NUMERICAL INVESTIGATION OF TANDEM BUOYANT JETS UNDER REGULAR WAVES USING A VOF APPROACH

Underwater sewage systems release a lot of water into the environment, which may alter the properties of the water and have an impact on marine ecosystems. This study numerically investigates the hydrodynamic behavior of tandem buoyant jets discharged under regular wave conditions typical of shallow coastal outfalls. Six scenarios combining jet speeds of 0.7-1.06 m/s, wave periods of 1-2 s, and wave heights of 0.02-0.04 m were simulated (Cases 1-6) using a two-phase volume of fluid (VOF) model. The free-surface elevation generated by the computational model matches published experimental data with < 5% deviation, confirming the robustness of the approach. Results show that 1 s waves intensify oscillatory forcing, increasing vertical velocity fluctuations by 35-40%, relative to 2 s waves due to more rapid crest-trough cycling. Increasing wave height from 0.02 m to 0.04 m enhances vertical displacement amplitudes by 20-25%, producing stronger disruption of the jet core. Higher jet velocity (1.06 m/s) increases the centerline vertical momentum by 30-35%, reducing the influence of wave-induced shear. Far-field vertical velocity decreases by more than 50% relative to the jet centerline under all wave conditions due to dominant wave-induced orbital motion. The findings provide new quantitative insight into jet-wave interactions, contributing to improved outfall design in wave-dominated nearshore environments.