This information is part of the Modelica Standard Library maintained by the Modelica Association.

Definition of relationship between pressure drop and volume flow rate:

• -V_flowLaminar < VolumeFlow < +V_flowLaminar: laminar, i.e., linear dependency of pressure drop on volume flow.
• -V_flowLaminar > VolumeFlow or VolumeFlow < +V_flowLaminar: turbulent, i.e., quadratic dependency of pressure drop on volume flow.

Linear and quadratic dependency are coupled smoothly at V_flowLaminar / dpLaminar. Quadratic dependency is defined by nominal volume flow and pressure drop (V_flowNominal / dpNominal). See also sketch at diagram layer.

V_flowLaminar	Value: Type: VolumeFlowRate (m³/s) Description: Laminar volume flow
dpLaminar	Value: Type: Pressure (Pa) Description: Laminar pressure drop
V_flowNominal	Value: Type: VolumeFlowRate (m³/s) Description: Nominal volume flow
dpNominal	Value: Type: Pressure (Pa) Description: Nominal pressure drop
frictionLoss	Value: 0 Type: Real Description: Part of friction losses fed to medium