Characteristic of cavitation bubbles and shock waves generated by pulsed electric discharges with different voltages

Abstract

In the cases that underwater pulsed electric discharges should be applied with high repetition rates, such as medical applications, characteristic of the generated cavitation bubble and shock waves should be considered. In our previous research, underwater shock waves focusing by pulsed discharges using a magnetic pulse compression unit (MPC) were studied. In this paper, effects of pulsed electric discharge parameters, like voltage amplitude and pulse duration, on the characteristic of cavitation bubbles and shock waves were visualized and analyzed. Pulsed discharge shock waves and cavitations were produced by using a MPC unit. The water was degassed by a vacuum pump in order to eliminate the influence of dissolved air. In order to prevent electrical discharge oscillation and to increase the electrode life time, degassed saline electrolyte was used. The whole sequences of shock wave generation by discharge plasma, bubble growth, bubble collapse, and secondary shock wave generation near the electrode were visualized by time-resolved high speed shadowgraph method. Using the visualization results and image analysis, radius and collapse time of cavitation bubbles and their shock waves pressures were evaluated.