330 lines
12 KiB
C#
330 lines
12 KiB
C#
using System;
|
|
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;
|
|
private double _dx, _dt, _gamma, _area;
|
|
private double[] _rho, _rhou, _E;
|
|
|
|
private double _rhoLeft, _pLeft;
|
|
private double _rhoRight, _pRight;
|
|
private bool _leftBCSet, _rightBCSet;
|
|
|
|
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;
|
|
|
|
public double FrictionFactor { get; set; } = 0.02;
|
|
|
|
public int GetCellCount() => _n;
|
|
public double GetCellDensity(int i) => _rho[i];
|
|
public double GetCellPressure(int i) => Pressure(i);
|
|
public double GetCellVelocity(int i) => _rhou[i] / Math.Max(_rho[i], 1e-12);
|
|
|
|
public BoundaryType LeftBCType => _leftBCType;
|
|
public BoundaryType RightBCType => _rightBCType;
|
|
|
|
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;
|
|
_area = area;
|
|
_gamma = 1.4;
|
|
|
|
_rho = new double[_n];
|
|
_rhou = new double[_n];
|
|
_E = new double[_n];
|
|
|
|
PortA = new Port();
|
|
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);
|
|
double Etot = rho * e + 0.5 * rho * u * u;
|
|
for (int i = 0; i < _n; i++)
|
|
{
|
|
_rho[i] = rho;
|
|
_rhou[i] = rho * u;
|
|
_E[i] = Etot;
|
|
}
|
|
}
|
|
|
|
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)
|
|
{
|
|
_rhoLeft = rhoVol;
|
|
_pLeft = pVol;
|
|
_leftBCSet = true;
|
|
}
|
|
|
|
public void SetRightVolumeState(double rhoVol, double pVol)
|
|
{
|
|
_rhoRight = rhoVol;
|
|
_pRight = pVol;
|
|
_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);
|
|
double u = _rhou[i] / rho;
|
|
double p = Pressure(i);
|
|
double h = _gamma / (_gamma - 1.0) * p / rho;
|
|
return h + 0.5 * u * u;
|
|
}
|
|
|
|
private double Pressure(int i) =>
|
|
(_gamma - 1.0) * (_E[i] - 0.5 * _rhou[i] * _rhou[i] / Math.Max(_rho[i], 1e-12));
|
|
|
|
private void HLLCFlux(double rL, double uL, double pL,
|
|
double rR, double uR, double pR,
|
|
out double fm, out double fp, out double fe)
|
|
{
|
|
double cL = Math.Sqrt(_gamma * pL / Math.Max(rL, 1e-12));
|
|
double cR = Math.Sqrt(_gamma * pR / Math.Max(rR, 1e-12));
|
|
double EL = pL / ((_gamma - 1) * rL) + 0.5 * uL * uL;
|
|
double ER = pR / ((_gamma - 1) * rR) + 0.5 * uR * uR;
|
|
double SL = Math.Min(uL - cL, uR - cR);
|
|
double SR = Math.Max(uL + cL, uR + cR);
|
|
|
|
double Ss = (pR - pL + rL * uL * (SL - uL) - rR * uR * (SR - uR))
|
|
/ (rL * (SL - uL) - rR * (SR - uR));
|
|
|
|
double FrL_m = rL * uL, FrL_p = rL * uL * uL + pL, FrL_e = (rL * EL + pL) * uL;
|
|
double FrR_m = rR * uR, FrR_p = rR * uR * uR + pR, FrR_e = (rR * ER + pR) * uR;
|
|
|
|
if (SL >= 0) { fm = FrL_m; fp = FrL_p; fe = FrL_e; }
|
|
else if (SR <= 0) { fm = FrR_m; fp = FrR_p; fe = FrR_e; }
|
|
else if (Ss >= 0)
|
|
{
|
|
double rsL = rL * (SL - uL) / (SL - Ss);
|
|
double ps = pL + rL * (SL - uL) * (Ss - uL);
|
|
double EsL = EL + (Ss - uL) * (Ss + pL / (rL * (SL - uL)));
|
|
fm = rsL * Ss; fp = rsL * Ss * Ss + ps; fe = (rsL * EsL + ps) * Ss;
|
|
}
|
|
else
|
|
{
|
|
double rsR = rR * (SR - uR) / (SR - Ss);
|
|
double ps = pL + rL * (SL - uL) * (Ss - uL);
|
|
double EsR = ER + (Ss - uR) * (Ss + pR / (rR * (SR - uR)));
|
|
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);
|
|
}
|
|
}
|
|
} |