The Plasma-Containing Bubble Behavior Under Pulsed Discharge of Different Polarities

Bubbles generated by a pulsed discharge in water can emit extensive pulsed acoustic waves. The bubble behavior is quite important for the electroacoustic analysis. This paper presents the high-speed photographs of the plasma-containing bubble behavior under the pulsed discharges of different polarities, including a single negative bubble, single positive bubble, and bipolar bubbles. The single bubble results show that the electrobubble energy transition rate of the positive discharge is higher than that of the negative discharge. The positive bubble has longer oscillation period and lower fundamental frequency than the negative one. For the bipolar bubbles, interaction between the two bubbles influences their own behavior, irrespectively of how long the gap distance between the electrodes is, and decreases the electrobubble energy transition efficiency and the acoustic wave amplitude as well. It is also interesting that the negative bubble oscillates twice, although its energy is much lower than that of the positive bubble, and the time of the negative bubble collapse at the end of the second period almost coincides with that of the positive bubble. Finally, the positive bubble breaks into pieces and vanishes faster than the negative bubble.