Scattering of sound by a target can be described as a wave radiated by virtual point sources inside the target. In the Rayleigh scattering regime, the strength of the virtual sources can be calculated analytically. When a target is located close to the ocean surface or another reflecting boundary, reflections of the incident and single-scattered waves from the boundary lead to multiple scattering from the target, with the target being insonified by nearby virtual sources. At low frequencies and for shallow targets, the distance from a virtual source to the target is not necessarily large compared to the acoustic wavelength or the target’s dimensions. Then, multiple orders of scattering make significant contributions and incident wave fields that cannot be approximated as a plane wave. This paper takes advantage of the virtual source concept and recently derived explicit analytic representations of 2D acoustic Green’s functions in unbounded fluids with inclusions of a circular cross-section, to develop a simple, intuitive, and numerically efficient model of multiple scattering. Scattering from soft, hard, and fluid targets is considered. The model is used to study the acoustic field in the vicinity of cylindrical targets near a pressure release surface or a hard bottom.

中文翻译：

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位于边界附近的无限圆柱体对低频声散射的半解析数值效率模型

目标对声音的散射可以描述为目标内部虚拟点源辐射的波。在瑞利散射状态下，虚拟源的强度可以解析计算。当目标靠近海洋表面或另一个反射边界时，来自边界的入射波和单散射波的反射导致目标的多次散射，目标被附近的虚拟源声波穿透。在低频和浅目标时，与声波波长或目标尺寸相比，虚拟源到目标的距离不一定很大。然后，多级散射做出重大贡献，入射波场不能近似为平面波。本文利用虚拟源概念和最近推导出的二维声学格林函数在具有圆形横截面的无界流体中的显式解析表示，开发了一个简单、直观且数值有效的多重散射模型。考虑了来自软、硬和流体目标的散射。该模型用于研究靠近压力释放表面或硬底的圆柱形目标附近的声场。