Experimental study on the effect of the sawtooth nozzle structure on bubble behaviors

Abstract

The initial formation of bubbles has a significant impact on bubble dynamics and acoustics. Meanwhile, the bubble initial shape is affected by the nozzle boundary. In this study, the processes of bubble generated from sawtooth nozzles have been investigated by means of controlled experiments. A three-dimensional visualization imaging system is used to study bubble behaviors. The morphology and the time-frequency spectrum of the sound pressure signal are analyzed synchronously. Moreover, the effects on bubble trajectory are also studied. Results show that sawtooth nozzle is not conducive to bubble detachment, resulting in larger bubble diameters than the circular nozzle. With the gas flow rate increasing, bubble diameter increases. When the gas flow rate reaches a certain critical value, the surface tension is not sufficient to support the continued development of bubble size. Due to effect of the sawtooth structure, bubbles tend to break in the necking stage, accompanying by small bubbles. The generation of accompanying bubbles lead to the irregular generation of nearby bubbles. This study aims to reveal the effect of sawtooth nozzle structure on the initial formation of bubbles, so as to predict the flow patterns and sound signal characteristics of the bubbles.