Laboratory measurements of the free surface profile were carried out over a physical model of a classical channel drop inserted in a sewer, equipped with a depressed stilling basin. This devise is still in use in several combined sewer systems and may have unfavourable consequences on the water quality of the receiving bodies. The present paper is part of a study to economically modify the existing structure in order to prevent dry weather sedimentation and heavily polluted first flush flow. The experimental free surface profiles observed in different conditions were compared with numerical simulations obtained using the computational flow dynamic software FLOW 3-D with the imposed conditions at the downstream boundary. The standard k- turbulence model is used in conjunction with the volume of fluid (VOF) free surface model. The computer simulations faithfully reproduce the water level in the upstream pipe branch and in the dissipation manhole. However, some discrepancies were observed between the measured and simulated jet, and in the position of the hydraulic jump.
Calenda, G., DI LAZZARO, M., Fiori, A., Prestininzi, P., Volpi, E. (2009). Channel drops: A comparison between CFD simulations and experimental observations. Standard design of hydraulic structures in urban drainage systems. In Standard design of hydraulic structures in urban drainage systems. Results of the MIUR-PRIN 2005 on the standardization of urban drainage manholes.