functionpowerLaw_dp_der2
2nd derivative of function that computes mass flow rate for given pressure drop
Extends from Modelica.Icons.Function (Icon for functions).
Information
Function that implements the second order derivative of
Buildings.Fluid.BaseClasses.FlowModels.powerLaw_dp
with respect to the pressure difference dp,
assuming constant flow coefficients.
When called with dp_der=der(dp) and dp_der2=der(dp_der),
this function returns the second order derivative of m_flow
with respect to time.
When called with dp_der=1 and dp_der2=0,
this function returns the second order derivative of m_flow
with respect to dp.
Inputs
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Units.SI.PressureDifference | dp | Pressure difference | |
| Real | k | Flow coefficient, k = m_flow/ dp^(1/n) | |
| Real | n | Flow exponent, n=1 for laminar, n=2 for turbulent | |
| Modelica.Units.SI.MassFlowRate | m_flow_turbulent | Mass flow rate where transition to turbulent flow occurs | |
| Modelica.Units.SI.PressureDifference | dp_turbulent | Pressure difference where turbulent flow occurs | |
| Real | m | Flow exponent for the pressure drop | |
| Real | a1 | Polynomial coefficient for regularized implementation of flow resistance | |
| Real | a3 | Polynomial coefficient for regularized implementation of flow resistance | |
| Real | a5 | Polynomial coefficient for regularized implementation of flow resistance | |
| Real | C | Coefficient 1/k^n, based on the definition k = m_flow / dp^(1/n) | |
| Real | b1 | Polynomial coefficient for regularized implementation of flow resistance | |
| Real | b3 | Polynomial coefficient for regularized implementation of flow resistance | |
| Real | b5 | Polynomial coefficient for regularized implementation of flow resistance | |
| Real | dp_der | 1st derivative of pressure difference | |
| Real | dp_der2 | 2nd derivative of pressure difference |
Outputs
| Type | Name | Default | Description |
|---|---|---|---|
| Real | m_flow_der2 | 2nd derivative of mass flow rate in design flow direction |
Revisions
-
May 30, 2026, by Michael Wetter:
First implementation.
This is for Buildings, #4620.