Laboratory Study on Dense Discharge through Rosette Diffusers with Multiple Nozzles

Laboratory experiments on dense discharge from rosette-type diffuser typical of brine disposal from seawater desalinations are reported. Single risers with 1, 2, 4, and 6 nozzles pointing upward at 60° are investigated. Tracer concentration fields on the jet’s central plane were measured using planar laser-induced fluorescence (PLIF) from the nozzle tip to the point of bottom impingement. Centerline trajectories, maximum and terminal rise heights, impact point location, and impact point dilution are reported. Flow characteristics for one and two-port risers were found to be similar; however, increasing the number of ports beyond two reduces flow trajectory and dilutions. Compared to a single-port riser, the four-port rosette riser achieves an average dilution reduction of 16% at impact point, while the six-port riser reduces dilution even more, by approximately 28%. Jet merging prevents intrusion into the region between the descending jets and consequently modifies the flow field, thereby influencing the design of multirosette diffusers.