Turbulent buoyant jets and plumes in flowing ambient environments have been studied theoretically and experimentally. The mechanics of turbulent buoyant jets and plumes in flowing ambients have been discussed. Dimensional analysis was employed to investigate the mean behaviour of the turbulent buoyant jets and plumes, such as the jet trajectories and the dilutions. The basic physical processes for a submerged turbulent buoyant jet released from sea outfall have been outlined and divided into four primary stages, namely, the zone of flow establishment, the stage of jet, the stage of intermediate and the stage of plume. The stability criteria for the upstream wedge created by the submerged
turbulent buoyant jet were established by applying the Bernoulli equations for a two-dimensional problem and by considering the front velocity driven by the buoyancy force for a three-dimensional problem. Comprehensive laboratory experiments were conducted to study the mean behaviour of turbulent buoyant jets and plumes in a flowing ambient by using both fresh and salt receiving waters. The experimental data on the jet trajectories and dilutions, for a horizontal jet in a coflowing ambient and for a vertical jet in a crossflowing environment, have been presented and successfully correlated using momentum and buoyancy fluxes and length scales. The analysis demonstrates that the experimental data on the jet trajectories and dilutions can be well correlated using the momentum or buoyancy fluxes and length scales, depending upon the types and regimes of the flows. The stability condition was verified using the experimental data and the flow regimes were categorized into three types regarding the formation of the upstream wedge, i.e. stable upstream wedge, unstable upstream wedge and no upstream wedge. In addition, the available field observated data on the initial dilutions for a horizontal jet issuing into a perpendicular crossflowing ambient have been presented and discussed. Mathematical modelling of the turbulent buoyant jets and plumes has been carried out by using both an integral model and a turbulence model. The integral model was developed on the basis of the volume control method ( for jets with two-dimensional trajectories ) and the differential method ( for jets with three-dimensional trajectories ). The turbulence model adopted here was the k - ε model based on Launder and Spalding. The mathematical models were used to predict the turbulent buoyant jets and plumes in flowing ambients. The predictions by the integral model and the turbulence model have been presented and compared with the available experimental data. The comparisons show good agreement between the model predictions and the laboratory measurements.