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

实验研究了激光击穿和电火花放电对水的雾化过程。在有光学窗口的容器中，采用凸透镜激光照射和电火花放电形成气泡，并利用高速摄像机观察了激波、气泡形成、气泡生长和破裂的行为。水从喷嘴中注入。在激光击穿的情况下，沿激光路径形成的气泡主要在光束的上游向西。气泡的相互作用对气泡的最大半径和寿命有明显的影响。激光击穿后立即观察到液体螺纹注入。在大约0.4 ms的延迟时间后，一股强大的水射流从喷嘴注入。在放电的情况下，气泡形成和注水也被识别出来，尽管注入比激光击穿弱得多。

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.