Mechanism of unsteady spray formations by shock wave and bubble formation induced by breakdown

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An atomization process of water injected by a laser breakdown and an electrical spark discharge was investigated experimentally. Bubbles were formed by the laser irradiation with a convex lens and the electrical spark discharge in a vessel with optical windows, and the behavior of shock waves, bubble formations, bubble growths and collapses were observed using a high speed video camera. Water was injected from a nozzle. In the case of the laser breakdown, bubbles were formed along the laser path mainly at the upstream of the beam west. Bubble interactions were clearly observed, which affect the maximum radius and the bubble life time. Liquid thread injections were observed right after the laser breakdown. After a delay time of approximately 0.4 ms, a strong water jet was injected from the nozzle. In the case of the electrical discharge, bubble formations and water injections were also recognized although the injection was much weaker compared with that by the laser breakdown.