Diffusion of a Surface Marine Sewage Effluent

Abstract

Any scalar concentration discharging to the sea through a freshwater release is a thermodynamic two-phase flow including different densities and different temperatures. Because of Reynolds similarity, physical models are not feasible to use and numerical models such as CFD-RANS are the solutions. A series of numerical experiments have been conducted to derive an empirical formula that determines the length of the 95% scalar concentration reduction, useful for primary and emergency engineering-environmental decisions. Results show that the scalar concentration intrusion length is a function of seawater density-temperature, freshwater density-temperature, sea current Froude number, effluent jet Froude number, and the scalar concentration in which among those, the sea current Froude number has the most effective role in which as an example of the lowest and highest tested sea current velocities, an effluent discharge of 0.052 m3/s with a concentration of 1 Kg/m3 and effluent jet velocity 0.245 m/s in 3.2 meters from the effluent source reaches to the 95% scalar concentration reduction when there is a high-velocity sea current (0.5 m/s) while in the presence of a low-velocity sea current (0.05 m/s), the same effluent discharge with the same scalar concentration and the same effluent jet velocity, the length of the 95% scalar concentration reduction increase to 42.8 meters from the effluent source.