Investigation of Plunging Jet Characteristics in Aeration to the Stagnant Water Reservoir

A flow jet is a narrow stream of liquid that exits through a small diameter nozzle with a high velocity. Today, the use of hydraulic jets is of importance in various fields of engineering and industry. In this research, the characteristics of plunging jet in aeration into a stagnant water reservoir was investigated. For this purpose, first a physical model of reservoir was made and a circular nozzle was used to create a plunging jet. The experiments were performed for two discharges (Q) of 0.036 and 0.067 L/s, six vertical distances between the nozzle and the water surface (Lj) from 2 to 12 cm, six jet angles (θ) from 15o to 90o, and five densities of reservoir fluid (C) from 0 to 200gr/L. High-speed imaging technique was employed to investigate the characteristics of plunging jet. The results showed that for Lj=2cm and θ=90o, by increasing the Q from 0.036 to 0.067L/s, the hp increased by 13.3 %. Also, with increasing the Lj from 2 to 12 cm, at Q=0.067L/s and θ=90o, the hp increased by 10.4%. In addition, the results showed that at Lj=2 cm, Q=0.067 L/s, and θ=90o, by increasing the density of stagnant fluid from 0 to 200 gr/L, the hp decreased by 4.1%. For the experiments of this study, the highest penetration depth was observed at Q=0.067L/s, θ=90°, Lj=2cm at the density of C=0, which can be used as a recommendation in the aeration of sewage treatment plants, and at the oxygenation to the aquaculture ponds.