Known bad point (unphysical energy loss)

Components/Pipe1D.cs

@@ -67,6 +67,8 @@ namespace FluidSim.Components
             _fxR_mass = m; _fxR_mom = p; _fxR_ener = e; _rightSet = true;
         }
 
+
+
         public void Simulate()
         {
             int n = _n;
@@ -106,16 +108,15 @@ namespace FluidSim.Components
                 if (_E[i] < kinetic) _E[i] = kinetic;
             }
 
-            // Friction
+            // Friction (energy‑conserving)
             if (FrictionFactor > 0)
             {
                 double D = 2.0 * Math.Sqrt(_area / Math.PI);
-                for (int i = 0; i < n; i++)
+                for (int i = 0; i < _n; i++)
                 {
                     double u = _rhou[i] / Math.Max(_rho[i], 1e-12);
                     double f = FrictionFactor / (2.0 * D) * _rho[i] * u * Math.Abs(u);
-                    _rhou[i] -= _dt * f;
+                    //_rhou[i] -= _dt * f; FRICTIN DISABLED!!!
-                    if (_E[i] > _dt * f * u) _E[i] -= _dt * f * u;
                 }
             }
 
@@ -124,13 +125,22 @@ namespace FluidSim.Components
             PortB.MassFlowRate = _rightSet ? -_fxR_mass * _area : 0.0;
 
             // Enthalpy for upwinding
-            PortA.SpecificEnthalpy = _gamma / (_gamma - 1.0) * Pressure(0) / Math.Max(_rho[0], 1e-12);
+            PortA.SpecificEnthalpy = GetCellTotalSpecificEnthalpy(0);
-            PortB.SpecificEnthalpy = _gamma / (_gamma - 1.0) * Pressure(_n - 1) / Math.Max(_rho[_n - 1], 1e-12);
+            PortB.SpecificEnthalpy = GetCellTotalSpecificEnthalpy(_n - 1);
 
             // Reset for next step
             _leftSet = _rightSet = false;
         }
 
+        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;
+        }
+
         double Pressure(int i) =>
             (_gamma - 1.0) * (_E[i] - 0.5 * _rhou[i] * _rhou[i] / Math.Max(_rho[i], 1e-12));
 

Core/OrificeBoundary.cs

@@ -55,14 +55,19 @@ namespace FluidSim.Core
                                           bool isLeftBoundary,
                                           out double massFlux, out double momFlux, out double energyFlux)
         {
-            // mass flow from pipe to volume (positive = pipe → volume)
+            // ----- Compute STAGNATION pressures -----
-            double mdot = MassFlow(pPipe, rhoPipe, pVol, rhoVol, conn);
+            double pStagPipe = pPipe + 0.5 * rhoPipe * uPipe * uPipe;
+            double pStagVol = pVol + 0.5 * rhoVol * uVol * uVol;   // uVol is always 0 for your volumes
+
+            // Mass flow driven by stagnation pressure difference (positive = pipe→volume)
+            double mdot = MassFlow(pStagPipe, rhoPipe, pStagVol, rhoVol, conn);
 
             // Limit mass flow to the amount that can leave/enter the pipe cell
             double maxMdot = rhoPipe * pipeArea * 343.0;
             if (Math.Abs(mdot) > maxMdot) mdot = Math.Sign(mdot) * maxMdot;
 
-            bool flowLeavesPipe = mdot > 0;
+            bool flowLeavesPipe = mdot > 0;   // pipe → volume
+
             double uFace, pFace, rhoFace;
             double massFluxPerArea;
 
@@ -83,7 +88,7 @@ namespace FluidSim.Core
                 { uFace = uVol; pFace = pVol; rhoFace = rhoVol; }
             }
 
-            // Total enthalpy of the injected fluid (corrected: mass flux × total enthalpy)
+            // Total enthalpy of the injected fluid
             double specificEnthalpy = (1.4 / (1.4 - 1.0)) * pFace / Math.Max(rhoFace, 1e-12);
             double totalEnthalpy = specificEnthalpy + 0.5 * uFace * uFace;
 

Core/Simulation.cs

@@ -6,58 +6,46 @@ namespace FluidSim.Core
 {
     public static class Simulation
     {
+        private static Solver solver;
+        private static Volume0D volA, volB;
         private static Pipe1D pipe;
-        private static Connection leftConn, rightConn;   // dummy connections for orifice params
+        private static Connection connA, connB;
+        private static int stepCount;
         private static double time;
         private static double dt;
-        private static int stepCount;
 
         public static void Initialize(int sampleRate)
         {
             dt = 1.0 / sampleRate;
 
+            double V = 5.0 * Units.L;
+            volA = new Volume0D(V, 1.1 * Units.atm, Units.Celsius(20), sampleRate);
+            volB = new Volume0D(V, 1.0 * Units.atm, Units.Celsius(20), sampleRate);
+
             double length = 150 * Units.mm;
             double diameter = 25 * Units.mm;
             double area = Units.AreaFromDiameter(25, Units.mm);
             int nCells = 10;
 
             pipe = new Pipe1D(length, area, nCells, sampleRate);
-            pipe.SetUniformState(1.2, 0.0, 1.0 * Units.atm);   // start at 1 atm
+            pipe.SetUniformState(volA.Density, 0.0, volA.Pressure);
             pipe.FrictionFactor = 0.02;
 
-            // Dummy connections – only used for orifice parameters
+            // Connections with orifice area equal to pipe area (flange joint)
-            leftConn = new Connection(null, null) { Area = area, DischargeCoefficient = 1.0, Gamma = 1.4 };
+            connA = new Connection(volA.Port, pipe.PortA) { Area = area, DischargeCoefficient = 1.0, Gamma = 1.4 };
-            rightConn = new Connection(null, null) { Area = area, DischargeCoefficient = 1.0, Gamma = 1.4 };
+            connB = new Connection(pipe.PortB, volB.Port) { Area = area, DischargeCoefficient = 1.0, Gamma = 1.4 };
+
+            solver = new Solver();
+            solver.AddVolume(volA);
+            solver.AddVolume(volB);
+            solver.AddPipe(pipe);
+            solver.AddConnection(connA);
+            solver.AddConnection(connB);
         }
 
         public static float Process()
         {
-            // Fixed boundary reservoirs
+            solver.Step();
-            double pLeft = 1.1 * Units.atm;
-            double rhoLeft = 1.2;
-            double uLeft = 0.0;
-
-            double pRight = 1.0 * Units.atm;
-            double rhoRight = 1.2;
-            double uRight = 0.0;
-
-            // Compute boundary fluxes via orifice model
-            OrificeBoundary.PipeVolumeFlux(
-                pipe.GetLeftPressure(), pipe.GetLeftDensity(), 0.0,
-                pLeft, rhoLeft, uLeft,
-                leftConn, pipe.Area, true,
-                out double leftMassFlux, out double leftMomFlux, out double leftEnergyFlux);
-
-            OrificeBoundary.PipeVolumeFlux(
-                pipe.GetRightPressure(), pipe.GetRightDensity(), 0.0,
-                pRight, rhoRight, uRight,
-                rightConn, pipe.Area, false,
-                out double rightMassFlux, out double rightMomFlux, out double rightEnergyFlux);
-
-            pipe.SetLeftBoundaryFlux(leftMassFlux, leftMomFlux, leftEnergyFlux);
-            pipe.SetRightBoundaryFlux(rightMassFlux, rightMomFlux, rightEnergyFlux);
-            pipe.Simulate();
-
             time += dt;
             stepCount++;
             Log();
@@ -66,20 +54,13 @@ namespace FluidSim.Core
 
         public static void Log()
         {
-            if (stepCount <= 20 || stepCount % 50 == 0)
+            if (stepCount <= 50 || stepCount % 200 == 0)
             {
-                Console.WriteLine($"Step {stepCount:D4}  t = {time * 1e3:F3} ms");
+                Console.WriteLine(
-                for (int i = 0; i < pipe.GetCellCount(); i++)
+                    $"t = {time * 1e3:F3} ms  Step {stepCount:D4}: " +
-                {
+                    $"PA = {volA.Pressure / 1e5:F6} bar, " +
-                    double rho = pipe.GetCellDensity(i);
+                    $"PB = {volB.Pressure / 1e5:F6} bar, " +
-                    double p = pipe.GetCellPressure(i);
+                    $"FlowA = {pipe.PortA.MassFlowRate * 1e3:F2} g/s");
-                    double u = pipe.GetCellVelocity(i);
-                    Console.WriteLine($"  Cell {i}: ρ={rho:F4} kg/m³  p={p / 1e5:F6} bar  u={u:F3} m/s");
-                }
-                double leftFlow = pipe.PortA.MassFlowRate;
-                double rightFlow = pipe.PortB.MassFlowRate;
-                Console.WriteLine($"  Left flow = {leftFlow * 1e3:F4} g/s   Right flow = {rightFlow * 1e3:F4} g/s");
-                Console.WriteLine();
             }
         }
     }

Core/Solver.cs

@@ -20,7 +20,7 @@ namespace FluidSim.Core
             foreach (var v in _volumes)
                 v.PushStateToPort();
 
-            // 2. Apply orifice boundaries to pipes
+            // 2. Compute boundary fluxes (orifice model)
             foreach (var conn in _connections)
             {
                 if (IsPipePort(conn.PortA) && IsVolumePort(conn.PortB))
@@ -31,20 +31,20 @@ namespace FluidSim.Core
                     VolumeToVolume(conn);
             }
 
-            // 3. Pipes simulate
+            // 3. Pipe simulation step
             foreach (var p in _pipes)
                 p.Simulate();
 
-            // 4. Transfer pipe flows to connected volumes
+            // 4. Transfer pipe‑port data to volumes
             foreach (var conn in _connections)
             {
                 if (IsPipePort(conn.PortA) && IsVolumePort(conn.PortB))
-                    Transfer(conn.PortA, conn.PortB);
+                    TransferPipeToVolume(conn.PortA, conn.PortB);
                 else if (IsVolumePort(conn.PortA) && IsPipePort(conn.PortB))
-                    Transfer(conn.PortB, conn.PortA);
+                    TransferPipeToVolume(conn.PortB, conn.PortA);
             }
 
-            // 5. Volumes integrate
+            // 5. Integrate volumes
             foreach (var v in _volumes)
                 v.Integrate();
         }
@@ -61,34 +61,56 @@ namespace FluidSim.Core
 
             double pP = isLeft ? pipe.GetLeftPressure() : pipe.GetRightPressure();
             double rhoP = isLeft ? pipe.GetLeftDensity() : pipe.GetRightDensity();
-            double uP = 0.0;
+            double uP = isLeft ? pipe.GetCellVelocity(0)
-            double pV = volPort.Pressure, rhoV = volPort.Density, uV = 0.0;
+                               : pipe.GetCellVelocity(pipe.GetCellCount() - 1);
+
+            double pV = volPort.Pressure;
+            double rhoV = volPort.Density;
+            double uV = 0.0;   // volume has zero organized velocity
+
+            OrificeBoundary.PipeVolumeFlux(
+                pP, rhoP, uP,
+                pV, rhoV, uV,
+                conn, pipe.Area, isLeft,
+                out double massFlux, out double momFlux, out double energyFlux);
 
-            OrificeBoundary.PipeVolumeFlux(pP, rhoP, uP, pV, rhoV, uV, conn, pipe.Area,
-                isLeft, out double mf, out double pf, out double ef);
             if (isLeft)
-                pipe.SetLeftBoundaryFlux(mf, pf, ef);
+                pipe.SetLeftBoundaryFlux(massFlux, momFlux, energyFlux);
             else
-                pipe.SetRightBoundaryFlux(mf, pf, ef);
+                pipe.SetRightBoundaryFlux(massFlux, momFlux, energyFlux);
         }
 
         void VolumeToVolume(Connection conn)
         {
-            double mdot = OrificeBoundary.MassFlow(conn.PortA.Pressure, conn.PortA.Density,
+            double mdot = OrificeBoundary.MassFlow(
-                                                    conn.PortB.Pressure, conn.PortB.Density, conn);
+                conn.PortA.Pressure, conn.PortA.Density,
+                conn.PortB.Pressure, conn.PortB.Density, conn);
+
             conn.PortA.MassFlowRate = -mdot;
             conn.PortB.MassFlowRate = mdot;
+
             if (mdot > 0)
                 conn.PortB.SpecificEnthalpy = conn.PortA.SpecificEnthalpy;
             else if (mdot < 0)
                 conn.PortA.SpecificEnthalpy = conn.PortB.SpecificEnthalpy;
         }
 
-        void Transfer(Port pipePort, Port volPort)
+        void TransferPipeToVolume(Port pipePort, Port volPort)
         {
             double mdot = pipePort.MassFlowRate;
+            // mdot > 0 → fluid enters pipe from volume
+            // mdot < 0 → fluid leaves pipe and enters volume
+
+            // Volume mass flow sign is opposite (positive into volume)
             volPort.MassFlowRate = -mdot;
-            volPort.SpecificEnthalpy = pipePort.SpecificEnthalpy;
+
+            if (mdot < 0)  // pipe → volume
+            {
+                // ★ pipePort.SpecificEnthalpy now contains TOTAL enthalpy
+                volPort.SpecificEnthalpy = pipePort.SpecificEnthalpy;
+            }
+            // else: fluid goes volume → pipe → volume owns its own (static) enthalpy,
+            // which is already correct.
         }
     }
 }

Interfaces/Junction0.cs

@@ -1,10 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Text;
-
-namespace FluidSim.Interfaces
-{
-    internal class Junction0
-    {
-    }
-}

Interfaces/Junction1.cs

@@ -1,10 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Text;
-
-namespace FluidSim.Interfaces
-{
-    internal class Junction1
-    {
-    }
-}