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 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. On the other hand the function dp_suddenChange_DP 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. See more information.