Buoyant jets with three-dimensional trajectories

Abstract

Details of an experimental investigation into the behaviour of discharges with three-dimensional (3D) trajectories are presented. A light attenuation technique is employed to track the position of peak concentrations in the flow and the transition from weakly to strongly advected behaviour can be clearly observed: two peaks are evident at a given cross-section in the strongly advected region, whereas only a single peak occurs at cross-sections in the weakly advected region. Length scales, based on dominant momentum fluxes in the weakly and strongly advected regions, can be employed to locate the transitions between these distinctly different flow forms. Coefficients for these length scales have been determined based on numerous studies of discharges following an essentially 2D path. Length scale estimates, based on the 2D path coefficients, and the measured transition locations from the present study indicate that the transition to strongly advected behaviour can be delayed significantly, if the discharged fluid follows a 3D path. This delay has significant implications for the dilution rates of the effluent.

Keywords:

• Ambient currents
• buoyant jets
• experimentation
• light attenuation
• three-dimensional trajectories

Acknowledgements

The authors would like to thank Ian Sheppard and Kevin Wines for their invaluable technical support in tackling these challenging experiments.

Additional information

Notes on contributors

Mark J. Davidson

IAHR Member, [email protected]

Roger I. Nokes

IAHR Member, [email protected]