Robust numerical treatment of flow transitions at drainage pipe boundaries

The present report describes a comprehensive modelling framework developed to handle flow transitions within drainage pipes and at their boundaries. The proposed numerical scheme is based on a finite volume formulation. Detailed specifications of boundary conditions at pipe ends are provided, along with a decision tree allowing to seamlessly manage transitions such as flow reversal, entrance drowning, or hydraulic jump migration through the boundaries. Proof-of-concept examples and comparison with laboratory data are given to illustrate the robustness of the proposed approach.