Investigation of brine jet behavior using computational fluid dynamics models

Marine outfall systems are often used for the safe disposal of brine, which is the byproduct of desalination plants, and brine is discharged into ambient sea and ocean waters. It is important to ensure a sufficient dilution to avoid the negative effects that brine might cause on marine ecosystems by changing the temperature, salinity, and density of the ambient water in an abrupt manner. For this, the hydraulic design of the diffuser is the most important task for the design of the entire outfall, and a proper design is only possible through a thorough analysis of brine jet geometry, behavior, and dilution efficiency. In this study, the effects of different diffuser designs under certain ambient and hydraulic design conditions on brine jet geometry, behavior, and dilution efficiency were investigated using three-dimensional Computational Fluid Dynamics (CFD) models. For this purpose, first a reference model was created and validated using experimental data from a previous study. Then, based on this model, different models were created and simulated. In each model, only one of the parameters, discharge angle, number of ports, port spacing, port diameter, and jet velocity was changed, and the rest was kept the same as in the previous model to investigate the effects of these differing parameters on brine jet characteristics, behavior, and dilution within the near-field region. Results reveal that discharge angle, port spacing, and jet velocity affect jets' geometries, behavior, mixing and and dilution processes within the near-field significantly.