The use of PDA in measuring air entrainment in an aeration tank utilizing a circular plunging jet

Air entrainment in water bodies is an effective mechanism for producing a gas-liquid interface that has several applications such as minerals-processing flotation cells, wastewater treatment and riverine re-oxygenation weirs. This study explores the air entrainment resulted from a circular plunging jet using a laser Particle Dynamics Analyzer (PDA) system. Two experimental setups were used to study the bubble plumes' properties in a hexagonal tank. The first setup used one pipe with a 2.5 mm nozzle diameter while the second setup used a nozzle diameter of 5 mm. Two different water flow rates and jet lengths were used within each setup. The properties of interest in this study were bubble characteristics (number, diameter, and velocity) as well as plume penetration depth and width. Air entrainment flow rate was then determined using the obtained data under each condition. The measured bubble axial mean velocity was then evaluated and modelled as a function of the water depth, the nozzle diameter, and the jet outlet mean velocity.