Characterizing two inclined circular water jets plunging into an aeration tank

In this study, experiments were conducted to explore some properties of the bubble plumes of two inclined circular plunging water jets on a water surface in a cubic aeration tank. A particle image velocimetry (PIV) system was used to measure the two-phase jet velocities in both the lateral and axial positions. Other parameters of interest, such as gas holdup (εG), penetration depths (zp, m) and the height and width of the two-phase mixture due to the air entrainment, were also monitored. The value of bubble mean diameter (db, m) under each operating condition was determined by using images captured by the PIV system. The results of the normalized axial velocity for the gas and water jets showed a good mixing effect in the aeration tank. The results obtained under different plunging angles (α) showed that as do increases, zp also increases. Furthermore, under the same do, zp at α = 75° was found to be higher than the ones obtained under other cases. The combination of two inclined jets yielded a higher zp compared to that yielded by one inclined jet. The value of εG was found to decrease as do increased for the same liquid flow rate.

► This study investigated the effect of two inclined circular plunging jets on air entrainment in an aeration tank.
► A PIV system was used to measure the two-phase jet velocities in both lateral and axial positions.
► The results of the normalized axial velocity for the gas and water jets showed a good mixing effect in the aeration tank.
► The results showed that as the nozzle diameter increased, the penetration depths also increased.
► The combination of two inclined jets yielded a higher penetration depths compared to that yielded by one inclined jet.