Experimental investigation of air entrainment by vertical plunging liquid jet

This paper presents experimental results and predictive model on the air entrainment flow rate due to the vertical plunging liquid jet. Three types of fluids with different physical properties were utilized as a working fluid for the experiment. Air entrainment flow rate was measured using soap meniscus method and various geometrical parameters including nozzle diameter (13-16 mm), fall height (105-210 mm), pool depth (30-180 mm), and angle of the bottom pool surface (0-75°) were changed to investigate the effects on air entrainment rate. Plunging tube was installed around the falling jet and impinging point. For the current experimental conditions, it was found that the air entrainment rate depends on the product of Weber number and Laplace length scale, and new predictive model on air entrainment ratio, defined as the entrained air flow rate divided by impinging jet flow rate, is proposed. The proposed model is capable of predicting air entrainment ratio at a mean absolute relative deviation of 15.9% at the given experimental conditions.