Novel Diversion Structure for Supercritical Flow

Abstract

In urban drainage systems, it is usually necessary to split the storm water discharge among different sewer branches because of limited flow capacity of either hydraulic structures or sewer lines. For this purpose, sewer sideweirs and leaping weirs are generally used as diversion overflow structures. For supercritical approach flow, the former is not recommended because of the occurrence of hydraulic jumps, whereas the latter requires an outlet located below the approach flow sewer bottom. To overcome these constraints, a novel compact hydraulic structure is proposed. It consists of a frontal rectangular intake, representing the diversion sewer inlet, located in the approach flow sewer and parallel to its bottom. A 6.67:1 scale model was tested over a range of hydraulic and geometrical parameters to determine its head-discharge relationship, developing a dimensionless equation relating the diversion discharge to the geometrical properties of the intake under supercritical flow conditions. The limited hydraulic structure size provides cost-effectiveness and ease of installation and maintenance.