Electrical explosion across gas-liquid interface: Aerosol breakdown, shock waves, and cavity dynamics

The electrical explosion of a conductor driven by a pulsed current can be used to simulate the effects of explosions in the laboratory, including the resulting shock waves and bubble dynamics. A fine metallic wire can also be used to initiate pulsed discharge in different media. This study shows images of an exploding wire across an air-water interface for the first time in the literature. The transient process was analyzed using high-speed backlit photography as well as waveforms of the spectrum and discharge. Streamer-like discharge developed from a triple-junction point within the current pause to induce a restrike in metallic aerosol, verifying that gas discharge was prevalent in the system. An upward dense plasma jet accompanied by a crown-like water spike was then observed and led to violent plasma-water interactions (mushroom cloud-like cluster) that were examined through a hydrodynamic simulation. The Stark broadening of the H-alpha line at 656.28nm suggested that the electron density of the reaction zone could be 10(18)cm(-3) or higher. The resolved spatial-temporal images revealed that the plasma evolution process (in mu s) was much faster than hydrodynamic processes, including damage to the interface and perturbations of the bubbles (in ms). Water, thus, remained in a "rigid" state during the pulsed discharge, and the explosion of the wire in it was not an adiabatic process at a timescale of 10(2)mu s. Recombination and heat loss through the electrode governed the evolution of the post-discharge plasma, and the microscopic images revealed nano-lamellate nucleation on the surface of the electrode.