orifice confirmed working

Components/Volume0D.cs

@@ -4,23 +4,17 @@ using FluidSim.Interfaces;
 
 namespace FluidSim.Components
 {
-    /// <summary>
-    /// Zero‑dimensional control volume with arbitrary number of ports.
-    /// Integrates mass and energy fluxes from all ports.
-    /// Safeguards keep a tiny amount of gas to avoid negative states.
-    /// </summary>
     public class Volume0D : IComponent
     {
         public List<Port> Ports { get; } = new List<Port>();
 
-        public double Mass { get; private set; }
-        public double InternalEnergy { get; private set; }
+        public double Mass { get; set; }           // made public setter
+        public double InternalEnergy { get; set; }  // made public setter
         public double Volume { get; set; }
         public double Dvdt { get; set; }
         public double Gamma { get; set; } = 1.4;
         public double GasConstant { get; set; } = 287.0;
 
-        // Ambient pressure used for emergency refill – default 101325 Pa
         public double AmbientPressure { get; set; } = 101325.0;
 
         // Derived quantities
@@ -42,11 +36,9 @@ namespace FluidSim.Components
             InternalEnergy = (initialPressure * Volume) / (Gamma - 1.0);
         }
 
-        /// <summary>Add a new port and initialise it to the volume's current state.</summary>
         public Port CreatePort()
         {
             var port = new Port { Owner = this };
-            // Set the port state immediately to avoid a mismatch before the first integration
             port.Pressure = Pressure;
             port.Density = Density;
             port.Temperature = Temperature;
@@ -56,9 +48,18 @@ namespace FluidSim.Components
         }
 
         /// <summary>
-        /// Integrate over dt using the MassFlowRate and SpecificEnthalpy
-        /// that have been set on each port during the coupling resolution phase.
+        /// Set the pressure to a specific value while keeping the current temperature constant.
+        /// Updates Mass and InternalEnergy accordingly.
         /// </summary>
+        public void SetPressure(double pressure)
+        {
+            double V = Math.Max(Volume, 1e-12);
+            double currentT = Temperature;   // current temperature before changes
+            double rho = pressure / (GasConstant * currentT);
+            Mass = rho * V;
+            InternalEnergy = pressure * V / (Gamma - 1.0);
+        }
+
         public void UpdateState(double dt)
         {
             double totalMdot = 0.0;
@@ -67,17 +68,15 @@ namespace FluidSim.Components
             foreach (var port in Ports)
             {
                 totalMdot += port.MassFlowRate;
-                // mdot * h gives energy flow: positive mdot = inflow, negative = outflow
                 totalEdot += port.MassFlowRate * port.SpecificEnthalpy;
             }
 
             double dm = totalMdot * dt;
-            double dE = totalEdot * dt - Pressure * Dvdt * dt;   // piston work
+            double dE = totalEdot * dt - Pressure * Dvdt * dt;
 
             Mass += dm;
             InternalEnergy += dE;
 
-            // Safeguards: keep at least 1 µg of gas at a small pressure
             double V = Math.Max(Volume, 1e-12);
             if (Mass < 1e-9)
             {
@@ -89,18 +88,16 @@ namespace FluidSim.Components
                 InternalEnergy = AmbientPressure * V / (Gamma - 1.0);
             }
 
-            // Final non‑negative clamps (should not be needed after above)
             if (Mass < 0.0) Mass = 1e-9;
             if (InternalEnergy < 0.0) InternalEnergy = AmbientPressure * V / (Gamma - 1.0);
 
-            // Push updated state back to all ports
             double p = Pressure, rho = Density, T = Temperature, h = SpecificEnthalpy;
             foreach (var port in Ports)
             {
                 port.Pressure = p;
                 port.Density = rho;
                 port.Temperature = T;
-                port.SpecificEnthalpy = h;   // will be overwritten by couplings for inflow, but this is the default
+                port.SpecificEnthalpy = h;
             }
         }