A numerical study on waste transport in main drain

Abstract

IN the present study, the complex transient free surface flow in the maind drain is modelled by using a particle-based computational fluid dynamic method to investigate the effects of the geometry of the elbow at a stack's base and slope on the waste transport performance of the main drain. Annular inflow boundary condition is imposed at the upstream end of the elbows to model the water curtain formed by a typical downflow in the vertical stacks. As the first step on the study of the self-cleaning performance, instead of solid waste, sludge modelled as denser and more viscous fluid is considered. Despite its simplicity, the introduction of the mixable multiphase flow approach provides relevant insights about the waste transport performance, and the results show that the sequence of two 45° elbows and the 90° elbow with long radius, and the effects of the slope is negligible mainly in the initial phase of the waste transport.