Coupling acoustic devices for monitoring combined sewer network sediment deposits
Résumé
Combined sewer networks present unique features that are not well reproducible in laboratory and yet far to be understood. The transport of organic and mobile sediments, present in large quantities despite optimal design practices, dramatically changes the sewer flow features and interaction between flow and sediment. Hence, to understand both flow patterns and transport features of these complex environments, it is necessary to install in-situ instrumentation. In this paper, two different acoustic techniques are coupled to measure both the sediment interface and the velocity. In this case, a 2 MHz rotating head acoustic profiler and a 10 MHz Acoustic Doppler Velocimeter (ADV) have been installed together to survey both the position of sediment deposits and to measure velocity patterns. The results will compare measurements obtained in different environments, in which both coarser and finer and softer deposits are present. The results generally show a good agreement between the interfaces detected using the velocity measurements on coarse deposits, while the presence of soft deposits highlights the need of coupling measurements techniques that correctly asses the sediment interface.