BuildSysPro.IBPSA.Fluid.BaseClasses.FlowModels.basicFlowFunction_dp_der2

# .BuildSysPro.IBPSA.Fluid.BaseClasses.FlowModels.basicFlowFunction_dp_der2

2nd derivative of flow function2nd derivative of function that computes mass flow rate for given pressure drop

## Information

Function that implements the second order derivative of IBPSA.Fluid.BaseClasses.FlowModels.basicFlowFunction_dp with respect to the mass flow rate.

#### Interface

>     function basicFlowFunction_dp_der2
>       extends Modelica.Icons.Function;
>       input Modelica.Units.SI.PressureDifference dp(displayUnit = "Pa") "Pressure difference between port_a and port_b (= port_a.p - port_b.p)";
>       input Real k(min = 0, unit = "") "Flow coefficient, k=m_flow/sqrt(dp), with unit=(kg.m)^(1/2)";
>       input Modelica.Units.SI.MassFlowRate m_flow_turbulent(min = 0) "Mass flow rate where transition to turbulent flow occurs";
>       input Real dp_der "1st derivative of pressure difference between port_a and port_b (= port_a.p - port_b.p)";
>       input Real dp_der2 "2nd derivative of pressure difference between port_a and port_b (= port_a.p - port_b.p)";
>       output Real m_flow_der2 "2nd derivative of mass flow rate in design flow direction";
>     end basicFlowFunction_dp_der2;

## Revisions

- January 4, 2019, by Michael Wetter:
  Set `Inline=false`.
  See #1070.
- May 1, 2017, by Filip Jorissen:
  Revised implementation such that IBPSA.Fluid.BaseClasses.FlowModels.basicFlowFunction_dp is C2 continuous. See #725.
- January 22, 2016, by Michael Wetter:
  Corrected type declaration of pressure difference. This is for #404.
- July 29, 2015, by Michael Wetter:
  First implementation to avoid in Dymola 2016 the warning "Differentiating ... under the assumption that it is continuous at switching".

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