Validity of the sonar equation and Babinet’s principle for object scattering in a shallow water waveguide
Validity of the sonar equation and Babinet’s principle for object scattering in a shallow water waveguide
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DOI：
10.1121/1.427393
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发表时间：
1999-08
影响因子：
2.4
通讯作者：
N. Makris;P. Ratilal;Yisan Lai
中科院分区：
文献类型：
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作者：
N. Makris;P. Ratilal;Yisan Lai
最近的研究表明，声纳方程可以为浸没在海洋波导中的非紧致（ka>1）球体的非前向散射提供合理的近似。球体在非前向的全向散射特性使得球体的远场平面波散射函数能够像在自由空间中一样在单散射波导解决方案中被考虑在内。然而，球体在前向散射的高度方向性阻止了这种分解，并导致前向声纳方程预测的显着偏离。根据巴比内原理，自由空间中入射平面波作用下的非紧球体的前向散射场几乎与相同投影面积的圆盘的前向散射场相同。因此，表明声纳方程可以显着高估从浸没在海洋波导中的直立板或盘散射的场。这些扁平物体产生了有限物体可能产生的一些最具方向性的散射。研究还表明，在海洋波导中，直立的圆盘和具有相同大圆面积的同等位置的球体可以具有几乎相同的前向散射场，就像在自由空间中一样。
It has recently been shown that the sonar equation can provide a reasonable approximation to nonforward scattering from a noncompact (ka>1) sphere submerged in an ocean waveguide. The omnidirectional scattering characteristics of the sphere in nonforward directions enables the sphere’s far‐field plane wave scattering function to be factored in the single‐scatter waveguide solution just as it is in free space. The highly directional nature of the sphere’s scattering in the forward direction, however, prevents this factorization and leads to significant departures from sonar equation predictions in the forward direction. By Babinet’s principle, the forward scattered field from a noncompact sphere subject to an incident plane wave in free space will be nearly the same as that of a disk of the same projected area. Accordingly, it is shown that the sonar equation can significantly overestimate the field scattered from an upright plate or disk submerged in an ocean waveguide. These flat objects yield some of the most directional scattering possible from a finite body. It is also shown that in an ocean waveguide the upright disk and an equivalently located sphere with the same great circle area can have nearly identical forward scattered fields, just as in free space.