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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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2
Core/OrificeBoundary.cs
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@@ -1,5 +1,5 @@
using System;
using FluidSim.Components;
using FluidSim.Interfaces;
namespace FluidSim.Core
{

75
Core/Simulation.cs
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@@ -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
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@@ -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
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@@ -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;
}
}
}