عنوان مقاله [English]
نویسندگان [English]چکیده [English]
In the present article, effective parameters of the buoyant jets have been evaluated in the stagnant ambient fluid. The jet parameters, geometry parameters and environmental parameters are investigated. Using dimensional analysis, a set of dimensionless functions was obtained. To achieve the exact functions, a physical model was built in the hydraulic laboratory of Shahid Chamran University, Iran (SCU). 215 experiments were set on base of different jet diameter, different concentration of jet injection and different convergence angle of jets. To precede the goals of the present study, the positive mixing length and trajectory characteristics from a buoyant jet and the maximum length of upper and inferior limits of trajectory have been considered. The velocity profiles of adjacent sections near and far field of location jet injection was measured using profiler acoustic, UVDP. The velocity profiles were compared with the theoretical normal Gaussian distribution. Finding shows that the gathered data in this field have been satisfactory correlated. In addition the concentration and dilution in the different sections along the jet flow were measured. Findings show there are satisfactory correlation between experimental data and theoretical formula. The lengths of falling jet trajectory were analyzed as the ratio of trajectory length to port diameter (x/dp) versus relative trajectory elevation ((Z0-Zu)/x). According to the results, increasing on concentration of jet flow causing a density gradient between jets and receiving fluid and change in the buoyancy forces involved, has major influence on the lengths of falling trajectory. Findings show there is a nonlinear correlation between the trajectory characteristics and jet flow properties. As change of contraction angle, from 15 to 90 degrees, upper limit of trajectory increased to 25 percents. While contraction angle increase from 15 to 90 degrees, the inferior limit increase to 28 percents.
Key words: Buoyant jet, Contraction angle, Trajectory, Flow pattern, Spreading Coefficient