427 lines
17 KiB
C#
427 lines
17 KiB
C#
using System;
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using System.Diagnostics;
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using FluidSim.Interfaces;
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namespace FluidSim.Components
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{
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/// <summary>
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/// 1‑D compressible Euler pipe with Lax‑Friedrichs finite‑volume scheme.
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/// Ghost states are set externally via SetGhostLeft/Right; they are always required.
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/// </summary>
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public class Pipe1D : IComponent
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{
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// ---------- Compile‑time profiling flag ----------
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public const bool EnableDetailedProfiling = false; // set to false in release builds
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public Port PortA { get; }
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public Port PortB { get; }
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public double Area { get; }
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public double DampingMultiplier { get; set; } = 1.0;
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public double EnergyRelaxationRate { get; set; } = 0.0; // 1/s
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private double _ambientPressure = 101325.0;
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public double AmbientPressure
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{
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get => _ambientPressure;
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set
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{
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_ambientPressure = value;
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_ambientEnergyReference = value / (_gamma - 1.0);
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}
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}
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private readonly int _n;
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private readonly double _dx;
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private readonly double _diameter;
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private readonly double _gamma = 1.4;
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private double[] _rho, _rhou, _E;
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private double[] _fluxM, _fluxP, _fluxE; // flux at cell faces (0.._n) – kept for possible external use, not used internally anymore
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private double _rhoGhostL, _uGhostL, _pGhostL;
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private double _rhoGhostR, _uGhostR, _pGhostR;
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private bool _ghostLValid, _ghostRValid;
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private double _laminarCoeff;
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private double _ambientEnergyReference;
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// ---------- Profiling accumulators ----------
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private long _profPrecomputeTicks;
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private long _profLeftFluxTicks;
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private long _profInteriorLoopTicks;
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private long _profRightFluxTicks;
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private long _profPortUpdateTicks;
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private long _profCallCount;
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public Pipe1D(double length, double area, int cellCount)
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{
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if (cellCount < 4) throw new ArgumentException("cellCount must be at least 4");
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_n = cellCount;
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_dx = length / _n;
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Area = area;
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_diameter = 2.0 * Math.Sqrt(area / Math.PI);
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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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_fluxM = new double[_n + 1];
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_fluxP = new double[_n + 1];
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_fluxE = new double[_n + 1];
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double mu_air = 1.8e-5;
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double radius = _diameter * 0.5;
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_laminarCoeff = 8.0 * mu_air / (radius * radius);
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_ambientEnergyReference = 101325.0 / (_gamma - 1.0);
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PortA = new Port { Owner = this };
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PortB = new Port { Owner = this };
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SetUniformState(1.225, 0.0, 101325.0);
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}
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IReadOnlyList<Port> IComponent.Ports => new[] { PortA, PortB };
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public void UpdateState(double dt) { }
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// ---------- Ghost interface ----------
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public void SetGhostLeft(double rho, double u, double p)
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{
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_rhoGhostL = rho; _uGhostL = u; _pGhostL = p; _ghostLValid = true;
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}
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public void SetGhostRight(double rho, double u, double p)
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{
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_rhoGhostR = rho; _uGhostR = u; _pGhostR = p; _ghostRValid = true;
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}
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public void ClearGhostFlags() { _ghostLValid = false; _ghostRValid = false; }
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public (double rho, double u, double p) GetInteriorStateLeft()
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{
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double rho = Math.Max(_rho[0], 1e-12);
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double u = _rhou[0] / rho;
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double p = PressureScalar(0);
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return (rho, u, p);
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}
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public (double rho, double u, double p) GetInteriorStateRight()
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{
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double rho = Math.Max(_rho[_n - 1], 1e-12);
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double u = _rhou[_n - 1] / rho;
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double p = PressureScalar(_n - 1);
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return (rho, u, p);
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}
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public int CellCount => _n;
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public double GetCellDensity(int i) => _rho[i];
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public double GetCellVelocity(int i) => _rhou[i] / Math.Max(_rho[i], 1e-12);
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public double GetCellPressure(int i) => PressureScalar(i);
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public int GetRequiredSubSteps(double dtGlobal, double cflTarget = 0.8)
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{
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double maxW = 0.0;
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for (int i = 0; i < _n; i++)
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{
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double rho = Math.Max(_rho[i], 1e-12);
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double u = Math.Abs(_rhou[i] / rho);
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double p = PressureScalar(i);
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double c = Math.Sqrt(_gamma * p / rho);
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double local = u + c;
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if (local > maxW) maxW = local;
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}
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maxW = Math.Max(maxW, 1e-8);
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return Math.Max(1, (int)Math.Ceiling(dtGlobal * maxW / (cflTarget * _dx)));
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}
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// ---------- Main step (per sub‑step) ----------
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public void SimulateSingleStep(double dtSub)
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{
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if (!_ghostLValid || !_ghostRValid)
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throw new InvalidOperationException("Ghost cells not set before SimulateSingleStep.");
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double dt = dtSub;
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int n = _n;
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double dt_dx = dt / _dx;
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double coeff = _laminarCoeff * DampingMultiplier;
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double relaxRate = EnergyRelaxationRate;
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double gamma = _gamma;
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double gm1 = gamma - 1.0;
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// ---------- Profiling start ----------
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long t0 = 0, t1 = 0;
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if (EnableDetailedProfiling)
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{
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t0 = Stopwatch.GetTimestamp();
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_profCallCount++;
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}
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// ---------- Phase 1: Pre‑compute pressure and speed of sound ----------
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double[] p = new double[n];
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double[] c = new double[n];
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for (int i = 0; i < n; i++)
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{
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double rho = Math.Max(_rho[i], 1e-12);
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double u = _rhou[i] / rho;
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p[i] = gm1 * (_E[i] - 0.5 * _rhou[i] * _rhou[i] / rho);
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c[i] = Math.Sqrt(gamma * p[i] / rho);
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}
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if (EnableDetailedProfiling)
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{
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t1 = Stopwatch.GetTimestamp();
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_profPrecomputeTicks += (t1 - t0);
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t0 = t1;
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}
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// ---------- Phase 2: Left face flux (ghostL – cell 0) ----------
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double rL_ghost = Math.Max(_rhoGhostL, 1e-12);
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double pL_ghost = _pGhostL;
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double uL_ghost = _uGhostL;
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double cL_ghost = Math.Sqrt(gamma * pL_ghost / rL_ghost);
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LaxFlux(rL_ghost, uL_ghost, pL_ghost, cL_ghost,
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_rho[0], _rhou[0] / Math.Max(_rho[0], 1e-12), p[0], c[0],
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out double fluxM_left, out double fluxP_left, out double fluxE_left);
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if (EnableDetailedProfiling)
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{
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t1 = Stopwatch.GetTimestamp();
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_profLeftFluxTicks += (t1 - t0);
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t0 = t1;
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}
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// ---------- Phase 3: Interior loop (fluxes + cell updates) ----------
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double fluxM_prev = fluxM_left;
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double fluxP_prev = fluxP_left;
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double fluxE_prev = fluxE_left;
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for (int i = 0; i < n - 1; i++)
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{
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int iL = i;
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int iR = i + 1;
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double rL = Math.Max(_rho[iL], 1e-12);
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double uL = _rhou[iL] / rL;
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double pL = p[iL];
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double cL = c[iL];
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double rR = Math.Max(_rho[iR], 1e-12);
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double uR = _rhou[iR] / rR;
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double pR = p[iR];
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double cR = c[iR];
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LaxFlux(rL, uL, pL, cL, rR, uR, pR, cR,
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out double fluxM_right, out double fluxP_right, out double fluxE_right);
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// Update cell i
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double r = _rho[i];
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double ru = _rhou[i];
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double E = _E[i];
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double newR = r - dt_dx * (fluxM_right - fluxM_prev);
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double newRu = ru - dt_dx * (fluxP_right - fluxP_prev);
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double newE = E - dt_dx * (fluxE_right - fluxE_prev);
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double dampingFactor = Math.Exp(-coeff / Math.Max(r, 1e-12) * dt);
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newRu *= dampingFactor;
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double relaxFactor = Math.Exp(-relaxRate * dt);
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newE = _ambientEnergyReference + (newE - _ambientEnergyReference) * relaxFactor;
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newR = Math.Max(newR, 1e-12);
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double kin = 0.5 * newRu * newRu / Math.Max(newR, 1e-12);
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double eMin = 100.0 / gm1 + kin;
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newE = Math.Max(newE, eMin);
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_rho[i] = newR;
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_rhou[i] = newRu;
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_E[i] = newE;
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fluxM_prev = fluxM_right;
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fluxP_prev = fluxP_right;
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fluxE_prev = fluxE_right;
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}
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if (EnableDetailedProfiling)
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{
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t1 = Stopwatch.GetTimestamp();
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_profInteriorLoopTicks += (t1 - t0);
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t0 = t1;
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}
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// ---------- Phase 4: Right face flux (cell n‑1 – ghostR) ----------
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double rR_ghost = Math.Max(_rhoGhostR, 1e-12);
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double pR_ghost = _pGhostR;
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double uR_ghost = _uGhostR;
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double cR_ghost = Math.Sqrt(gamma * pR_ghost / rR_ghost);
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LaxFlux(_rho[n - 1], _rhou[n - 1] / Math.Max(_rho[n - 1], 1e-12), p[n - 1], c[n - 1],
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rR_ghost, uR_ghost, pR_ghost, cR_ghost,
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out double fluxM_right_final, out double fluxP_right_final, out double fluxE_right_final);
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// Update last cell (identical to interior, but with final fluxes)
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{
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int i = n - 1;
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double r = _rho[i];
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double ru = _rhou[i];
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double E = _E[i];
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double newR = r - dt_dx * (fluxM_right_final - fluxM_prev);
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double newRu = ru - dt_dx * (fluxP_right_final - fluxP_prev);
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double newE = E - dt_dx * (fluxE_right_final - fluxE_prev);
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double dampingFactor = Math.Exp(-coeff / Math.Max(r, 1e-12) * dt);
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newRu *= dampingFactor;
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double relaxFactor = Math.Exp(-relaxRate * dt);
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newE = _ambientEnergyReference + (newE - _ambientEnergyReference) * relaxFactor;
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newR = Math.Max(newR, 1e-12);
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double kin = 0.5 * newRu * newRu / Math.Max(newR, 1e-12);
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double eMin = 100.0 / gm1 + kin;
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newE = Math.Max(newE, eMin);
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_rho[i] = newR;
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_rhou[i] = newRu;
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_E[i] = newE;
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}
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if (EnableDetailedProfiling)
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{
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t1 = Stopwatch.GetTimestamp();
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_profRightFluxTicks += (t1 - t0);
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t0 = t1;
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}
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// ---------- Phase 5: Update port states ----------
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(double rhoA, double uA, double pA) = GetInteriorStateLeft();
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PortA.Pressure = pA; PortA.Density = rhoA;
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PortA.Temperature = pA / (rhoA * 287.0);
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PortA.SpecificEnthalpy = gm1 / (gamma - 1.0) * pA / rhoA;
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(double rhoB, double uB, double pB) = GetInteriorStateRight();
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PortB.Pressure = pB; PortB.Density = rhoB;
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PortB.Temperature = pB / (rhoB * 287.0);
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PortB.SpecificEnthalpy = gm1 / (gamma - 1.0) * pB / rhoB;
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if (EnableDetailedProfiling)
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{
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t1 = Stopwatch.GetTimestamp();
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_profPortUpdateTicks += (t1 - t0);
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}
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}
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// ---------- Local Lax‑Friedrichs flux function ----------
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private void LaxFlux(double rL, double uL, double pL, double cL,
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double rR, double uR, double pR, double cR,
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out double fm, out double fp, out double fe)
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{
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double gm1 = _gamma - 1.0;
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double EL = pL / (gm1 * rL) + 0.5 * uL * uL;
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double ER = pR / (gm1 * rR) + 0.5 * uR * uR;
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double Fm_L = rL * uL;
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double Fp_L = rL * uL * uL + pL;
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double Fe_L = (rL * EL + pL) * uL;
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double Fm_R = rR * uR;
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double Fp_R = rR * uR * uR + pR;
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double Fe_R = (rR * ER + pR) * uR;
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double alpha = Math.Max(Math.Abs(uL) + cL, Math.Abs(uR) + cR);
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fm = 0.5 * (Fm_L + Fm_R) - 0.5 * alpha * (rR - rL);
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fp = 0.5 * (Fp_L + Fp_R) - 0.5 * alpha * (rR * uR - rL * uL);
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fe = 0.5 * (Fe_L + Fe_R) - 0.5 * alpha * (rR * ER - rL * EL);
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}
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// Original LaxFriedrichsFlux (kept for compatibility, can be removed if unused)
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private void LaxFriedrichsFlux(double rL, double uL, double pL, double eL,
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double rR, double uR, double pR, double eR,
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out double fm, out double fp, out double fe)
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{
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double rhoL = rL, rhoR = rR;
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double EL = rhoL * eL;
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double ER = rhoR * eR;
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double Fm_L = rhoL * uL;
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double Fp_L = rhoL * uL * uL + pL;
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double Fe_L = (EL + pL) * uL;
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double Fm_R = rhoR * uR;
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double Fp_R = rhoR * uR * uR + pR;
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double Fe_R = (ER + pR) * uR;
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double cL = Math.Sqrt(_gamma * pL / rL);
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double cR = Math.Sqrt(_gamma * pR / rR);
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double alpha = Math.Max(Math.Abs(uL) + cL, Math.Abs(uR) + cR);
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fm = 0.5 * (Fm_L + Fm_R) - 0.5 * alpha * (rhoR - rhoL);
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fp = 0.5 * (Fp_L + Fp_R) - 0.5 * alpha * (rhoR * uR - rhoL * uL);
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fe = 0.5 * (Fe_L + Fe_R) - 0.5 * alpha * (ER - EL);
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}
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private double PressureScalar(int i)
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{
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double rho = Math.Max(_rho[i], 1e-12);
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return (_gamma - 1.0) * (_E[i] - 0.5 * _rhou[i] * _rhou[i] / rho);
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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 - 1.0) * rho);
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double E = 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] = E;
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}
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}
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public void SetCellState(int i, double rho, double u, double p)
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{
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if (i < 0 || i >= _n) return;
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double e = p / ((_gamma - 1.0) * rho);
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double E = rho * e + 0.5 * rho * u * u;
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_rho[i] = rho;
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_rhou[i] = rho * u;
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_E[i] = E;
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}
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public void SetCellPressure(int i, double p)
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{
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if (i < 0 || i >= _n) return;
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double rho = _rho[i];
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double u = _rhou[i] / rho;
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double e = p / ((_gamma - 1.0) * rho);
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_E[i] = rho * e + 0.5 * rho * u * u;
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}
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// ---------- Public profiling interface ----------
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public void ResetDetailCounters()
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{
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_profPrecomputeTicks = 0;
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_profLeftFluxTicks = 0;
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_profInteriorLoopTicks = 0;
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_profRightFluxTicks = 0;
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_profPortUpdateTicks = 0;
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_profCallCount = 0;
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}
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public string GetDetailProfileReport()
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{
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if (!EnableDetailedProfiling)
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return "Detailed profiling disabled.";
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double freq = Stopwatch.Frequency;
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long totalTicks = _profPrecomputeTicks + _profLeftFluxTicks +
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_profInteriorLoopTicks + _profRightFluxTicks +
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_profPortUpdateTicks;
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if (totalTicks == 0) return "No profiling data.";
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double totalSec = totalTicks / freq;
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double avgCallSec = totalSec / _profCallCount;
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double avgCallUs = avgCallSec * 1e6;
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string report = $" Pipe detailed (over {_profCallCount} calls, total {totalSec * 1000:F2} ms):\n";
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report += $" Avg per call: {avgCallUs:F2} µs\n";
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report += $" Precompute p,c: {_profPrecomputeTicks * 100.0 / totalTicks:F1} % ({_profPrecomputeTicks / freq * 1e6 / _profCallCount:F2} µs/call)\n";
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report += $" Left face flux: {_profLeftFluxTicks * 100.0 / totalTicks:F1} % ({_profLeftFluxTicks / freq * 1e6 / _profCallCount:F2} µs/call)\n";
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report += $" Interior loop: {_profInteriorLoopTicks * 100.0 / totalTicks:F1} % ({_profInteriorLoopTicks / freq * 1e6 / _profCallCount:F2} µs/call)\n";
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report += $" Right face flux: {_profRightFluxTicks * 100.0 / totalTicks:F1} % ({_profRightFluxTicks / freq * 1e6 / _profCallCount:F2} µs/call)\n";
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report += $" Port update: {_profPortUpdateTicks * 100.0 / totalTicks:F1} % ({_profPortUpdateTicks / freq * 1e6 / _profCallCount:F2} µs/call)\n";
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return report;
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}
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}
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} |