Underwater shock wave induced by pulsed discharge on water

Plasmas on liquids have provided significant applications in material, environmental, and biological sciences. The mechanisms of these chemical reactions in liquids have been primarily discussed by the plasma–liquid interactions and convection by an electrohydrodynamic flow. Although shock waves play a significant role in the radical formation, agitation, and cell destruction, not much information is available on underwater shock waves induced by the surface discharge on water. In this study, an underwater shock wave generated by the pulsed surface discharge on water using the laser shadowgraph method has been demonstrated. The results reveal that the shock wave generated by the discharge on water was transmitted into the water. The mean velocity of the shock wave reached 1.7 km/s. The results indicate that the surface discharge accelerates the reaction in the water by the combined action of the underwater shock wave and the plasma reaction at the air–water interface. The results are expected to aid in the understanding the mechanisms of existing applications, such as decomposition, synthesis, and sterilization.

Early Dynamics of a Laser-induced Underwater Shock Wave

The objective of this paper is to observe and investigate the early evolution of the shock wave, induced by a nanosecond pulsed laser in still water. A numerical method is performed to calculate the propagation of the shock wave within 1µs, after optical breakdown, based on the Gilmore model and the Kirkwood-Bethe hypothesis. The input parameters of the numerical method include the laser pulse duration, the size of the plasma and the maximally extended cavitation bubble, which are measured utilizing a high time-resolved shadowgraph system. The calculation results are verified by shock wave observation experiments at the cavitation bubble expansion stage. The relative errors of the radiuses and the velocity of the shock wave front, reach the maximum value of 45% at 5 ns after breakdown and decrease to less than 20% within 20 ns. The high attenuation characteristics of the shock wave after the optical breakdown, are predicted by the numerical method. The quick time and space evolution of the shock wave are carefully analyzed. The normalized shock wave width is found to be independent of the laser energy and duration, and the energy partitions ratio is around 2.0 using the nanosecond pulsed laser.

Evaluation of anti-explosion performance of Shuibuya concrete-faced rockfill dam slabs subjected to strong shock waves caused by an underwater explosion

A concrete plastic-damage model, the extended Drucker–Prager model for rockfill, and acoustic elements for water were introduced and applied to the impact fracture analysis of a concrete-faced rockfill dam–water three-dimensional system. The plastic-damage dynamic analysis process was used in combination with the concrete compressive and tensile damage model. The 223-m high Shuibuya concrete-faced rockfill dam was analyzed using an explicit integration. Numerical simulations of the damage threshold, rockfill modeling, and interface processing were conducted to research the effect of the anti-explosion performance that occurs when a concrete slab is subjected to an underwater shock wave. The simulation results indicate that the main regions of weakness in the slabs during an underwater shock wave are determined by the tensile damage. The slab’s anti-knock weak areas appear in the right dam abutment and the top of the left dam. The anti-knock performance in the upper slab is inferior to that of the lower slab. Specific local optimization steps should be applied at these locations to improve the slabs’ anti-knock capabilities, which are important for designing concrete-faced rockfill dams.