An experimental study on the characteristics of ejector-generated bubble swarms

Abstract: In this study, we report an experimental investigation into the bubble generation characteristics of a venturi-type ejector. A 5-mm-diameter vertically upwards nozzle placed in a 1-m ³ water tank was used to generate bubbles at between 2 and 20 L/min airflow rate corresponding to a Reynolds number range of 1.7–17 × 10 ³ . High-speed photography and image analysis were used for bubble visualisation and feature extraction. An image processing algorithm was used to obtain bubble velocity profiles and size distribution. It was established that when the nozzle was placed at the ejector’s neck, high bubble velocities result, especially at large Reynolds numbers. Bubble size distributions were created, and size variability is strongly correlated with the gas Reynolds number as well as other liquid properties describing gas flow encountering a quiescent bulk liquid. Graphical Abstract: [Figure not available: see fulltext.].