Mixing of coflowing jets in rivers

Domestic and industrial wastewater effluents are often discharged into rivers after some treatment. An effective way of rapidly reducing effluent concentrations to acceptable levels within a mixing zone is to discharge the effluent in the form of multiple jets into a coflowing river flow at some distance from the riverbank. An accurate and efficient predictive model of multiple coflowing jets is required for impact and risk assessment of environmental discharges into rivers. In the present study, a new semi-analytical model for multiple coflowing jets is developed using the method of superposition based on Reichardt s hypothesis. Jet excess momentum fluxes are hypothesized to be Gaussian and additive, which is supported by both theory and experimental observations. The predicted jet mixing characteristics of multiple coflowing jets from the present model compares favorably with basic experimental data. The present model is able to predict the entire concentration field, and thus mixing zone, downstream of an effluent discharge, and has potential application in river discharges.