A novel 1D-2D coupled model for hydrodynamic simulation of flows in drainage networks.

• A novel 1D-2D coupled model is developed for hydrodynamic simulation of transient flows in drainage networks. • The pipe flow is calculated using an improved 1D TPA model and the junction flow is approximated using a 2D hydrodynamic model. • The new approach automatically takes into account mass and momentum conservation in junction calculation and removes the necessity of complicated boundary settings. Drainage network modelling is often an essential component in urban flood prediction and risk assessment. Drainage network models most commonly use different numerical procedures to handle flows in pipes and junctions. Numerous numerical schemes and models of different levels of complexity have been developed and reported to predict flows in pipes. However, calculation of the flow conditions in junctions has received much less attention and has been traditionally achieved by solving only the continuity equation. This method is easy to implement but it neglects the momentum exchange in the junctions and cannot provide sufficient boundary conditions for the pipe calculation. In this work, a novel numerical scheme based on the finite volume solution to the two-dimensional (2D) shallow water equations (SWEs) is proposed to calculate flow dynamics in junctions, which directly takes into account both mass and momentum conservation and removes the necessity of implementing complicated boundary settings for pipe calculations. This new junction simulation method is then coupled with the widely used two-component pressure approach (TPA) for the pipe flow calculation, leading to a new integrated drainage network model. The new 1D-2D coupled drainage network model is validated against an experimental and several idealised test cases to demonstrate its potential for efficient and stable simulation of flow dynamics in drainage networks. [ABSTRACT FROM AUTHOR]