Add project files.

Interfaces/Junction0.cs

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+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace FluidSim.Interfaces
+{
+    internal class Junction0
+    {
+    }
+}

Interfaces/Junction1.cs

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+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace FluidSim.Interfaces
+{
+    internal class Junction1
+    {
+    }
+}

Interfaces/Port.cs

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+namespace FluidSim.Interfaces
+{
+    public class Port
+    {
+        public double Pressure;             // Pa
+        public double MassFlowRate;         // kg/s, positive INTO the component
+        public double SpecificEnthalpy;     // J/kg, enthalpy of fluid entering this port
+        public double Density;              // kg/m³
+        public double Temperature;          // K
+
+        public Port()
+        {
+            Pressure = 101325.0;
+            MassFlowRate = 0.0;
+            SpecificEnthalpy = 0.0;
+            Density = 1.225;
+            Temperature = 300.0;
+        }
+    }
+}