Add a dummy flow variable for balance

dietmarw · dietmarw · commit 1ef4615d7996 · 2026-04-10T16:55:43.000+02:00
diff --git a/OpenHPL/Interfaces/Contact.mo b/OpenHPL/Interfaces/Contact.mo
@@ -4,6 +4,7 @@ connector Contact "Water flow connector"
   //SI.Temperature T "Contact temperature";
   flow SI.MassFlowRate mdot "Mass flow rate through the contact";
   SI.Height z "Elevation at connection point";
+  flow Real gz(unit="m2/s") "Auxiliary elevation flow variable (always zero, for connector balance)";
   annotation (
     Documentation(info = "<html>
 <p>Contact is a basic water flow connector, which consists of water pressure, mass flow rate,
diff --git a/OpenHPL/Interfaces/TwoContacts.mo b/OpenHPL/Interfaces/TwoContacts.mo
@@ -6,6 +6,8 @@ partial model TwoContacts "Model of two connectors"
   Contact_o o "Outlet contact (positive design flow direction is from i to o)"
                                annotation (
     Placement(transformation(extent={{90,-10},{110,10}})));
+equation
+  i.gz = 0 "Elevation auxiliary variable (no elevation source/sink at this connection point)";
   annotation (
     Documentation(info = "<html>
     <p>TwoContact is a partial model, which consists of two Contacts <em>i</em>and <em>o</em>.
diff --git a/OpenHPL/Waterway/Reservoir.mo b/OpenHPL/Waterway/Reservoir.mo
@@ -80,6 +80,7 @@ equation
 
    o.mdot = -data.rho * Vdot_o "Output flow connector";
   o.z = z_0 "Set absolute elevation at outlet";
+  o.gz = 0 "Elevation auxiliary variable";
   //o.T = T_0 "TBD: Output temperature connector";
   annotation (preferredView="info", Documentation(info="<html>
 <h4>Reservoir Model</h4>
diff --git a/OpenHPL/Waterway/ReservoirChannel.mo b/OpenHPL/Waterway/ReservoirChannel.mo
@@ -33,6 +33,7 @@ equation
   o.mdot =-q*W*data.rho;
   o.p = data.p_a + data.rho * data.g * openChannel.h[N];
   o.z = z_0 "Set absolute elevation at outlet";
+  o.gz = 0 "Elevation auxiliary variable";
   annotation (
     Documentation(preferredView="info", info="<html>
 <h4>Reservoir Channel Model</h4>
diff --git a/OpenHPL/Waterway/SurgeTank.mo b/OpenHPL/Waterway/SurgeTank.mo
@@ -59,7 +59,8 @@ model SurgeTank "Model of the surge tank/shaft"
 
   Interfaces.Contact_i creek(
     p = p_t + data.rho * data.g * (h - H_creek),
-    mdot = mdot_creek) if useCreekIntake "Creek intake connector (connects to VolumeFlowSource)"
+    mdot = mdot_creek,
+    gz = 0) if useCreekIntake "Creek intake connector (connects to VolumeFlowSource)"
     annotation (Placement(transformation(extent = {{-10, 90}, {10, 110}})));
 
 protected
diff --git a/OpenHPL/Waterway/VolumeFlowSource.mo b/OpenHPL/Waterway/VolumeFlowSource.mo
@@ -39,6 +39,7 @@ equation
       pattern=LinePattern.Dot));
   o.mdot = -data.rho*Vdot;
   o.z = z_0 "Set absolute elevation at outlet";
+  o.gz = 0 "Elevation auxiliary variable";
   connect(constantVolumeFlow.y, Vdot) annotation (Line(points={{-39,40},{40,40},{40,0},{80,0}}, color={0,0,127}));
   connect(firstOrder.u, outFlow) annotation (Line(
       points={{-62,-20},{-80,-20},{-80,0},{-120,0}},
