Round buoyant jet in shallow water: bed shear velocity

Abstract

SummaryThis paper examines the mixing processes that develop when a buoyant jet from a round outfall pipe enters a shallow moving body of water in a direction perpendicular to the current and focuses on the role played by the bed shear velocity developed in the receiving water. Different velocity profiles in the receiving water were produced using a triggering fence to modify the profile and hence the bed shear velocity. These changes simulated variations in the roughness of the bed. The results of an experimental study are presented where the effects related to the magnitude of the current, the bed shear velocity, and the locations of the free and bed boundaries on the jet mixing parameters are quantified. Findings are outlined which show that the dilutions of buoyant jets are significantly influenced by these parameters. Other mixing features are discussed including a “total cross sectional dilution” parameter and a novel width parameter. The role played by the Coanda Effect in influencing the mixing of the jet is addressed and mixing parameter results are compared with deep (unconlined) and shallow (confined) stationary results.