluidSim.Components
_rightBCSet = true;
}
public void ClearBC() => _leftBCSet = _rightBCSet = false;
public int GetRequiredSubSteps(double dtGlobal, double cflTarget = 0.8)
{
double maxW = 0.0;
for (int i = 0; i < _n; i++)
{
double rho = _rho[i];
double u = Math.Abs(_rhou[i] / Math.Max(rho, 1e-12));
double c = Math.Sqrt(_gamma * Pressure(i) / Math.Max(rho, 1e-12));
double local = u + c;
if (local > maxW) maxW = local;
}
maxW = Math.Max(maxW, 1e-8);
return Math.Max(1, (int)Math.Ceiling(dtGlobal * maxW / (cflTarget * _dx)));
}
public void SimulateSingleStep(double dtSub)
{
int n = _n;
double[] Fm = new double[n + 1];
double[] Fp = new double[n + 1];
double[] Fe = new double[n + 1];
// Left boundary (face 0)
switch (_leftBCType)
{
case BoundaryType.VolumeCoupling:
if (_leftBCSet)
{
HLLCFlux(_rhoLeft, 0.0, _pLeft,
_rho[0], _rhou[0] / Math.Max(_rho[0], 1e-12), Pressure(0),
out Fm[0], out Fp[0], out Fe[0]);
}
else
{
Fm[0] = 0; Fp[0] = Pressure(0); Fe[0] = 0;
}
break;
case BoundaryType.OpenEnd:
{
double rhoR = _rho[0];
double uR = _rhou[0] / Math.Max(rhoR, 1e-12);
double pR = Pressure(0);
HLLCFlux(rhoR, uR, _leftAmbientPressure,
rhoR, uR, pR,
out Fm[0], out Fp[0], out Fe[0]);
}
break;
case BoundaryType.ClosedEnd:
{
double rhoR = _rho[0];
double uR = _rhou[0] / Math.Max(rhoR, 1e-12);
double pR = Pressure(0);
HLLCFlux(rhoR, -uR, pR,
rhoR, uR, pR,
out Fm[0], out Fp[0], out Fe[0]);
}
break;
}
// Internal faces
for (int i = 0; i < n - 1; i++)
{
double uL = _rhou[i] / Math.Max(_rho[i], 1e-12);
double uR = _rhou[i + 1] / Math.Max(_rho[i + 1], 1e-12);
HLLCFlux(_rho[i], uL, Pressure(i),
_rho[i + 1], uR, Pressure(i + 1),
out Fm[i + 1], out Fp[i + 1], out Fe[i + 1]);
}
// Right boundary (face n)
switch (_rightBCType)
{
case BoundaryType.VolumeCoupling:
if (_rightBCSet)
{
double rhoL = _rho[n - 1];
double uL = _rhou[n - 1] / Math.Max(rhoL, 1e-12);
double pL = Pressure(n - 1);
HLLCFlux(rhoL, uL, pL,
_rhoRight, 0.0, _pRight,
out Fm[n], out Fp[n], out Fe[n]);
}
else
{
Fm[n] = 0; Fp[n] = Pressure(n - 1); Fe[n] = 0;
}
break;
case BoundaryType.OpenEnd:
{
double rhoL = _rho[n - 1];
double uL = _rhou[n - 1] / Math.Max(rhoL, 1e-12);
double pL = Pressure(n - 1);
HLLCFlux(rhoL, uL, pL,
rhoL, uL, _rightAmbientPressure,
out Fm[n], out Fp[n], out Fe[n]);
}
break;
case BoundaryType.ClosedEnd:
{
double rhoL = _rho[n - 1];
double uL = _rhou[n - 1] / Math.Max(rhoL, 1e-12);
double pL = Pressure(n - 1);
HLLCFlux(rhoL, uL, pL,
rhoL, -uL, pL,
out Fm[n], out Fp[n], out Fe[n]);
}
break;
}
// Cell update
for (int i = 0; i < n; i++)
{
double dM = (Fm[i + 1] - Fm[i]) / _dx;
double dP = (Fp[i + 1] - Fp[i]) / _dx;
double dE = (Fe[i + 1] - Fe[i]) / _dx;
_rho[i] -= dtSub * dM;
_rhou[i] -= dtSub * dP;
_E[i] -= dtSub * dE;
if (_rho[i] < 1e-12) _rho[i] = 1e-12;
double kinetic = 0.5 * _rhou[i] * _rhou[i] / _rho[i];
double pMin = 100.0;
double eMin = pMin / ((_gamma - 1) * _rho[i]) + kinetic;
if (_E[i] < eMin) _E[i] = eMin;
}
// Port quantities (only meaningful for volume coupled ends)
double mdotA_sub = _leftBCType == BoundaryType.VolumeCoupling && _leftBCSet ? Fm[0] * _area : 0.0;
double mdotB_sub = _rightBCType == BoundaryType.VolumeCoupling && _rightBCSet ? -Fm[n] * _area : 0.0;
PortA.MassFlowRate = mdotA_sub;
PortB.MassFlowRate = mdotB_sub;
PortA.Pressure = Pressure(0);
PortB.Pressure = Pressure(_n - 1);
PortA.Density = _rho[0];
PortB.Density = _rho[_n - 1];
if (_leftBCType == BoundaryType.VolumeCoupling && _leftBCSet)
{
PortA.SpecificEnthalpy = mdotA_sub < 0
? GetCellTotalSpecificEnthalpy(0)
: 0.0;
}
if (_rightBCType == BoundaryType.VolumeCoupling && _rightBCSet)
{
PortB.SpecificEnthalpy = mdotB_sub < 0
? GetCellTotalSpecificEnthalpy(_n - 1)
: 0.0;
}
}
private double GetCellTotalSpecificEnthalpy(int i)
{
double rho = Math.Max(_rho[i], 1e-12);
@@ -102,146 +282,6 @@ namespace FluidSim.Components
return h + 0.5 * u * u;
}
/// <summary>
/// Advance the pipe over one global time step using sub‑stepping.
/// Must be called once per global simulation cycle.
/// </summary>
public void Simulate()
{
int n = _n;
// --- Determine maximum wave speed in the pipe ---
double maxWaveSpeed = 0.0;
for (int i = 0; i < n; i++)
{
double rho = Math.Max(_rho[i], 1e-12);
double u = Math.Abs(_rhou[i] / rho);
double c = Math.Sqrt(_gamma * Pressure(i) / rho);
double local = u + c;
if (local > maxWaveSpeed) maxWaveSpeed = local;
}
if (maxWaveSpeed < 1e-8) maxWaveSpeed = 1e-8;
int nSub = Math.Max(1, (int)Math.Ceiling(_dt * maxWaveSpeed / (CflTarget * _dx)));
double dtSub = _dt / nSub;
// Accumulators for net mass flows
double sumMdotA = 0.0, sumMdotB = 0.0;
// Accumulators for fluid that ENTERS the volumes (pipe → volume)
double massInA = 0.0, energyInA = 0.0;
double massInB = 0.0, energyInB = 0.0;
for (int step = 0; step < nSub; step++)
{
double[] Fm = new double[n + 1];
double[] Fp = new double[n + 1];
double[] Fe = new double[n + 1];
// Left boundary (face 0)
if (_leftBCSet)
{
HLLCFlux(_rhoLeft, 0.0, _pLeft,
_rho[0], _rhou[0] / Math.Max(_rho[0], 1e-12), Pressure(0),
out Fm[0], out Fp[0], out Fe[0]);
}
else
{
Fm[0] = 0;
Fp[0] = Pressure(0);
Fe[0] = 0;
}
// Internal faces
for (int i = 0; i < n - 1; i++)
{
double uL = _rhou[i] / Math.Max(_rho[i], 1e-12);
double uR = _rhou[i + 1] / Math.Max(_rho[i + 1], 1e-12);
HLLCFlux(_rho[i], uL, Pressure(i),
_rho[i + 1], uR, Pressure(i + 1),
out Fm[i + 1], out Fp[i + 1], out Fe[i + 1]);
}
// Right boundary (face n)
if (_rightBCSet)
{
double rhoL = _rho[n - 1];
double uL = _rhou[n - 1] / Math.Max(rhoL, 1e-12);
double pL = Pressure(n - 1);
HLLCFlux(rhoL, uL, pL,
_rhoRight, 0.0, _pRight,
out Fm[n], out Fp[n], out Fe[n]);
}
else
{
Fm[n] = 0;
Fp[n] = Pressure(n - 1);
Fe[n] = 0;
}
// Cell update
for (int i = 0; i < n; i++)
{
double dM = (Fm[i + 1] - Fm[i]) / _dx;
double dP = (Fp[i + 1] - Fp[i]) / _dx;
double dE = (Fe[i + 1] - Fe[i]) / _dx;
_rho[i] -= dtSub * dM;
_rhou[i] -= dtSub * dP;
_E[i] -= dtSub * dE;
if (_rho[i] < 1e-12) _rho[i] = 1e-12;
double kinetic = 0.5 * _rhou[i] * _rhou[i] / _rho[i];
if (_E[i] < kinetic) _E[i] = kinetic;
}
// Sub‑step mass flow rates (kg/s)
double mdotA_sub = _leftBCSet ? Fm[0] * _area : 0.0; // >0 = into pipe
double mdotB_sub = _rightBCSet ? -Fm[n] * _area : 0.0; // >0 = into pipe from right
sumMdotA += mdotA_sub;
sumMdotB += mdotB_sub;
// Flow FROM pipe INTO volume A: mdotA_sub < 0
if (mdotA_sub < 0 && _leftBCSet)
{
double massRate = -mdotA_sub; // kg/s entering volume A
double h = GetCellTotalSpecificEnthalpy(0);
massInA += massRate * dtSub;
energyInA += massRate * dtSub * h;
}
// Flow FROM pipe INTO volume B: mdotB_sub < 0 (because
// mdotB_sub = -Fm[n], and Fm[n] > 0 is flow to the right)
if (mdotB_sub < 0 && _rightBCSet)
{
double massRate = -mdotB_sub; // kg/s entering volume B
double h = GetCellTotalSpecificEnthalpy(_n - 1);
massInB += massRate * dtSub;
energyInB += massRate * dtSub * h;
}
}
// Averaged net mass flows (sign: positive = into pipe)
PortA.MassFlowRate = sumMdotA / nSub;
PortB.MassFlowRate = sumMdotB / nSub;
// Assign enthalpy ONLY for the fluid that physically entered the volume
if (massInA > 1e-12)
PortA.SpecificEnthalpy = energyInA / massInA;
if (massInB > 1e-12)
PortB.SpecificEnthalpy = energyInB / massInB;
// If no inflow occurred, leave the port’s enthalpy unchanged.
// (It will be set to the volume’s static enthalpy by PushStateToPort
// or overwritten by TransferPipeToVolume if flow reverses later.)
_leftBCSet = _rightBCSet = false;
}
// Pressure and HLLC flux unchanged
private double Pressure(int i) =>
(_gamma - 1.0) * (_E[i] - 0.5 * _rhou[i] * _rhou[i] / Math.Max(_rho[i], 1e-12));
@@ -279,5 +319,12 @@ namespace FluidSim.Components
fm = rsR * Ss; fp = rsR * Ss * Ss + ps; fe = (rsR * EsR + ps) * Ss;
}
}
public double GetPressureAtFraction(double fraction)
{
int i = (int)(fraction * (_n - 1));
i = Math.Clamp(i, 0, _n - 1);
return Pressure(i);
}
}
}

17
Components/Volume0D.cs
View File

@@ -50,13 +50,26 @@ namespace FluidSim.Components
Port.SpecificEnthalpy = SpecificEnthalpy;
}
// Original integrate (uses the constructor’s sample rate)
public void Integrate()
{
Integrate(_dt);
}
public void SetPressure(double newPressure)
{
InternalEnergy = newPressure * Volume / (Gamma - 1.0);
// Mass stays the same, so density is unchanged
}
// New overload: integrate with a custom time step (for sub‑steps)
public void Integrate(double dtOverride)
{
double mdot = Port.MassFlowRate;
double h_in = Port.SpecificEnthalpy;
double dm = mdot * _dt;
double dE = (mdot * h_in) * _dt - Pressure * dVdt * _dt;
double dm = mdot * dtOverride;
double dE = (mdot * h_in) * dtOverride - Pressure * dVdt * dtOverride;
Mass += dm;
InternalEnergy += dE;

2
Core/OrificeBoundary.cs
View File

@@ -1,5 +1,5 @@
using System;
using FluidSim.Components;
using FluidSim.Interfaces;
namespace FluidSim.Core
{

75
Core/Simulation.cs
View File

@@ -1,5 +1,6 @@
using System;
using FluidSim.Components;
using FluidSim.Interfaces;
using FluidSim.Utils;
namespace FluidSim.Core
@@ -7,76 +8,64 @@ namespace FluidSim.Core
public static class Simulation
{
private static Solver solver;
private static Volume0D volA, volB;
private static Pipe1D pipe;
private static Connection connA, connB;
private static int stepCount;
private static double time;
private static double dt;
private static float sample;
private static double ambientPressure = 1.0 * Units.atm;
public static void Initialize(int sampleRate)
{
dt = 1.0 / sampleRate;
double V = 5.0 * Units.L;
volA = new Volume0D(V, 2.0 * Units.atm, Units.Celsius(20), sampleRate);
volB = new Volume0D(V, 1.0 * Units.atm, Units.Celsius(20), sampleRate);
double length = 0.2;
double radius = 5 * Units.mm;
double area = Units.AreaFromDiameter(radius);
double length = 150 * Units.mm;
double diameter = 25 * Units.mm;
double area = Units.AreaFromDiameter(25, Units.mm);
pipe = new Pipe1D(length, area, sampleRate);
pipe.SetUniformState(volA.Density, 0.0, volA.Pressure);
pipe.FrictionFactor = 0.02;
// Connections with orifice area equal to pipe area (flange joint)
connA = new Connection(volA.Port, pipe.PortA) { Area = area, DischargeCoefficient = 1.0, Gamma = 1.4 };
connB = new Connection(pipe.PortB, volB.Port) { Area = area, DischargeCoefficient = 1.0, Gamma = 1.4 };
pipe = new Pipe1D(length, area, sampleRate, forcedCellCount: 80);
pipe.SetUniformState(1.225, 0.0, ambientPressure);
pipe.FrictionFactor = 0.0;
solver = new Solver();
solver.AddVolume(volA);
solver.AddVolume(volB);
solver.SetTimeStep(dt);
solver.AddPipe(pipe);
solver.AddConnection(connA);
solver.AddConnection(connB);
solver.SetPipeBoundary(pipe, isLeft: true, BoundaryType.OpenEnd, ambientPressure);
solver.SetPipeBoundary(pipe, isLeft: false, BoundaryType.ClosedEnd);
// Excite the pipe with an initial pressure pulse near the open end
int pulseCells = 5;
double pulsePressure = 4 * ambientPressure;
for (int i = 0; i < pulseCells; i++)
pipe.SetCellState(i, 1.225, 0.0, pulsePressure);
}
public static float Process()
{
solver.Step();
sample = solver.Step();
time += dt;
stepCount++;
// Override the audio sample with mid-pipe pressure deviation
double pMid = pipe.GetPressureAtFraction(0.5);
sample = (float)((pMid - ambientPressure) / ambientPressure);
Log();
return 0f;
return sample;
}
public static void Log()
{
bool logPipe = true;
if ((stepCount <= 10 || (stepCount <= 1000 && stepCount % 100 == 0)) || stepCount % 1000 == 0 && stepCount < 10000)
if (stepCount % 10 == 0 && stepCount < 1000)
{
// Summary line
double pMid = pipe.GetPressureAtFraction(0.5);
double pOpen = pipe.GetCellPressure(0);
double pClosed = pipe.GetCellPressure(pipe.GetCellCount() - 1);
Console.WriteLine(
$"t = {time * 1e3:F3} ms Step {stepCount:D4}: " +
$"PA = {volA.Pressure / 1e5:F6} bar, " +
$"PB = {volB.Pressure / 1e5:F6} bar, " +
$"FlowA = {pipe.PortA.MassFlowRate * 1e3:F2} g/s");
// Per‑cell state
if (logPipe && stepCount <= 1000)
{
int n = pipe.GetCellCount();
for (int i = 0; i < n; i++)
{
double rho = pipe.GetCellDensity(i);
double p = pipe.GetCellPressure(i);
double u = pipe.GetCellVelocity(i);
Console.WriteLine(
$" Cell {i,2}: ρ={rho,8:F4} kg/m³, p={p,10:F2} Pa, u={u,8:F3} m/s");
}
}
$"Sample: = {sample:F3}, " +
$"P_mid = {pMid:F2} Pa ({pMid / ambientPressure:F4} atm), " +
$"P_open = {pOpen:F2} Pa, P_closed = {pClosed:F2} Pa");
}
}
}

143
Core/Solver.cs
View File

@@ -10,70 +10,163 @@ namespace FluidSim.Core
private readonly List<Pipe1D> _pipes = new();
private readonly List<Connection> _connections = new();
private double _dt; // global time step
public void AddVolume(Volume0D v) => _volumes.Add(v);
public void AddPipe(Pipe1D p) => _pipes.Add(p);
public void AddConnection(Connection c) => _connections.Add(c);
public void Step()
/// <summary>Set the global time step (called from Simulation).</summary>
public void SetTimeStep(double dt) => _dt = dt;
/// <summary>
/// Convenient method to set the boundary type of a pipe end.
/// </summary>
public void SetPipeBoundary(Pipe1D pipe, bool isLeft, BoundaryType type, double ambientPressure = 101325.0)
{
// 1. Volumes publish state to their ports
if (isLeft)
{
pipe.SetLeftBoundaryType(type);
if (type == BoundaryType.OpenEnd)
pipe.SetLeftAmbientPressure(ambientPressure);
}
else
{
pipe.SetRightBoundaryType(type);
if (type == BoundaryType.OpenEnd)
pipe.SetRightAmbientPressure(ambientPressure);
}
}
public float Step()
{
// 1. Volumes publish state to ports (only needed if any volume exists)
foreach (var v in _volumes)
v.PushStateToPort();
// 2. Set volume states as boundary conditions on pipes
// 2. Set initial pipe boundary conditions ONLY for volume‑coupled ends
foreach (var conn in _connections)
{
if (IsPipePort(conn.PortA) && IsVolumePort(conn.PortB))
SetVolumeBC(conn.PortA, conn.PortB);
{
var pipe = GetPipe(conn.PortA);
bool isLeft = pipe.PortA == conn.PortA;
BoundaryType bc = isLeft ? pipe.LeftBCType : pipe.RightBCType;
if (bc == BoundaryType.VolumeCoupling)
SetVolumeBC(conn.PortA, conn.PortB);
}
else if (IsVolumePort(conn.PortA) && IsPipePort(conn.PortB))
SetVolumeBC(conn.PortB, conn.PortA);
{
var pipe = GetPipe(conn.PortB);
bool isLeft = pipe.PortB == conn.PortB;
BoundaryType bc = isLeft ? pipe.LeftBCType : pipe.RightBCType;
if (bc == BoundaryType.VolumeCoupling)
SetVolumeBC(conn.PortB, conn.PortA);
}
}
// 3. Run pipe simulations
// 3. Determine number of sub‑steps
int nSub = 1;
foreach (var p in _pipes)
p.Simulate();
nSub = Math.Max(nSub, p.GetRequiredSubSteps(_dt));
double dtSub = _dt / nSub;
// 4. Transfer pipe‑port flows to volume ports
foreach (var conn in _connections)
// 4. Sub‑step loop
for (int sub = 0; sub < nSub; sub++)
{
if (IsPipePort(conn.PortA) && IsVolumePort(conn.PortB))
TransferPipeToVolume(conn.PortA, conn.PortB);
else if (IsVolumePort(conn.PortA) && IsPipePort(conn.PortB))
TransferPipeToVolume(conn.PortB, conn.PortA);
foreach (var p in _pipes)
p.SimulateSingleStep(dtSub);
// Transfer flows only for volume‑coupled connections
foreach (var conn in _connections)
{
if (IsPipePort(conn.PortA) && IsVolumePort(conn.PortB))
{
var pipe = GetPipe(conn.PortA);
bool isLeft = pipe.PortA == conn.PortA;
if (pipe.LeftBCType == BoundaryType.VolumeCoupling || pipe.RightBCType == BoundaryType.VolumeCoupling)
TransferAndIntegrate(conn.PortA, conn.PortB, dtSub);
}
else if (IsVolumePort(conn.PortA) && IsPipePort(conn.PortB))
{
var pipe = GetPipe(conn.PortB);
bool isLeft = pipe.PortB == conn.PortB;
if (pipe.LeftBCType == BoundaryType.VolumeCoupling || pipe.RightBCType == BoundaryType.VolumeCoupling)
TransferAndIntegrate(conn.PortB, conn.PortA, dtSub);
}
}
// Update BCs for volume‑coupled ends between sub‑steps
if (sub < nSub - 1)
{
foreach (var v in _volumes)
v.PushStateToPort();
foreach (var conn in _connections)
{
if (IsPipePort(conn.PortA) && IsVolumePort(conn.PortB))
{
var pipe = GetPipe(conn.PortA);
bool isLeft = pipe.PortA == conn.PortA;
if ((isLeft && pipe.LeftBCType == BoundaryType.VolumeCoupling) ||
(!isLeft && pipe.RightBCType == BoundaryType.VolumeCoupling))
SetVolumeBC(conn.PortA, conn.PortB);
}
else if (IsVolumePort(conn.PortA) && IsPipePort(conn.PortB))
{
var pipe = GetPipe(conn.PortB);
bool isLeft = pipe.PortB == conn.PortB;
if ((isLeft && pipe.LeftBCType == BoundaryType.VolumeCoupling) ||
(!isLeft && pipe.RightBCType == BoundaryType.VolumeCoupling))
SetVolumeBC(conn.PortB, conn.PortA);
}
}
}
}
// 5. Integrate volumes
foreach (var v in _volumes)
v.Integrate();
// 5. Audio samples from SoundConnections (if any)
var audioSamples = new List<float>();
foreach (var conn in _connections)
{
if (conn is SoundConnection sc)
audioSamples.Add(sc.GetAudioSample());
}
// 6. Clear volume BC flags
foreach (var p in _pipes)
p.ClearBC();
return SoundProcessor.MixAndClip(audioSamples.ToArray());
}
bool IsVolumePort(Port p) => _volumes.Exists(v => v.Port == p);
bool IsPipePort(Port p) => _pipes.Exists(pp => pp.PortA == p || pp.PortB == p);
Pipe1D GetPipe(Port p) => _pipes.Find(pp => pp.PortA == p || pp.PortB == p);
private bool IsVolumePort(Port p) => _volumes.Exists(v => v.Port == p);
private bool IsPipePort(Port p) => _pipes.Exists(pp => pp.PortA == p || pp.PortB == p);
private Pipe1D GetPipe(Port p) => _pipes.Find(pp => pp.PortA == p || pp.PortB == p);
private Volume0D GetVolume(Port p) => _volumes.Find(v => v.Port == p);
void SetVolumeBC(Port pipePort, Port volPort)
private void SetVolumeBC(Port pipePort, Port volPort)
{
Pipe1D pipe = GetPipe(pipePort);
var pipe = GetPipe(pipePort);
if (pipe == null) return;
bool isLeft = pipe.PortA == pipePort;
if (isLeft)
pipe.SetLeftVolumeState(volPort.Density, volPort.Pressure);
else
pipe.SetRightVolumeState(volPort.Density, volPort.Pressure);
}
void TransferPipeToVolume(Port pipePort, Port volPort)
private void TransferAndIntegrate(Port pipePort, Port volPort, double dtSub)
{
double mdot = pipePort.MassFlowRate;
volPort.MassFlowRate = -mdot;
if (mdot < 0) // pipe → volume
{
// pipePort.SpecificEnthalpy is already total (h + ½u²)
volPort.SpecificEnthalpy = pipePort.SpecificEnthalpy;
}
// else: volume → pipe, volume’s own static enthalpy is used (already set)
// else: volume’s own enthalpy (set by PushStateToPort) is used
GetVolume(volPort)?.Integrate(dtSub);
}
}
}

23
Core/SoundProcessor.cs Normal file
View File

@@ -0,0 +1,23 @@
namespace FluidSim.Core
{
/// <summary>
/// Mixes multiple audio samples and applies a soft‑clipping tanh.
/// </summary>
public static class SoundProcessor
{
/// <summary>Overall gain applied after mixing (before tanh).</summary>
public static float MasterGain { get; set; } = 0.01f;
/// <summary>
/// Mixes an array of raw audio samples and returns a single sample in [‑1, 1].
/// </summary>
public static float MixAndClip(params float[] samples)
{
float sum = 0f;
foreach (float s in samples)
sum += s;
sum *= MasterGain;
return sum;
}
}
}

4
Components/Connection.cs → Interfaces/Connection.cs
View File

@@ -1,6 +1,4 @@
using FluidSim.Interfaces;
namespace FluidSim.Components
namespace FluidSim.Interfaces
{
/// <summary>Pure data link between two ports, with orifice parameters.</summary>
public class Connection

25
Interfaces/SoundConnection.cs Normal file
View File

@@ -0,0 +1,25 @@
namespace FluidSim.Interfaces
{
/// <summary>
/// A Connection that also produces an audio sample from the pressure drop across it.
/// </summary>
public class SoundConnection : Connection
{
/// <summary>Gain applied to the normalised pressure difference.</summary>
public float Gain { get; set; } = 1.0f;
/// <summary>Reference pressure used for normalisation (Pa). Default: 1 atm.</summary>
public double ReferencePressure { get; set; } = 101325.0;
public SoundConnection(Port a, Port b) : base(a, b) { }
/// <summary>
/// Returns a normalised audio sample proportional to the pressure difference.
/// </summary>
public float GetAudioSample()
{
double dp = PortA.Pressure - PortB.Pressure;
return (float)(dp / ReferencePressure) * Gain;
}
}
}

8
Utils/Units.cs
View File

@@ -21,10 +21,10 @@ namespace FluidSim.Utils
public static double Celsius(double tC) => tC + 273.15;
public static double AreaFromRadius(double radius, double unit = mm) =>
Math.PI * (radius * unit) * (radius * unit);
public static double AreaFromRadius(double radius) =>
Math.PI * (radius) * (radius);
public static double AreaFromDiameter(double diameter, double unit = mm) =>
Math.PI * 0.25 * (diameter * unit) * (diameter * unit);
public static double AreaFromDiameter(double diameter) =>
Math.PI * 0.25 * (diameter) * (diameter);
}
}