Merge pull request #1466 from open-ideas/ibpsa_merged

IBPSA merge

Author: jelgerjansen

IDEAS/.copiedFiles.txt

@@ -4,6 +4,7 @@ IDEAS\Airflow\Multizone\BaseClasses\Door.mo
 IDEAS\Airflow\Multizone\BaseClasses\DoorDiscretized.mo
 IDEAS\Airflow\Multizone\BaseClasses\ErrorControl.mo
 IDEAS\Airflow\Multizone\BaseClasses\Examples\PowerLaw.mo
+IDEAS\Airflow\Multizone\BaseClasses\Examples\PowerLaw05.mo
 IDEAS\Airflow\Multizone\BaseClasses\Examples\PowerLawFixedM.mo
 IDEAS\Airflow\Multizone\BaseClasses\Examples\WindPressureLowRise.mo
 IDEAS\Airflow\Multizone\BaseClasses\Examples\WindPressureProfile.mo
@@ -17,6 +18,7 @@ IDEAS\Airflow\Multizone\BaseClasses\ZonalFlow.mo
 IDEAS\Airflow\Multizone\BaseClasses\package.mo
 IDEAS\Airflow\Multizone\BaseClasses\package.order
 IDEAS\Airflow\Multizone\BaseClasses\powerLaw.mo
+IDEAS\Airflow\Multizone\BaseClasses\powerLaw05.mo
 IDEAS\Airflow\Multizone\BaseClasses\powerLawFixedM.mo
 IDEAS\Airflow\Multizone\BaseClasses\windPressureLowRise.mo
 IDEAS\Airflow\Multizone\BaseClasses\windPressureProfile.mo
@@ -2912,6 +2914,7 @@ IDEAS\Resources\Images\Utilities\Math\int.pdf
 IDEAS\Resources\Images\Utilities\Math\int.png
 IDEAS\Resources\Python-Sources\MakeORCFluidRecord.py
 IDEAS\Resources\ReferenceResults\Dymola\IDEAS_Airflow_Multizone_BaseClasses_Examples_PowerLaw.txt
+IDEAS\Resources\ReferenceResults\Dymola\IDEAS_Airflow_Multizone_BaseClasses_Examples_PowerLaw05.txt
 IDEAS\Resources\ReferenceResults\Dymola\IDEAS_Airflow_Multizone_BaseClasses_Examples_PowerLawFixedM.txt
 IDEAS\Resources\ReferenceResults\Dymola\IDEAS_Airflow_Multizone_BaseClasses_Examples_WindPressureLowRise.txt
 IDEAS\Resources\ReferenceResults\Dymola\IDEAS_Airflow_Multizone_BaseClasses_Examples_WindPressureProfile.txt
@@ -3824,6 +3827,7 @@ IDEAS\Resources\ReferenceResults\Dymola\IDEAS_Utilities_Time_Validation_Calendar
 IDEAS\Resources\ReferenceResults\Dymola\IDEAS_Utilities_Time_Validation_CalendarTimeMonthsMinus.txt
 IDEAS\Resources\ReferenceResults\Dymola\IDEAS_Utilities_Time_Validation_CalendarTimeMonthsPlus.txt
 IDEAS\Resources\Scripts\Dymola\Airflow\Multizone\BaseClasses\Examples\PowerLaw.mos
+IDEAS\Resources\Scripts\Dymola\Airflow\Multizone\BaseClasses\Examples\PowerLaw05.mos
 IDEAS\Resources\Scripts\Dymola\Airflow\Multizone\BaseClasses\Examples\PowerLawFixedM.mos
 IDEAS\Resources\Scripts\Dymola\Airflow\Multizone\BaseClasses\Examples\WindPressureLowRise.mos
 IDEAS\Resources\Scripts\Dymola\Airflow\Multizone\BaseClasses\Examples\WindPressureProfile.mos
@@ -4743,6 +4747,46 @@ IDEAS\Resources\src\convertEPW\src\ConvertWeatherData.java
 IDEAS\Resources\src\convertEPW\src\Makefile
 IDEAS\Resources\src\convertEPW\src\Manifest.txt
 IDEAS\Resources\src\fluid\heatpumps\calibration\Examples\SomeManufacturer_ABC060_70kW_4_0COP_R410A.mo
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootstrap-3.4.1\css\bootstrap-theme.css
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootstrap-3.4.1\css\bootstrap-theme.css.map
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootstrap-3.4.1\css\bootstrap-theme.min.css
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootstrap-3.4.1\css\bootstrap-theme.min.css.map
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootstrap-3.4.1\css\bootstrap.css
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootstrap-3.4.1\css\bootstrap.css.map
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootstrap-3.4.1\css\bootstrap.min.css
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootstrap-3.4.1\css\bootstrap.min.css.map
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootstrap-3.4.1\fonts\glyphicons-halflings-regular.eot
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootstrap-3.4.1\fonts\glyphicons-halflings-regular.svg
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootstrap-3.4.1\fonts\glyphicons-halflings-regular.ttf
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootstrap-3.4.1\fonts\glyphicons-halflings-regular.woff
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootstrap-3.4.1\fonts\glyphicons-halflings-regular.woff2
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootstrap-3.4.1\js\bootstrap.js
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootstrap-3.4.1\js\bootstrap.min.js
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootstrap-3.4.1\js\npm.js
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootswatch-3.4.1\cerulean\bootstrap.min.css
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootswatch-3.4.1\cosmo\bootstrap.min.css
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootswatch-3.4.1\cyborg\bootstrap.min.css
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootswatch-3.4.1\darkly\bootstrap.min.css
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootswatch-3.4.1\flatly\bootstrap.min.css
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootswatch-3.4.1\fonts\glyphicons-halflings-regular.eot
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootswatch-3.4.1\fonts\glyphicons-halflings-regular.svg
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootswatch-3.4.1\fonts\glyphicons-halflings-regular.ttf
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootswatch-3.4.1\fonts\glyphicons-halflings-regular.woff
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootswatch-3.4.1\fonts\glyphicons-halflings-regular.woff2
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootswatch-3.4.1\journal\bootstrap.min.css
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootswatch-3.4.1\lumen\bootstrap.min.css
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootswatch-3.4.1\paper\bootstrap.min.css
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootswatch-3.4.1\readable\bootstrap.min.css
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootswatch-3.4.1\sandstone\bootstrap.min.css
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootswatch-3.4.1\simplex\bootstrap.min.css
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootswatch-3.4.1\slate\bootstrap.min.css
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootswatch-3.4.1\spacelab\bootstrap.min.css
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootswatch-3.4.1\superhero\bootstrap.min.css
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootswatch-3.4.1\united\bootstrap.min.css
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\bootswatch-3.4.1\yeti\bootstrap.min.css
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\jquery-3.5.1.js
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\js\jquery-1.12.4.min.js
+IDEAS\Resources\src\fluid\heatpumps\calibration\doc\build\html\_static\underscore-1.13.1.js
 IDEAS\Resources\weatherdata\DRYCOLD.TMY
 IDEAS\Resources\weatherdata\DRYCOLD.mos
 IDEAS\Resources\weatherdata\USA_CA_San.Francisco.Intl.AP.724940_TMY3.epw

IDEAS/Airflow/Multizone/BaseClasses/Door.mo

@@ -43,6 +43,9 @@ protected
   constant Real conTP = IDEAS.Media.Air.dStp*Modelica.Media.IdealGases.Common.SingleGasesData.Air.R_s
     "Conversion factor for converting temperature difference to pressure difference";
 
+  final parameter Real sqrt_dp_turbulent(min=0) = sqrt(dp_turbulent)
+    "Square root of pressure difference where laminar and turbulent flow relation coincide";
+
   parameter Medium.ThermodynamicState sta_default=Medium.setState_pTX(
       T=Medium.T_default,
       p=Medium.p_default,
@@ -118,6 +121,13 @@ This is a partial model for the bi-directional air flow through a door.
 revisions="<html>
 <ul>
 <li>
+September 19, 2025, by Michael Wetter:<br/>
+Introduced protected parameter <code>sqrt_dp_turbulent</code>,
+which is needed to improve computing efficiency if flow exponent is <i>0.5</i>.<br/>
+This is for
+<a href=\"https://github.com/ibpsa/modelica-ibpsa/issues/2043\">IBPSA, #2043</a>.
+</li>
+<li>
 October 6, 2020, by Michael Wetter:<br/>
 First implementation for
 <a href=\"https://github.com/ibpsa/modelica-ibpsa/issues/1353\">#1353</a>.

IDEAS/Airflow/Multizone/BaseClasses/DoorDiscretized.mo

@@ -28,6 +28,9 @@ protected
   parameter Modelica.Units.SI.Density rho_default=Medium.density(sta_default)
     "Density, used to compute fluid volume";
 
+  final parameter Real sqrt_dp_turbulent(min=0) = sqrt(dp_turbulent)
+    "Square root of pressure difference where laminar and turbulent flow relation coincide";
+
   input Real hAg[nCom](each unit="m2/s2")=
     {Modelica.Constants.g_n*(hA - (i - 0.5)*dh) for i in 1:nCom}
     "Product g*h_i for each compartment";
@@ -118,6 +121,13 @@ using the model for a door that can be open or closed.
 revisions="<html>
 <ul>
 <li>
+September 19, 2025, by Michael Wetter:<br/>
+Introduced protected parameter <code>sqrt_dp_turbulent</code>,
+which is needed to improve computing efficiency if flow exponent is <i>0.5</i>.<br/>
+This is for
+<a href=\"https://github.com/ibpsa/modelica-ibpsa/issues/2043\">IBPSA, #2043</a>.
+</li>
+<li>
 October 29, 2024, by Klaas De Jonge:<br/>
 Unprotected <code>dh</code> and changed prefixes of <code>dh</code>,<code>hAg</code> and <code>hBg</code> to <code>input</code>.<br/>
 This is for <a href=\"https://github.com/ibpsa/modelica-ibpsa/issues/1935\">#1935</a>.

IDEAS/Airflow/Multizone/BaseClasses/Examples/PowerLaw05.mo

@@ -0,0 +1,73 @@
+within IDEAS.Airflow.Multizone.BaseClasses.Examples;
+model PowerLaw05
+  "Test model for power law function with constant exponent of 0.5"
+  extends Modelica.Icons.Example;
+  parameter Real C = 2/10^m "Flow coefficient, C = V_flow/ dp^m";
+
+  constant Real m(min=0.5, max=1) = 0.5
+    "Flow exponent, m=0.5 for turbulent, m=1 for laminar";
+  parameter Modelica.Units.SI.PressureDifference dp_turbulent(min=0) = 5
+    "Pressure difference where regularization starts";
+  final parameter Real sqrt_dp_turbulent(min=0) = sqrt(dp_turbulent)
+    "Square root of pressure difference where regularization starts";
+
+  Modelica.Units.SI.PressureDifference dp "Pressure difference";
+  Modelica.Units.SI.VolumeFlowRate V_flow
+    "Volume flow rate computed with model powerLaw";
+  Modelica.Units.SI.VolumeFlowRate VFixed_flow
+    "Volume flow rate computed with model powerLawFixed";
+
+  constant Real gamma(min=1) = 1.5
+    "Normalized flow rate where dphi(0)/dpi intersects phi(1)";
+  constant Real a = gamma
+    "Polynomial coefficient for regularized implementation of flow resistance";
+  constant Real b = 1/8*m^2 - 3*gamma - 3/2*m + 35.0/8
+    "Polynomial coefficient for regularized implementation of flow resistance";
+  constant Real c = -1/4*m^2 + 3*gamma + 5/2*m - 21.0/4
+    "Polynomial coefficient for regularized implementation of flow resistance";
+  constant Real d = 1/8*m^2 - gamma - m + 15.0/8
+    "Polynomial coefficient for regularized implementation of flow resistance";
+
+equation
+  dp = 10*(-1+2*time);
+  V_flow = IDEAS.Airflow.Multizone.BaseClasses.powerLaw(
+    dp=dp,
+    C=C,
+    m=m,
+    dp_turbulent=dp_turbulent);
+  VFixed_flow = IDEAS.Airflow.Multizone.BaseClasses.powerLaw05(
+    C=C,
+    dp=dp,
+    a=a,
+    b=b,
+    c=c,
+    d=d,
+    dp_turbulent=dp_turbulent,
+    sqrt_dp_turbulent=sqrt_dp_turbulent);
+  assert(abs(V_flow-VFixed_flow) < 1E-10, "Error: The two implementations of the power law model need to give identical results");
+  annotation (
+experiment(Tolerance=1e-6, StopTime=1.0),
+  __Dymola_Commands(file="modelica://IDEAS/Resources/Scripts/Dymola/Airflow/Multizone/BaseClasses/Examples/PowerLaw05.mos"
+        "Simulate and plot"), Documentation(info="<html>
+<p>
+This examples demonstrates the
+<a href=\"modelica://IDEAS.Airflow.Multizone.BaseClasses.powerLaw\">
+IDEAS.Airflow.Multizone.BaseClasses.powerLaw</a>
+and
+<a href=\"modelica://IDEAS.Airflow.Multizone.BaseClasses.powerLaw05\">
+IDEAS.Airflow.Multizone.BaseClasses.powerLaw05</a>
+functions.
+They need to return the same function value.
+This is verified by an <code>assert</code> statement.
+</p>
+</html>", revisions="<html>
+<ul>
+<li>
+September 19. 2025, by Michael Wetter:<br/>
+First implementation.<br/>
+This is for
+<a href=\"https://github.com/ibpsa/modelica-ibpsa/issues/2043\">IBPSA, #2043</a>.
+</li>
+</ul>
+</html>"));
+end PowerLaw05;

IDEAS/Airflow/Multizone/BaseClasses/Examples/package.order

@@ -1,5 +1,6 @@
 Interpolate
 PowerLaw
+PowerLaw05
 PowerLawFixedM
 WindPressureLowRise
 WindPressureProfile

IDEAS/Airflow/Multizone/BaseClasses/PartialOneWayFlowElement.mo

@@ -31,13 +31,15 @@ protected
     Medium.dynamicViscosity(sta_default)
     "Dynamic viscosity at the medium default properties";
 
+  final parameter Real sqrt_dp_turbulent(min=0) = sqrt(dp_turbulent)
+    "Square root of pressure difference where laminar and turbulent flow relation coincide";
+
   Medium.ThermodynamicState sta "State of the medium in the component";
   Modelica.Units.SI.DynamicViscosity dynVis "Dynamic viscosity";
-  Real mExc(quantity="Mass", final unit="kg")
+  Modelica.Units.SI.Mass mExc(start=0, fixed=true, unbounded=true)
     "Air mass exchanged (for purpose of error control only)";
 
 initial equation
-  mExc=0;
   assert(homotopyInitialization, "In " + getInstanceName() +
     ": The constant homotopyInitialization has been modified from its default value. This constant will be removed in future releases.",
     level = AssertionLevel.warning);
@@ -110,6 +112,25 @@ not in the equation section since this model sets both
 revisions="<html>
 <ul>
 <li>
+September 22, 2025, by Michael Wetter:<br/>
+Set <code>unbounded=true</code> for <code>mExc_flow</code>.
+This is to have the same implementation as in
+<a href=\"modelica://IDEAS.Airflow.Multizone.BaseClasses.TwoWayFlowElement\">
+IDEAS.Airflow.Multizone.BaseClasses.TwoWayFlowElement</a>
+where this change was done to avoid spikes in <code>port_a.m_flow</code> in
+<a href=\"modelica://IDEAS.Airflow.Multizone.Examples.OneOpenDoor\">
+IDEAS.Airflow.Multizone.Examples.OneOpenDoor</a>.<br/>
+This is for
+<a href=\"https://github.com/lbl-srg/modelica-buildings/issues/4360\">Buildings, #4360</a>.
+</li>
+<li>
+September 19, 2025, by Michael Wetter:<br/>
+Introduced protected parameter <code>sqrt_dp_turbulent</code>,
+which is needed to improve computing efficiency if flow exponent is <i>0.5</i>.<br/>
+This is for
+<a href=\"https://github.com/ibpsa/modelica-ibpsa/issues/2043\">IBPSA, #2043</a>.
+</li>
+<li>
 February 2, 2022, by Michael Wetter:<br/>
 Revised implementation.<br/>
 This is for

IDEAS/Airflow/Multizone/BaseClasses/TwoWayFlowElement.mo

@@ -41,9 +41,9 @@ protected
   Modelica.Units.SI.VolumeFlowRate VZer_flow(fixed=false)
     "Minimum net volume flow rate to prevent zero flow";
 
-  Modelica.Units.SI.Mass mExcAB(start=0, fixed=true)
+  Modelica.Units.SI.Mass mExcAB(start=0, fixed=true, unbounded=true)
     "Air mass exchanged (for purpose of error control only)";
-  Modelica.Units.SI.Mass mExcBA(start=0, fixed=true)
+  Modelica.Units.SI.Mass mExcBA(start=0, fixed=true, unbounded=true)
     "Air mass exchanged (for purpose of error control only)";
 
   Medium.MassFraction Xi_a1_inflow[Medium1.nXi]
@@ -55,8 +55,8 @@ equation
   // gives higher robustness. The reason may be that for bi-directional flow,
   // (VAB_flow - VBA_flow) may be close to zero.
   if forceErrorControlOnFlow then
-    der(mExcAB) = mAB_flow;
-    der(mExcBA) = mBA_flow;
+    der(mExcAB) = port_a1.m_flow;
+    der(mExcBA) = port_a2.m_flow;
   else
     der(mExcAB) = 0;
     der(mExcBA) = 0;
@@ -82,14 +82,14 @@ equation
 
   VZer_flow = vZer*A;
 
-  mAB_flow = rho_a1_inflow*VAB_flow;
-  mBA_flow = rho_a2_inflow*VBA_flow;
+  mAB_flow = port_a1.m_flow;
+  mBA_flow = port_a2.m_flow;
   // Average velocity (using the whole orifice area)
   vAB = VAB_flow/A;
   vBA = VBA_flow/A;
 
-  port_a1.m_flow = mAB_flow;
-  port_a2.m_flow = mBA_flow;
+  port_a1.m_flow = rho_a1_inflow*VAB_flow;
+  port_a2.m_flow = rho_a2_inflow*VBA_flow;
 
   // Energy balance (no storage, no heat loss/gain)
   port_a1.h_outflow = inStream(port_b1.h_outflow);
@@ -135,6 +135,26 @@ for doors that can be open or closed as a function of an input signal.
 revisions="<html>
 <ul>
 <li>
+September 22, 2025, by Michael Wetter:<br/>
+Set <code>unbounded=true</code> for <code>mExcAB_flow</code> and <code>mExcBA_flow</code>
+to avoid spikes in <code>port_a.m_flow</code> in
+<a href=\"modelica://IDEAS.Airflow.Multizone.Examples.OneOpenDoor\">
+IDEAS.Airflow.Multizone.Examples.OneOpenDoor</a>.<br/>
+This is for
+<a href=\"https://github.com/lbl-srg/modelica-buildings/issues/4360\">Buildings, #4360</a>.
+</li>
+<li>
+September 19, 2025, by Michael Wetter:<br/>
+Refactored implementation of underlying function that computes the flow rate
+to allow function to be inlined.
+This leads to a 20% faster simulation of
+<a href=\"modelica://IDEAS.Airflow.Multizone.Examples.OneOpenDoor\">
+IDEAS.Airflow.Multizone.Examples.OneOpenDoor</a> compared to the previous
+implementation.<br/>
+This is for
+<a href=\"https://github.com/ibpsa/modelica-ibpsa/issues/2043\">IBPSA, #2043</a>.
+</li>
+<li>
 May 12, 2020, by Michael Wetter:<br/>
 Changed assignment of <code>m1_flow_small</code> and
 <code>m2_flow_small</code> to <code>final</code>.

IDEAS/Airflow/Multizone/BaseClasses/package.order

@@ -8,6 +8,7 @@ TwoWayFlowElementBuoyancy
 ZonalFlow
 interpolate
 powerLaw
+powerLaw05
 powerLawFixedM
 windPressureLowRise
 windPressureProfile

IDEAS/Airflow/Multizone/BaseClasses/powerLaw.mo

@@ -14,32 +14,31 @@ function powerLaw "Power law used in orifice equations"
 protected
   constant Real gamma(min=1) = 1.5
     "Normalized flow rate where dphi(0)/dpi intersects phi(1)";
-  Real a
-    "Polynomial coefficient for regularized implementation of flow resistance";
-  Real b
-    "Polynomial coefficient for regularized implementation of flow resistance";
-  Real c
-    "Polynomial coefficient for regularized implementation of flow resistance";
-  Real d
-    "Polynomial coefficient for regularized implementation of flow resistance";
-  Real pi "Normalized pressure";
-  Real pi2 "Square of normalized pressure";
+  Real pi = dp/dp_turbulent "Normalized pressure";
+  Real pi2 = pi*pi "Square of normalized pressure";
 algorithm
- if (dp >= dp_turbulent) then
-   V_flow :=C *dp^m;
+ V_flow := if (dp >= dp_turbulent) then
+   C *dp^m
  elseif (dp <= -dp_turbulent) then
-   V_flow :=-C*(-dp)^m;
+   -C*(-dp)^m
  else
+   C *dp_turbulent^m * pi *
+     ( gamma + pi2 *
+     ( (1/8*m^2 - 3*gamma - 3/2*m + 35.0/8) + pi2 *
+     ( (-1/4*m^2 + 3*gamma + 5/2*m - 21.0/4) + pi2 *
+     (1/8*m^2 - gamma - m + 15.0/8))));
+   /*
    a := gamma;
    b := 1/8*m^2 - 3*gamma - 3/2*m + 35.0/8;
    c := -1/4*m^2 + 3*gamma + 5/2*m - 21.0/4;
    d := 1/8*m^2 - gamma - m + 15.0/8;
-   pi  := dp/dp_turbulent;
-   pi2 := pi*pi;
    V_flow :=C *dp_turbulent^m * pi * ( a + pi2 * ( b + pi2 * ( c + pi2 * d)));
- end if;
+   */
 
-  annotation (smoothOrder=2,
+
+  annotation (
+  smoothOrder=2,
+  Inline=true,
 Documentation(info="<html>
 <p>
 This model describes the mass flow rate and pressure difference relation
@@ -82,6 +81,16 @@ of a model.
 revisions="<html>
 <ul>
 <li>
+September 19, 2025, by Michael Wetter:<br/>
+Refactored implementation to allow function to be inlined.
+This leads to a 20% faster simulation of
+<a href=\"modelica://IDEAS.Airflow.Multizone.Examples.OneOpenDoor\">
+IDEAS.Airflow.Multizone.Examples.OneOpenDoor</a> compared to the previous
+implementation.<br/>
+This is for
+<a href=\"https://github.com/ibpsa/modelica-ibpsa/issues/2043\">IBPSA, #2043</a>.
+</li>
+<li>
 February 8, 2022, by Michael Wetter:<br/>
 Changed to use <code>C</code> for volume flow coefficient (<i>C = V_flow/dp^m</i>),
 and <code>k</code> for mass flow coefficient (<i>k = m_flow/dp^m</i>).