Numerical study on dilution of an oscillating jet in current environments

The mixing behavior of an oscillating jet under the influence of currents remains incomprehensive. This study uses a three-dimensional large eddy simulation model to investigate the phase-averaged and time-averaged concentration distribution of three-dimensional scalar structures in the oscillating jet under a current environment. The effects of dimensionless parameters on dilution characteristics are also analyzed. The results indicate that increasing the jet-current velocity ratio (Rjc) and the amplitude-jet velocity ratio (Raj), while decreasing the Strouhal number (St), can enhance the dilution capacity of the receiving water. To quantify the oscillatory effect of jets on the initial dilution of wastewater discharge, semiempirical equations for the cross-sectional minimum dilution (Sc) and the visual area (A25%) of the oscillating jet in a current environment are developed using the least squares method. The oscillatory nature of the jets is found to behave similarly to wave effects. Furthermore, the empirical equations for the initial dilution of oscillating jets in current environments are structurally consistent with those for non-oscillating jets in wave-current coexisting environments. This study highlights the positive impact of oscillating jets on mixing and dilution.