Numerical simulation of flushing effect on sewer sediments and comparison of four sediment transport formulas

Abstract

Results of numerical modeling of sediment flushing in a combined sewer reach are herein presented. Simulations were performed by using a numerical model based on the solution of the De SaintVenant–Exner equations by the TVD MacCormack scheme. The model, previously validated by means of data derived from laboratory experiments, was applied to the Lacassagne trunk sewer in Lyon, France. A Hydrass flushing gate was put into operation at this site in 2003 to remove sediments accumulated during 3 years. A 5-month long experimental campaign was carried out to measure the sediment profile evolution during flushing operations. Four sediment transport formulas were used for the numerical simulations and compared. The model proved to be able to reproduce correctly the global evolution of the sediment profiles as a function of the number of flushing operations.

Keywords:

• Combined sewer
• flushing
• modeling
• sediment transport
• sewer cleansing
• unsteady flow