DORA Algorithm for Network Flow Models with Improved Stability and Convergence Properties

A new methodology for the solution of shallow water equations is applied for the computation of the unsteady-state flow in an urban drainage network. The inertial terms are neglected in the momentum equations and the solution is decoupled into one kinematic and one diffusive component. After a short presentation of the DORA (Double ORder Approximation) methodology in the case of a single open channel, the new methodology is applied to the case of a sewer network. The transition from partial to full section and vice versa is treated without the help of the Preissmann approximation. The algorithm also allows the computation of the diffusive component in the case of vertical topographic discontinuities, without the introduction of any internal boundary conditions and without any change in the structure of the linear system matrix. The algorithm is tested on one field example, and its performance is compared with the performance of other popular commercial codes.