Experimental and Numerical Investigation of Sediment Transport in Sewers

Abstract

Sewer sediment deposition represents a crucial aspect of the maintenance of wastewater systems and has negative effects on the system itself as well as the environment. Therefore, it is important to design combined sewers, as sewage collection systems with high deposition risk, with adequate self-cleansing velocity to avoid the deposition. Despite the large number of investigations, the lack of knowledge about the particle behaviour in sewers remains a major problem in the field of sewer management. In the present work, the transport of sediments in partially filled channels is investigated experimentally and the results are compared to 3D-simulations performed with a coupled Computational Fluid Dynamics (CFD) model and Discrete Element Method (DEM). This research aims to investigate the self-cleansing design concept for uniform non-cohesive sediments based on moving of existing sediments on the sewer bed. The CFD part of the simulation is carried out in the commercial CFD software ANSYS Fluent, which is two-way coupled to the commercial DEM software EDEM through its User Defined Function. EDEM enhances the particle handling capability by resolving particle contacts, modelling bonded particles and non-spherical particles. The multiphase model Volume of Fluid (VOF) is used to capture the water and air interaction and the Discrete Phase Model (DPM) is applied to track the injected EDEM-particles. This paper also examines the applicability and limitations of this coupling method in simulation of sewer systems.