Comparison study on underwater bubble dynamics via pulsed discharge and electrical explosion

Pulsed discharge in water is an indispensable method to carry out laboratory simulation of underwater explosion effects and bubble dynamics research, which has attracted more and more attention in recent years. In this paper, discharge characteristics and spatial-temporal evolution behavior of underwater bubbles in needle-needle pulsed discharge and electric explosion of a fine copper wire (
$50\ \mu\mathrm{m}$
in diameter) are compared in detail. High-speed photography and electrophysical diagnostics are applied to characterize dynamic processes. The results indicate that under the condition of 4 J stored energy, the deposition energy of underwater electrical wire explosion can reach 3.83 J (>95 %), which is 10 times higher than that of pulsed discharge under similar stored energy. The peak electric power of electrical wire explosion is 22.65 MW, which is two orders of magnitude higher than the pulsed discharge. Compared with the underwater pulsed discharge, the bubble diameter produced by the underwater electrical wire explosion is larger (the length of copper wire is 1 cm, the maximum diameter of the bubble is 2.64 cm), the expansion rate is faster, and the duration is longer. The bubble morphology generated by underwater pulsed discharge is irregular and influenced by the randomly-developed streamers, whereas the bubble generated by underwater electrical wire explosion exhibits obvious shock wave, explicit gas-liquid boundary, and typical cylindrical-spherical evolution process, close to the case of underwater explosion. In addition, for copper wire electric explosion, the larger the stored energy, the larger the bubble radius and the longer the duration.