diff --git a/IBPSA/Fluid/BaseClasses/FlowModels/Validation/BasicFlowFunction_dp_DerivativeCheck.mo b/IBPSA/Fluid/BaseClasses/FlowModels/Validation/BasicFlowFunction_dp_DerivativeCheck.mo
index fdcc56b385..e3f1c0903c 100644
--- a/IBPSA/Fluid/BaseClasses/FlowModels/Validation/BasicFlowFunction_dp_DerivativeCheck.mo
+++ b/IBPSA/Fluid/BaseClasses/FlowModels/Validation/BasicFlowFunction_dp_DerivativeCheck.mo
@@ -21,6 +21,7 @@ equation
k = k,
m_flow_turbulent=m_flow_turbulent);
der(m_flow) = der(m_flow_comp);
+ der_m_flow_dp = IBPSA.Fluid.BaseClasses.FlowModels.basicFlowFunction_dp_der(dp);
err = m_flow-m_flow_comp;
assert(abs(err) < 1E-3, "Error in implementation.");
annotation (
diff --git a/IBPSA/Fluid/BaseClasses/FlowModels/basicFlowFunction_dp_der.mo b/IBPSA/Fluid/BaseClasses/FlowModels/basicFlowFunction_dp_der.mo
index 335c0fa6cb..0777dbb0ab 100644
--- a/IBPSA/Fluid/BaseClasses/FlowModels/basicFlowFunction_dp_der.mo
+++ b/IBPSA/Fluid/BaseClasses/FlowModels/basicFlowFunction_dp_der.mo
@@ -31,7 +31,7 @@ Documentation(info="
Function that implements the first order derivative of
IBPSA.Fluid.BaseClasses.FlowModels.basicFlowFunction_dp
-with respect to the mass flow rate.
+with respect to time.
",
revisions="
diff --git a/IBPSA/Fluid/BaseClasses/FlowModels/basicFlowFunction_dp_der2.mo b/IBPSA/Fluid/BaseClasses/FlowModels/basicFlowFunction_dp_der2.mo
index e64a9fbdb6..cd405fe2c2 100644
--- a/IBPSA/Fluid/BaseClasses/FlowModels/basicFlowFunction_dp_der2.mo
+++ b/IBPSA/Fluid/BaseClasses/FlowModels/basicFlowFunction_dp_der2.mo
@@ -36,7 +36,7 @@ Documentation(info="
Function that implements the second order derivative of
IBPSA.Fluid.BaseClasses.FlowModels.basicFlowFunction_dp
-with respect to the mass flow rate.
+with respect to time.
",
revisions="
diff --git a/IBPSA/Fluid/BaseClasses/FlowModels/basicFlowFunction_m_flow_der.mo b/IBPSA/Fluid/BaseClasses/FlowModels/basicFlowFunction_m_flow_der.mo
index 05c27661a2..7169c2a5c4 100644
--- a/IBPSA/Fluid/BaseClasses/FlowModels/basicFlowFunction_m_flow_der.mo
+++ b/IBPSA/Fluid/BaseClasses/FlowModels/basicFlowFunction_m_flow_der.mo
@@ -32,7 +32,7 @@ Documentation(info="
Function that implements the first order derivative of
IBPSA.Fluid.BaseClasses.FlowModels.basicFlowFunction_m_flow
-with respect to the mass flow rate.
+with respect to time.
",
revisions="
diff --git a/IBPSA/Fluid/BaseClasses/FlowModels/basicFlowFunction_m_flow_der2.mo b/IBPSA/Fluid/BaseClasses/FlowModels/basicFlowFunction_m_flow_der2.mo
index 6c70c3ef0e..2b63cf1a76 100644
--- a/IBPSA/Fluid/BaseClasses/FlowModels/basicFlowFunction_m_flow_der2.mo
+++ b/IBPSA/Fluid/BaseClasses/FlowModels/basicFlowFunction_m_flow_der2.mo
@@ -36,7 +36,7 @@ Documentation(info="
Function that implements the second order derivative of
IBPSA.Fluid.BaseClasses.FlowModels.basicFlowFunction_m_flow
-with respect to the mass flow rate.
+with respect to time.
",
revisions="
diff --git a/IBPSA/Fluid/FixedResistances/CheckValve.mo b/IBPSA/Fluid/FixedResistances/CheckValve.mo
index 883f7acc25..6e5196f446 100644
--- a/IBPSA/Fluid/FixedResistances/CheckValve.mo
+++ b/IBPSA/Fluid/FixedResistances/CheckValve.mo
@@ -27,48 +27,75 @@ model CheckValve "Check valve that avoids flow reversal"
else 0
"Flow coefficient of fixed resistance that may be in series with valve,
k=m_flow/sqrt(dp), with unit=(kg.m)^(1/2).";
-
- Real k(min=Modelica.Constants.small)
- "Flow coefficient of valve and pipe in series in allowed/forward direction,
- k=m_flow/sqrt(dp), with unit=(kg.m)^(1/2).";
-
protected
- Real a
- "Scaled pressure variable";
- Real cv
- "Twice differentiable Heaviside check valve characteristic";
- Real kCv
- "Smoothed restriction characteristic";
-
+ parameter Real k_min=if dpFixed_nominal > Modelica.Constants.eps then
+ sqrt(1 / (1 / kFixed ^ 2 + 1 /(l * Kv_SI) ^ 2)) else l * Kv_SI
+ "Minimum flow coefficient (valve closed)";
+ parameter Real k_max=if dpFixed_nominal > Modelica.Constants.eps then
+ sqrt(1 / (1 / kFixed ^ 2 + 1 / Kv_SI ^ 2)) else Kv_SI
+ "Maximum flow coefficient (valve fully open)";
+ Modelica.Units.SI.MassFlowRate m_flow_min
+ "Flow rate through closed valve";
+ Modelica.Units.SI.MassFlowRate m_flow_max
+ "Flow rate through fully open valve";
+ Modelica.Units.SI.MassFlowRate m_flow_smooth
+ "Smooth interpolation result between two flow regimes";
initial equation
- assert(dpFixed_nominal > -Modelica.Constants.eps,
- "In " + getInstanceName() + ": We require dpFixed_nominal >= 0.
+ assert(dpFixed_nominal > - Modelica.Constants.eps, "In " + getInstanceName() +
+ ": We require dpFixed_nominal >= 0.
Received dpFixed_nominal = " + String(dpFixed_nominal) + " Pa.");
- assert(l > -Modelica.Constants.eps,
- "In " + getInstanceName() + ": We require l >= 0. Received l = " + String(l));
+ assert(l > - Modelica.Constants.eps, "In " + getInstanceName() +
+ ": We require l >= 0. Received l = " + String(l));
equation
- a = dp/dpValve_closing;
- cv = smooth(2, max(0, min(1, a^3*(10+a*(-15+6*a)))));
- kCv = Kv_SI*(cv*(1-l) + l);
-
- if (dpFixed_nominal > Modelica.Constants.eps) then
- k = sqrt(1/(1/kFixed^2 + 1/kCv^2));
- else
- k = kCv;
- end if;
-
+ // min function ensures that m_flow_y1 does not increase further for dp_x > dp_x1
+ m_flow_min=IBPSA.Fluid.BaseClasses.FlowModels.basicFlowFunction_dp(
+ dp=min(dp, 0),
+ k=k_min,
+ m_flow_turbulent=m_flow_turbulent);
+ // max function ensures that m_flow_y2 does not decrease further for dp_x < dp_x2
+ m_flow_max=IBPSA.Fluid.BaseClasses.FlowModels.basicFlowFunction_dp(
+ dp=max(dp, dpValve_closing),
+ k=k_max,
+ m_flow_turbulent=m_flow_turbulent);
+ // We compute d(m_flow)/dp by calling d(m_flow)/dt with dp/dt=1,
+ // and d2(m_flow)/dp2 by calling d2(m_flow)/dt2 with dp/dt=1 and d2p/dt2=0
+ m_flow_smooth=noEvent(smooth(2,
+ if dp <= 0 then m_flow_min
+ elseif dp >= dpValve_closing then m_flow_max
+ else IBPSA.Utilities.Math.Functions.quinticHermite(
+ x=dp,
+ x1=0,
+ x2=dpValve_closing,
+ y1=m_flow_min,
+ y2=m_flow_max,
+ y1d=IBPSA.Fluid.BaseClasses.FlowModels.basicFlowFunction_dp_der(
+ dp=0,
+ k=k_min,
+ m_flow_turbulent=m_flow_turbulent,
+ dp_der=1),
+ y2d=IBPSA.Fluid.BaseClasses.FlowModels.basicFlowFunction_dp_der(
+ dp=dpValve_closing,
+ k=k_max,
+ m_flow_turbulent=m_flow_turbulent,
+ dp_der=1),
+ y1dd=IBPSA.Fluid.BaseClasses.FlowModels.basicFlowFunction_dp_der2(
+ dp=0,
+ k=k_min,
+ m_flow_turbulent=m_flow_turbulent,
+ dp_der=1,
+ dp_der2=0),
+ y2dd=IBPSA.Fluid.BaseClasses.FlowModels.basicFlowFunction_dp_der2(
+ dp=dpValve_closing,
+ k=k_max,
+ m_flow_turbulent=m_flow_turbulent,
+ dp_der=1,
+ dp_der2=0))));
if homotopyInitialization then
- m_flow = homotopy(
- actual=IBPSA.Fluid.BaseClasses.FlowModels.basicFlowFunction_dp(
- dp = dp,
- k = k,
- m_flow_turbulent = m_flow_turbulent),
- simplified = m_flow_nominal_pos*dp/dp_nominal_pos);
+ m_flow=homotopy(
+ actual=m_flow_smooth,
+ simplified=m_flow_nominal_pos * dp / dp_nominal_pos);
else
- m_flow = IBPSA.Fluid.BaseClasses.FlowModels.basicFlowFunction_dp(
- dp = dp,
- k = k,
- m_flow_turbulent = m_flow_turbulent);
+ m_flow=m_flow_smooth;
end if;
annotation (Icon(coordinateSystem(preserveAspectRatio=true, extent={{-100,-100},
{100,100}}), graphics={
diff --git a/IBPSA/Resources/Scripts/Dymola/Fluid/FixedResistances/Examples/CheckValve.mos b/IBPSA/Resources/Scripts/Dymola/Fluid/FixedResistances/Examples/CheckValve.mos
index 30e334f42f..20327d0c8d 100644
--- a/IBPSA/Resources/Scripts/Dymola/Fluid/FixedResistances/Examples/CheckValve.mos
+++ b/IBPSA/Resources/Scripts/Dymola/Fluid/FixedResistances/Examples/CheckValve.mos
@@ -1,4 +1,3 @@
simulateModel("IBPSA.Fluid.FixedResistances.Examples.CheckValve", method="Cvode", tolerance=1e-06, stopTime=1, resultFile="CheckValve");
createPlot(id=1, position={0, 0, 988, 599}, y={"checkValve.dp", "checkValve_m_flow.dp"}, range={0.0, 1.0, -20000.0, 40000.0}, grid=true, colors={{28,108,200}, {238,46,47}});
createPlot(id=1, position={0, 0, 988, 197}, y={"checkValve.m_flow", "checkValveDpFix.m_flow", "checkValve_m_flow.m_flow"}, range={0.0, 1.0, -2.0, 6.0}, grid=true, subPlot=2, colors={{28,108,200}, {238,46,47}, {0,140,72}});
-createPlot(id=1, position={0, 0, 988, 197}, y={"checkValve.k", "checkValveDpFix.k", "checkValve_m_flow.k"}, range={0.0, 1.0, -0.02, 0.06}, grid=true, subPlot=3, colors={{28,108,200}, {238,46,47}, {0,140,72}});