Validation of CORMIX model in simulation of single port brine discharge into seawater

Over recent decades, utilizing desalination plants with reverse osmose technology has been expanded all around the world whereas discharging their brine has become a serious environmental concern since this phenomenon can have catastrophic environmental consequences. Consequently, numerical models have grown which enable engineers to simulate and predict brine discharge before erecting marine outfalls. CORMIX is a functional and useful model which is able not only predicts discharge effluent behavior but also applies environmental limitation in its simulation. Therefore a plethora of researchers have used the CORMIX to design marine outfall and recognize jet's behavior in waterbodies. However, evaluating the reliability and accuracy of the CORMIX is crucial.

After conducting approximately 180 simulations, the CORMIX outcome for dilution at the impact point (Si), the horizontal location of the impact point (Xi), the horizontal location of the centerline peak (Xm), and the vertical location of the centerline peak (Zm) were normalized in dimensionless form.3.1. Validation of dense jet discharge into stagnant ambientAs for Si and Xi parameters, the more port diameter and discharge velocity decline, the more dilution rate at the impact point increase until the relation Fr>15 applied on CORMIX Results. After that, the outcome followed the experimental data trend with 0.2 and 0.025 differences for Si and Xi, respectively, meanwhile, they were underestimated which is so vital to be considered when the brine is discharged in a water body with a sensitive ecosystem. In addition, the Si parameter was more sensitive to discharge velocity fluctuation whereas Xi was not so reliant on port diameter and discharge velocity. However, Zm, which is an effective parameter for brine discharge in shallow water, was sensitive to both port diameter and discharge velocity also its results were accurate and reliable only if Fr>30. About Xm, the outcome of CORMIX for Fr>25 with grate turbulence followed experimental data while they were underestimated with 0.14 error.3.2. Validation of dense jet discharge into dynamic ambientIn dynamic ambient, due to lack of studies in terms of jet geometric features for θ =60° and σ =0, the study limited to dilution at the impact point. For Si, overall, decreasing port diameter and discharge velocity had a positive effect on the dilution rate increase. Although their changes were negligible when ur.Fr <0.2. Also, CORMIX results were overestimated with 0.77 compared to experimental data.

According to this study, in a stagnant ambient, port diameter and discharge velocity were capsulated in densimetric Froude number. Therefore, the results of CORMIX will be reliable only if the values of Fr has located in the specified domain (for Si and Xi, Fr>15 and for Xm and Zm, Fr >30). In dynamic ambient, besides port diameter and discharge velocity, the ambient velocity has an effective impact on dilution rate and jet geometric properties. Consequently, the design should be done based on relation ur.Fr >0.2 for Si parameter. Nevertheless, since CORMIX results were underestimated compared to experimental studies, calculated errors must be considered.