Abstract
Shock waves generated by underwater nanosecond pulsed discharge offer advantages such as high peak pressure, broad bandwidth, and strong controllability, showing promising application prospects in areas like underwater acoustic sources. Current research largely focuses on individual stages and lacks a full-process analysis framework that spans from discharge parameters to shock wave output. To address this, this paper develops a numerical simulation model covering both the pre-breakdown and main discharge stages. In the pre-breakdown stage, based on field-induced ionization theory, coupled equations of charged particle drift-diffusion, Poisson’s equation, and heat transfer are established to simulate the evolution of the streamer from initiation to bridging; the parameters obtained at the end of pre-breakdown are then used as initial values for the main discharge stage. In the main discharge stage, the plasma channel is modeled as a variable-resistance cylinder, and the discharge circuit is coupled with the energy conservation equation to quantitatively describe the conversion process from electrical energy to the mechanical energy of the shock wave, as well as to analyze the attenuation characteristics of the shock wave during near-field propagation. Based on the above, this paper systematically investigates the influence of pulse voltage amplitude, electrode gap, and electrode curvature radius on the discharge process and energy conversion. Increasing the voltage can shorten the breakdown time delay and enhance the deposited energy, but high-temperature radiation leads to a decrease in the shock wave energy conversion efficiency; increasing the electrode gap distance is beneficial for enhancing the deposited energy, but increases thermal radiation loss; increasing the curvature radius has a limited effect on improving energy conversion. The influence of each parameter on the shock wave amplitude exhibits a saturation effect, the intrinsic mechanism of which stems from the competition between the deposited energy gain and the dissipation mechanism. The integrated simulation framework established in this paper provides a basis for analysing parameter trends and for guiding the design of underwater pulsed discharge acoustic sources, subject to the assumptions and validation discussed in the paper.