Add project files.
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17
Components/Connection.cs
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17
Components/Connection.cs
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using FluidSim.Interfaces;
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namespace FluidSim.Components
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{
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/// <summary>Pure data link between two ports, with orifice parameters.</summary>
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public class Connection
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{
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public Port PortA { get; }
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public Port PortB { get; }
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public double Area { get; set; } = 1e-5; // effective orifice area (m²)
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public double DischargeCoefficient { get; set; } = 0.62;
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public double Gamma { get; set; } = 1.4;
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public Connection(Port a, Port b) => (PortA, PortB) = (a, b);
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}
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}
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73
Components/Orifice.cs
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73
Components/Orifice.cs
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using System;
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using FluidSim.Interfaces;
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namespace FluidSim.Components
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{
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public class Orifice
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{
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public Port PortA { get; }
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public Port PortB { get; }
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public double Area { get; set; }
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public double DischargeCoeff { get; set; } = 0.62;
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public double Gamma { get; set; } = 1.4;
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public Orifice(double area)
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{
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Area = area;
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PortA = new Port();
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PortB = new Port();
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}
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public void Simulate()
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{
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double pA = PortA.Pressure, pB = PortB.Pressure;
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double dp = pA - pB;
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double rho = dp >= 0 ? PortA.Density : PortB.Density;
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if (rho <= 0) rho = 1.225;
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double massFlow;
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double absDp = Math.Abs(dp);
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double critical = 1e-3 * pA; // blend threshold
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if (absDp < critical)
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{
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// Linearised region for numerical stability
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massFlow = Area * DischargeCoeff * Math.Sqrt(2 * rho * critical) * dp / critical;
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}
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else
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{
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double sign = Math.Sign(dp);
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double pratio = Math.Min(pA, pB) / Math.Max(pA, pB);
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double choked = Math.Pow(2.0 / (Gamma + 1.0), Gamma / (Gamma - 1.0));
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if (pratio < choked)
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{
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double term = Math.Sqrt(Gamma * Math.Pow(2.0 / (Gamma + 1.0), (Gamma + 1.0) / (Gamma - 1.0)));
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massFlow = DischargeCoeff * Area * Math.Sqrt(rho * Math.Max(pA, pB)) * term;
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}
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else
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{
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double exp = 1.0 - Math.Pow(pratio, (Gamma - 1.0) / Gamma);
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massFlow = DischargeCoeff * Area *
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Math.Sqrt(2.0 * rho * Math.Max(pA, pB) * (Gamma / (Gamma - 1.0)) * pratio * pratio * exp);
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}
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massFlow *= sign;
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}
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PortA.MassFlowRate = -massFlow; // outflow from A
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PortB.MassFlowRate = massFlow; // inflow to B
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if (massFlow > 0) // A->B
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{
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PortA.SpecificEnthalpy = PortA.SpecificEnthalpy;
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PortB.SpecificEnthalpy = PortA.SpecificEnthalpy;
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}
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else
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{
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PortA.SpecificEnthalpy = PortB.SpecificEnthalpy;
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PortB.SpecificEnthalpy = PortB.SpecificEnthalpy;
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}
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}
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}
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}
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170
Components/Pipe1D.cs
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170
Components/Pipe1D.cs
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using System;
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using FluidSim.Interfaces;
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namespace FluidSim.Components
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{
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public class Pipe1D
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{
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public Port PortA { get; }
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public Port PortB { get; }
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public double Area => _area;
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private int _n;
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private double _dx, _dt, _gamma = 1.4, _area;
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private double[] _rho, _rhou, _E;
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// Boundary fluxes (set by solver before each step)
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private double _fxL_mass, _fxL_mom, _fxL_ener;
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private double _fxR_mass, _fxR_mom, _fxR_ener;
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private bool _leftSet, _rightSet;
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public double FrictionFactor { get; set; } = 0.02;
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public int GetCellCount() => _n;
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public double GetCellDensity(int i) => _rho[i];
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public double GetCellPressure(int i) => Pressure(i);
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public double GetCellVelocity(int i) => _rhou[i] / Math.Max(_rho[i], 1e-12);
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public Pipe1D(double length, double area, int nCells, int sampleRate)
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{
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_n = nCells;
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_dx = length / nCells;
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_dt = 1.0 / sampleRate;
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_area = area;
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_rho = new double[_n];
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_rhou = new double[_n];
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_E = new double[_n];
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PortA = new Port();
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PortB = new Port();
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}
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public void SetUniformState(double rho, double u, double p)
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{
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double e = p / ((_gamma - 1) * rho);
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double Etot = rho * e + 0.5 * rho * u * u;
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for (int i = 0; i < _n; i++)
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{
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_rho[i] = rho;
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_rhou[i] = rho * u;
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_E[i] = Etot;
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}
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}
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public double GetLeftPressure() => Pressure(0);
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public double GetRightPressure() => Pressure(_n - 1);
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public double GetLeftDensity() => _rho[0];
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public double GetRightDensity() => _rho[_n - 1];
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public void SetLeftBoundaryFlux(double m, double p, double e)
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{
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_fxL_mass = m; _fxL_mom = p; _fxL_ener = e; _leftSet = true;
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}
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public void SetRightBoundaryFlux(double m, double p, double e)
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{
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_fxR_mass = m; _fxR_mom = p; _fxR_ener = e; _rightSet = true;
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}
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public void Simulate()
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{
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int n = _n;
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double[] Fm = new double[n + 1], Fp = new double[n + 1], Fe = new double[n + 1];
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// Left face
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if (_leftSet) { Fm[0] = _fxL_mass; Fp[0] = _fxL_mom; Fe[0] = _fxL_ener; }
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else { Fm[0] = 0; Fp[0] = Pressure(0); Fe[0] = 0; } // reflective wall
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// Internal faces (HLLC)
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for (int i = 0; i < n - 1; i++)
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{
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double uL = _rhou[i] / Math.Max(_rho[i], 1e-12);
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double uR = _rhou[i + 1] / Math.Max(_rho[i + 1], 1e-12);
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HLLCFlux(_rho[i], uL, Pressure(i), _rho[i + 1], uR, Pressure(i + 1),
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out Fm[i + 1], out Fp[i + 1], out Fe[i + 1]);
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}
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// Right face
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if (_rightSet) { Fm[n] = _fxR_mass; Fp[n] = _fxR_mom; Fe[n] = _fxR_ener; }
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else { Fm[n] = 0; Fp[n] = Pressure(n - 1); Fe[n] = 0; }
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// Update cells
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for (int i = 0; i < n; i++)
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{
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double dM = (Fm[i + 1] - Fm[i]) / _dx;
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double dP = (Fp[i + 1] - Fp[i]) / _dx;
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double dE = (Fe[i + 1] - Fe[i]) / _dx;
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_rho[i] -= _dt * dM;
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_rhou[i] -= _dt * dP;
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_E[i] -= _dt * dE;
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// Clamp to physical
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if (_rho[i] < 1e-12) _rho[i] = 1e-12;
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double u = _rhou[i] / _rho[i];
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double kinetic = 0.5 * _rho[i] * u * u;
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if (_E[i] < kinetic) _E[i] = kinetic;
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}
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// Friction
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if (FrictionFactor > 0)
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{
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double D = 2.0 * Math.Sqrt(_area / Math.PI);
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for (int i = 0; i < n; i++)
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{
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double u = _rhou[i] / Math.Max(_rho[i], 1e-12);
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double f = FrictionFactor / (2.0 * D) * _rho[i] * u * Math.Abs(u);
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_rhou[i] -= _dt * f;
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if (_E[i] > _dt * f * u) _E[i] -= _dt * f * u;
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}
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}
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// Write port flows for the solver
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PortA.MassFlowRate = _leftSet ? _fxL_mass * _area : 0.0;
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PortB.MassFlowRate = _rightSet ? -_fxR_mass * _area : 0.0;
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// Enthalpy for upwinding
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PortA.SpecificEnthalpy = _gamma / (_gamma - 1.0) * Pressure(0) / Math.Max(_rho[0], 1e-12);
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PortB.SpecificEnthalpy = _gamma / (_gamma - 1.0) * Pressure(_n - 1) / Math.Max(_rho[_n - 1], 1e-12);
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// Reset for next step
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_leftSet = _rightSet = false;
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}
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double Pressure(int i) =>
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(_gamma - 1.0) * (_E[i] - 0.5 * _rhou[i] * _rhou[i] / Math.Max(_rho[i], 1e-12));
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void HLLCFlux(double rL, double uL, double pL, double rR, double uR, double pR,
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out double fm, out double fp, out double fe)
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{
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double cL = Math.Sqrt(_gamma * pL / Math.Max(rL, 1e-12));
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double cR = Math.Sqrt(_gamma * pR / Math.Max(rR, 1e-12));
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double EL = pL / ((_gamma - 1) * rL) + 0.5 * uL * uL;
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double ER = pR / ((_gamma - 1) * rR) + 0.5 * uR * uR;
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double SL = Math.Min(uL - cL, uR - cR);
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double SR = Math.Max(uL + cL, uR + cR);
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double Ss = (pR - pL + rL * uL * (SL - uL) - rR * uR * (SR - uR))
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/ (rL * (SL - uL) - rR * (SR - uR));
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double FrL_m = rL * uL, FrL_p = rL * uL * uL + pL, FrL_e = (rL * EL + pL) * uL;
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double FrR_m = rR * uR, FrR_p = rR * uR * uR + pR, FrR_e = (rR * ER + pR) * uR;
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if (SL >= 0) { fm = FrL_m; fp = FrL_p; fe = FrL_e; }
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else if (SR <= 0) { fm = FrR_m; fp = FrR_p; fe = FrR_e; }
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else if (Ss >= 0)
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{
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double rsL = rL * (SL - uL) / (SL - Ss);
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double ps = pL + rL * (SL - uL) * (Ss - uL);
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double EsL = EL + (Ss - uL) * (Ss + pL / (rL * (SL - uL)));
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fm = rsL * Ss; fp = rsL * Ss * Ss + ps; fe = (rsL * EsL + ps) * Ss;
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}
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else
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{
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double rsR = rR * (SR - uR) / (SR - Ss);
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double ps = pL + rL * (SL - uL) * (Ss - uL);
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double EsR = ER + (Ss - uR) * (Ss + pR / (rR * (SR - uR)));
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fm = rsR * Ss; fp = rsR * Ss * Ss + ps; fe = (rsR * EsR + ps) * Ss;
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}
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}
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}
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}
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71
Components/Volume0D.cs
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71
Components/Volume0D.cs
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using System;
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using FluidSim.Interfaces;
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using FluidSim.Utils;
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namespace FluidSim.Components
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{
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public class Volume0D
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{
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public Port Port { get; private set; }
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public double Mass { get; private set; }
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public double InternalEnergy { get; private set; }
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public double Gamma { get; set; } = 1.4;
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public double GasConstant { get; set; } = 287.0;
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public double Volume { get; set; }
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public double dVdt { get; set; }
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private double _dt;
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public double Density => Mass / Volume;
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public double Pressure => (Gamma - 1.0) * InternalEnergy / Volume;
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public double Temperature => Pressure / (Density * GasConstant);
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public double SpecificEnthalpy => Gamma / (Gamma - 1.0) * Pressure / Density;
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public Volume0D(double initialVolume, double initialPressure,
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double initialTemperature, int sampleRate,
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double gasConstant = 287.0, double gamma = 1.4)
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{
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GasConstant = gasConstant;
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Gamma = gamma;
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Volume = initialVolume;
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dVdt = 0.0;
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_dt = 1.0 / sampleRate;
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double rho0 = initialPressure / (GasConstant * initialTemperature);
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Mass = rho0 * Volume;
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InternalEnergy = (initialPressure * Volume) / (Gamma - 1.0);
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Port = new Port();
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PushStateToPort();
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}
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public void PushStateToPort()
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{
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Port.Pressure = Pressure;
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Port.Density = Density;
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Port.Temperature = Temperature;
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Port.SpecificEnthalpy = SpecificEnthalpy;
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}
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public void Integrate()
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{
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double mdot = Port.MassFlowRate;
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double h_in = Port.SpecificEnthalpy;
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double dm = mdot * _dt;
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double dE = (mdot * h_in) * _dt - Pressure * dVdt * _dt;
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Mass += dm;
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InternalEnergy += dE;
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// Hard physical bounds – prevent NaN and unphysical states
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if (Mass < 1e-12) Mass = 1e-12;
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if (InternalEnergy < 1e-12) InternalEnergy = 1e-12;
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PushStateToPort();
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}
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}
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}
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