Laboratory study on inclined desalination discharges in perpendicular cross-flow

Abstract

To mitigate the ecological impact of dense effluents discharged from diffusers, understanding the influence of ambient currents and discharge characteristics on desalination outfall performance is crucial. For this purpose, a series of laser-induced fluorescence (LIF) experimental tests were conducted to address the combined effects of the flowing current strength and nozzle inclination in the discharge region for dense jets issuing into a plane perpendicular to the cross-flows. Various nozzle discharge angles (30°, 45°, and 60°) and cross-flow Froude numbers (urF=uau0×u0g0′D) are studied to assess 3D jet trajectory and concentration distribution. Empirical equations describing the dilution and geometrical characteristics of the jets are also derived. The findings indicate that deploying the 60° jet can achieve dilutions of over 50 % and 20 % compared to the 30° and 45° jets, respectively, due to its longer trajectory and greater expansion. Thus, the previously reported insensitivity of dilution to the nozzle angles in the range of 40°-70° for stationary ambient water is questioned herein when dealing with flowing currents. Moreover, the 60° jet is more sensitive to the changes in urF compared to the two other shallower angles. The presented outcomes provide valuable insights for safeguarding coastal water bodies through the efficient design of inclined dense outfall discharges.