Mixing of a Rosette Jet Group in a Crossflow

Abstract

Partially treated wastewater is often discharged into coastal waters through an outfall diffuser fitted with clustered ports on risers. On each riser the effluent is discharged through two to eight ports arranged circumferentially, in the form of a rosette-shaped buoyant jet group. The near field mixing of such a jet group in a tidal flow is determined by the merging and interaction of coflowing, oblique-flowing, cross-flowing, and counterflowing jets. Despite numerous studies, a general predictive method for such complex jet groups has not been reported; ocean outfall design is often based on comprehensive physical model experiments. The mixing of merging nonbuoyant and buoyant jets issuing from a rosette outfall riser into an ambient current is studied experimentally by using the laser-induced fluorescence technique. Detailed cross-sectional measurements of the scalar concentration field downstream of the bent-over jets are made. The trajectories of multiple and individual jets discharging at various an...