Experimental results on inclined turbulent round jets with negative buoyancy discharging in a calm homogeneous fluid are presented. Six different discharge angles from 45° to 90° to the horizontal are studied, and the jet evolution is recorded by means of a video camera. Results concern the main geometrical characteristics of the jet trajectory, i.e. the initial terminal height of rise reached by the jet at flow initiation, the final terminal height of rise observed at steady state, the horizontal distance from the source at which the terminal height is observed and the horizontal distance to the point where the jet returns at the source elevation. The densimetric Froude number at the source ranges between 7 and 60, whereas the Reynolds number is generally higher than 6000. Results are given in dimensionless form and confirm theoretical considerations obtained by dimensional analysis.

Experiments on concentration measurements in round turbulent negatively buoyant jets discharging into a calm homogeneous fluid at three different angles are presented. Detailed measurements using a micro-scale conductivity probe were carried out at the horizontal location of the terminal rise height, mostly along the vertical of the axial jet plane and in the transverse direction. The dimensionless vertical distribution of the mean concentration is found to be asymmetric, whereas the transverse distribution is approximately Gaussian. At the same horizontal location, the vertical distribution of the concentration turbulent intensity has a maximum at a point systematically higher than the jet axis. The width of the mean concentration distribution, the heights to the location of the maximum mean concentration and to the maximum turbulent intensity as well as the minimum dilution are determined. From measurements in the region where the jet returns to the source elevation, the minimum dilution and the horizontal distance to the return point are estimated.

Desalination plants commonly discharge large quantities of brine wastes into the adjacent coastal waters causing potentially harmful environmental impacts. To increase the effluent dilution prior to impingement on the sea floor, disposal by means of upwards inclined dense (negatively buoyant) jets can be applied. This paper presents an overview of experimental results on inclined negatively buoyant jets, focusing on the impact dilution achieved and illustrating its dependence on the jet inclination and the source characteristics, expressed by the densimetric Froude number F_o. It is shown that, in a stagnant ambient, the impact dilution for a certain discharge angle is well linearly correlated to F_o (for F_o, larger than about 20) and increases with the angle but is not very sensitive to it in the practical range between 30° and 75°. Typical dilutions attained are of the order of 50. The effect of ambient flow is also briefly discussed.

A 3-D CFD model based on the Volume of Fluid method to calculate the free surface was used to study supercritical flow in gradual open channel expansions. The model was first applied to a modified Rouse expansion, for which extensive experimental data are available. A detailed comparison between the numerical and the experimental results concerning surface profiles, velocities, free surface uniformity, and shock front location showed satisfactory agreement, especially for lower supercritical Froude numbers. The model was subsequently applied to optimize and finalize the design of a compound expansion structure with variable bottom elevation, piers, and inner walls. CFD calculations showed that flow conditions in this structure are satisfactory, provided that bottom ramps are used to ensure a uniform variation of the bottom elevation

An analytical approximation to the entire centerline trajectory of inclined round dense jets in dimensionless form is proposed, in terms of a fourth degree polynomial. The coefficients of the polynomial for a certain inclination angle can be easily obtained if the position of the maximum height and the return point are known. Experimental data of the authors are used to determine these coefficients for six inclination angles between 35° and 75°. The resulting trajectories are then compared to data of other investigators and found to be in good agreement. The variation of the polynomial coefficients with inclination angle is also studied. The proposed analytical expression allows for a straightforward computation of the trajectory length for any inclination angle in the range studied. It is found that the longest trajectory occurs for the 60° angle. The relation between the computed length and the measured minimum (centerline) dilutions at the location of maximum height and at the return point is examined. Finally, the laws governing the variation of the minimum dilution with the axial distance from the source are explored and similarities with the laws of simple jets and plumes are discussed.

Experimental measurements of concentrations were performed for vertical dense jets discharged downwards to a horizontal or a sloping bottom, aiming at: (a) determining the dilution at the impingement point on a solid bed and assess the influence of the boundary, and (b) evaluating the additional dilution achieved within the density current, which forms in the vicinity of the impingement point. It is found that the presence of the solid boundary affects the axial dilution of the approaching jet up to a distance of h_D, which is well correlated to the source height and the length scale L_M. The dilution at the impingement point on the boundary is reduced appreciably compared to that of a boundary-free jet at the same location. The additional dilution within the density current on a sloping bottom is well correlated to the dimensionless distance from the impingement point. Dimensionless empirical equations are proposed for the dilution at the impingement point and in the density current near the bed, in terms of geometrical parameters and the densimetric Froude number.