水下等离子体声源的冲击波负压特性

Shock wave negative pressure characteristics of underwater plasma sound source

基于修正的Rayleigh气泡脉动方程对水下等离子体声源放电产生的强声冲击波的传播过程进行了分析;利用Euler方程作为控制方程组,建立了水下等离子体声源的聚束声场模型,通过仿真计算获得的传播云图对冲击波负压的形成机理进行了直观的理论分析.结果表明:经过聚能反射罩反射汇聚得到的聚束波在反射稀疏波和水的惯性作用下,聚束波周围水域产生了拉伸,形成负压区,如果拉伸力大于水的抗拉上限,就会使得水中形成不连续现象,即出现空化气泡;此外聚能罩边缘处产生的衍射波进一步加剧了负压的产生,边缘衍射波最终与拉伸波叠加,使冲击波负压达到最大值;通过对比仿真波形和实验波形,从而验证和进一步揭示了冲击波负压的形成原因.研究结果对认识水下冲击波的传播规律和进一步改进等离子体声源的设计具有指导意义.

The propagation process of intense acoustic shock wave, generated by the discharge of underwater plasma sound source, is analyzed based on a modified Rayleigh model. The bunching sound field model of underwater plasma sound source is established by using the Euler equation as the control equations. The formation mechanism of the shock wave negative pressure is analyzed theoretically and intuitively through the sound field charts obtained by simulation. The results demonstrate that the water around the bunching wave will be stretched and form a zone of negative pressure with the combination of the rarefaction wave and the inertia of water. It will make the water form a discontinuous phenomenon if the stretching force is greater than the ultimate tensile strength of the water, the phenomenon of cavitation bubble will appear at this time. Besides that, negative pressure will be aggravated by the diffracted wave generated at the edge of the energy-gathered reflector, and the shock wave negative pressure will reach a maximum value by the superimposition of the edge diffraction wave and the stretch wave. The reasons for the formation of the shock wave negative pressure is testified and revealed further by comparing the waveforms of simulation and experiment. The study results provide a theoretical guide for understanding the propagation law of underwater shock wave and further improving the design of the underwater plasma sound source.