Mixing of 30° and 45° Inclined Dense Jets in Shallow Coastal Waters

This study experimentally investigates the effect of shallow water depth on the mixing of 30° and 45° inclined dense jets. Three different mixing regimes were identified, namely, the full submergence, plume contact, and centerline impingement regimes. The mixing characteristics in these three regimes, including the jet trajectory and minimum dilution at the water surface ($S_S$) as well as at the return point near the seabed ($S_r$), were quantified with respect to the densimetric Froude number ($\mathsf{F}$) and cover water depth ($H$). The nondimensional cover water depth, $H/D$, was found to be a suitable normalization parameter for shallow water scenarios. The transitional $\mathsf{F}·D/H$ among the regimes, the asymptotic limits of the minimum surface dilution at large $\mathsf{F}$, and the various linear coefficients were also determined. Overall, it was found that the surface constraint in the plume contact and centerline impingement regimes, lengthens the jet-spreading distances and reduces the surface dilution, while the bottom dilution remains relatively constant. The results enable the assessment of the mixing characteristics of the inclined dense jet in shallow coastal waters with possible surface contact for environmental impact assessment.