Radially spreading surface flow

When discharged in shallow water a vertical buoyant jet will experience relatively limited dilution before it surfaces. In this case, dilution occurring in the radially spreading surface layer emanating from the vertical jet will become of importance if regulatory requirements for mixing are to be achieved. The present study was undertaken to identify the details of the structure of the radially spreading surface layer associated with the discharge of a vertical buoyant jet in shallow water. Flow visualization was used to examine the surface flow for a variety of initial jet conditions. Large scale vortex structures propagating outward from the region of surface impingement were observed to occupy the full extent of the surface flow. Significant entrainment into the radial flow occurred as a result of these structures. The radial surface flow was found to be highly intermittent and discontinuous in nature, a well defined interface between the outward flowing upper layer and inward flowing lower layer did not exist at any given time. No internal hydraulic jumps were observed.