This paper reports the results of experiments on underwater shock wave propagation and reflection at the interface of certain materials conducted to improve the understanding of shock wave interaction with the interface of materials with different acoustic impedance. An underwater shock wave was generated by detonating a micro-explosive (AgN3) near the interface of materials with different acoustic impedance (water and acrylic/aluminum/stainless steel/air). The process of shock wave propagation was visualized by the shadowgraph method and recorded by an ultra-high-speed camera. The pressure history near the interface was measured simultaneously by a needle hydrophone with high spatiotemporal resolution. Time-resolved shadowgraph images show that a compression wave was reflected from a thin interface plate, and an expansion wave, which propagated downward, was then generated in water by reflection from the air. In addition, a cavitation bubble was created behind the expansion wave. The simultaneously measured pressure history also shows that an expansion wave propagated behind the compression wave.
shock wave, expansion wave, micro-explosive, acoustic impedance, shadowgraph, pressure history