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

Calculation of the local pressure loss at a sudden change of the cross sectional areas (sudden expansion or sudden contraction) with sharp corners at turbulent flow regime for incompressible and single-phase fluid flow through arbitrary shaped cross sectional area (square, circular, etc.) considering a smooth surface. The flow direction determines the type of the transition. In case of the design flow a sudden expansion will be considered. At flow reversal a sudden contraction will be considered.

Generally this function is numerically best used for the incompressible case, where the mass flow rate (m_flow) is known (as state variable) in the used model and the corresponding pressure loss (DP) has to be calculated. On the other hand the function dp_suddenChange_MFLOW is numerically best used for the compressible case if the pressure loss (dp) is known (out of pressures as state variable) and the mass flow rate (M_FLOW) has to be calculated. See more information.