Back-port of #3291 for the pump model into MSL 3.2.3 maintenance

modelica · Aug 7, 2020 · 1a4a823 · 1a4a823
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Showing 3 changed files with 24 additions and 4 deletions.
diff --git a/Modelica/Fluid/Examples/PumpingSystem.mo b/Modelica/Fluid/Examples/PumpingSystem.mo
@@ -28,6 +28,7 @@ model PumpingSystem "Model of a pumping system for drinking water"
 
   Machines.PrescribedPump pumps(
     checkValve=true,
+    checkValveHomotopy = Modelica.Fluid.Types.CheckValveHomotopyType.Closed,
     N_nominal=1200,
     redeclare function flowCharacteristic =
         Modelica.Fluid.Machines.BaseClasses.PumpCharacteristics.quadraticFlow (

diff --git a/Modelica/Fluid/Machines.mo b/Modelica/Fluid/Machines.mo
@@ -311,6 +311,8 @@ Then the model can be replaced with a Pump with rotational shaft or with a Presc
     parameter Medium.MassFlowRate m_flow_start = system.m_flow_start
         "Guess value of m_flow = port_a.m_flow"
       annotation(Dialog(tab = "Initialization"));
+    parameter Types.CheckValveHomotopyType checkValveHomotopy = Types.CheckValveHomotopyType.NoHomotopy "= whether the valve is Closed, Open, or unknown at initialization"
+      annotation(Dialog(tab = "Initialization"));
     final parameter SI.VolumeFlowRate V_flow_single_init = m_flow_start/rho_nominal/nParallel
         "Used for simplified initialization model";
     final parameter SI.Position delta_head_init = flowCharacteristic(V_flow_single_init*1.1)-flowCharacteristic(V_flow_single_init)
@@ -434,11 +436,21 @@ Then the model can be replaced with a Pump with rotational shaft or with a Presc
     else
       // Flow characteristics when check valve is open
       // The simplified model uses an approximation of the tangent to the head curve in the initialization point
-      head = homotopy(if s > 0 then (N/N_nominal)^2*flowCharacteristic(V_flow_single*N_nominal/N)
+      // or the zero-flow vertical axis in case the system is initialized with the check valve closed
+      if checkValveHomotopy == Types.CheckValveHomotopyType.NoHomotopy then
+        head = if s > 0 then (N/N_nominal)^2*flowCharacteristic(V_flow_single*N_nominal/N)
+                               else (N/N_nominal)^2*flowCharacteristic(0) - s*unitHead;
+        V_flow_single = if s > 0 then s*unitMassFlowRate/rho else 0;
+      else
+        head = homotopy(if s > 0 then (N/N_nominal)^2*flowCharacteristic(V_flow_single*N_nominal/N)
                                else (N/N_nominal)^2*flowCharacteristic(0) - s*unitHead,
-                      N/N_nominal*(flowCharacteristic(V_flow_single_init)+(V_flow_single-V_flow_single_init)*noEvent(if abs(V_flow_single_init)>0 then delta_head_init/(0.1*V_flow_single_init) else 0)));
-      V_flow_single = homotopy(if s > 0 then s*unitMassFlowRate/rho else 0,
-                               s*unitMassFlowRate/rho_nominal);
+                      if checkValveHomotopy == Types.CheckValveHomotopyType.Open then
+                        N/N_nominal*(flowCharacteristic(V_flow_single_init)+(V_flow_single-V_flow_single_init)*noEvent(if abs(V_flow_single_init)>0 then delta_head_init/(0.1*V_flow_single_init) else 0))
+                      else
+                        N/N_nominal*flowCharacteristic(0) - s*unitHead);
+        V_flow_single = homotopy(if s > 0 then s*unitMassFlowRate/rho else 0,
+                               if checkValveHomotopy == Types.CheckValveHomotopyType.Open then s*unitMassFlowRate/rho_nominal else 0);
+      end if;
     end if;
     // Power consumption
     if use_powerCharacteristic then

diff --git a/Modelica/Fluid/Types.mo b/Modelica/Fluid/Types.mo
@@ -318,6 +318,13 @@ ModelStructure.a_vb).
 
 </html>"));
 
+  type CheckValveHomotopyType = enumeration(Open, Closed, NoHomotopy)
+   "Enumeration with choices for check valve homotopy"
+    annotation (Documentation(info="<html>
+    <p>If it is know whether the check valve will start open or closed this can simplify the initialization.</p>
+    <p>The choice <strong>NoHomotopy</strong> is useful if nothing is known for the check valve.</p>
+    </html>"));
+
   annotation (preferredView="info",
               Documentation(info="<html>