物理学报2019，Vol.68Issue(4)：230-238,9.DOI:10.7498/aps.68.20181475
浅海小掠射角的海底界面声反向散射模型的简化
Simplification of roughness bottom backscattering model at small grazing angle in shallow-water
摘要
Abstract
Bottom backscattering due to roughness seafloor is the main source of shallow water reverberation, especially in the waveguide with downward reflection profile or a calm sea-surface. Empirical backscattering models with a simple form has an important limitation to analyzing other characteristics of reverberation except for the intensity characteristics, which originates from optics and describes the relationship between the bottom backscattering strength and scattering grazing angle of plane-wave in half-infinite space. In the shallow water, such a plane-wave backscattering model cannot be used due to frequency dispersion. The model of bottom backscattering based on physical scattering principle is made to relieve such a limitation, but thereby bringing about another restraint by a geoacoustics model. The bottom backscattering model, which is formulated during modeling the full-wave reverberation theory at small grazing angle in range-independent shallow water waveguide, is simplified by combining with bottom reflection coefficient model which is independent of the geoacoustics model. The bottom reflection coefficient model as referred to the proposed phase parameter P in this paper is equivalent to velocity and density of sediment to describe sound field interacted with sea-bottom. Therefore simplification of bottom backscattering model can be handled by the phase parameter without any knowledge of bottom geoacoustic parameters. The angular dependency and intensity dependency of bottom backscattering due to roughness seafloor at small grazing angle are studied more in depth through such a simplified model. Marking 2/P as the cut-off point, the grazing angle is divided into two stages. Near the critical angle, as grazing angle is greater than 2/P and less than critical grazing angle, the angular dependency of bottom backscattering due to roughness seafloor is weighted by phase parameter of bottom reflection coefficient, while the intensity dependency is independent of phase parameter. At each small grazing angle, as grazing angle is less than 2/P, the angular dependency of bottom backscattering due to roughness seafloor is proportional to incident and scattering grazing angle squared and irrespective of phase parameter of bottom reflection coefficient which is like the empirical bottom backscattering model, while the intensity dependency is proportional to the fourth power of phase parameter. So the bottom has different influences on the angular dependency and intensity dependency of bottom backscattering in different stages of grazing angle.关键词
海底反向散射模型/强度特性/角度特性/小掠射角近似Key words
bottom sackscattering model/intensity dependency/angular dependency/small grazing angle approximation引用本文复制引用
侯倩男,吴金荣..浅海小掠射角的海底界面声反向散射模型的简化[J].物理学报,2019,68(4):230-238,9.基金项目
国家自然科学基金(批准号: 11374323, 11774375) 资助的课题. （批准号: 11374323, 11774375）
