The sound emission of underwater pulsed discharges stimulated by an air bubble and the dynamic behavior of the corresponding cavity after breakdown

For underwater pulsed discharges, injecting an air bubble between electrodes serves as an effective external stimulation method. The bubble can significantly influence electrical parameters, sound waves, and pulsating cavities during the arc discharge and subsequent stages. Investigating the influence and mechanisms of the bubble in a single discharge event is essential for the optimized control of underwater pulsed discharges. This study utilized the schlieren optical system to record the morphology and evolution of sound waves and pulsating cavities, while hydrophones measured sound-wave intensity. A computational model based on the energy balance equation and the Gilmore model was used to describe the dynamic evolution of pulsating cavities. The results indicate that the presence of the bubble significantly alters the morphology of sound waves and the pulsating cavity, inducing transient stratification within the pulsating cavity. Furthermore, it demonstrates notable advantages in enhancing sound-wave intensity, increasing internal energy of the pulsating cavity, and improving energy conversion efficiency. The bubble guides and distorts the discharge channel, and there is an optimal bubble position that significantly enhances sound-wave intensity. The dynamic characteristics of the pulsating cavity are influenced by energy parameters and external constraints, and these parameters primarily affect the initial stage of the cavity. This study has important theoretical implications for the efficient application of underwater pulsed discharges in practical production scenarios.