摘要
为研究水下低频声波的散射机理,推导出了低频球面声波近场与远场散射声压的统一渐近解。首先,给出了低频球面声波遇到软、刚性阻抗等球形障碍物散射声压的无穷级数解;结合低频、近场和远场的假设条件,合理选取无穷级数解中球Bessel函数、球Hankel函数的近似形式,分别推导出了近场和远场散射声压的渐近解;在声源距散射体较近的假设条件下,推导出了近场和远场散射声压的统一渐近解。以此为基础,研究了低频球面声波的近场和远场散射特性,研究表明:低频球面声波的散射声压可以表示为单极子声源和偶极子源的叠加,推导出的统一渐近解与经典解在低频条件下能够保持一致;声源距障碍物较近、接收点距声源或障碍物较远时,软球体的回声强度为圆形,而刚性球体和阻抗球的回声强度为葫芦形;声源距障碍物较远、接收点距声源较近时,回声强度与其形状有关。研究结果可为水下目标的低频探测、低频声波散射的控制提供理论参考。
To investigate the scattering mechanism of underwater low-frequency acoustic waves,a uniform asymptotic solution of near-and far-field acoustic pressures is derived.First,the infinite series solution of the scattering acoustic pressure for low-frequency spherical acoustic waves encountering spherical obstacles such as soft and hard impedance is provided.Based on the assumptions of low frequency,near-and far-field,the approximate forms of the Bessel and Hankel functions are employed to derive the asymptotic solution.By assuming that the acoustic source is near the scatter,a uniform asymptotic solution of the near-and far-field scattering acoustic pressures is derived.Subsequently,the nearand far-field scattering characteristics of a spherical acoustic wave are investigated.The results show that the low-frequency scattering acoustic pressure can be expressed as a superposition of fields because of a monopole source and dipole sources,the uniform asymptotic solution derived is consistent with the classical solution at low frequency.When the source is near the obstacle and the receiver is far from the source or obstacle,the echo strength of the soft sphere is shaped like a circle,whereas those of the hard and impedance spheres are shaped as“gourds”.When the source is far from the obstacle and the receiver is near the source,the echo strengths are related to the shape of the incident wave.The results are useful for controlling acoustic scattering and detecting low-frequency waves of underwater targets.
作者
张健
周奇郑
王德石
ZHANG Jian;ZHOU Qi-zheng;WANG De-shi(College of Weaponry Engineering,Naval University of Engineering,Wuhan 430033,China)
出处
《水下无人系统学报》
北大核心
2020年第5期487-495,共9页
Journal of Unmanned Undersea Systems
基金
国家自然科学基金(11602300).
关键词
水下目标
低频声波
球形障碍
渐近解
散射特性
underwater target
low-frequency acoustic wave
spherical obstacle
asymptotic solution
scattering characteristic
