| 摘要: |
| 运用表面helmholtz积分公式研究柱目标位于不同阻抗界面附近的声散射。根据Green函数的定义，在两维空间中，应用Fourier变换方法，将柱面波展开成平面波的迭加，并用越过法求解柱面波在界面上的声反射；同时定义扩展反射系数描述柱面波在平面上的反射大小，从而获得二维半无限空间Green函数的表达式。以刚性圆柱在界面附近的声散射为例进行计算，得到不同于自由场目标的散射特性，即界面附近目标的反向散射形态函数具深度起伏；除垂直界面入射外，散射指向性呈非对称特性。 |
| 关键词: 目标反射 刚性柱 数值方法 |
| DOI： |
| 分类号: |
| 基金项目:国防科技预研基金项目，91J3.02 |
附件 |
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| SOUND SCATTERING OF CYLINDRICAL WAVE FROM A TARGET NEAR A PLANE BOUNDARY SURFACE |
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Xu Haiting
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Qingdao Acoustics Laboratory, Chinese Academy of Sciences, Qingdao 266023
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| Abstract: |
| The Boundary Helmholtz Integral Formula is developed to compute the field scattered from a cylinder near a plane boundary surface with varied impedance in this paper. The key problem is to derive the Green function. According to the definition of the Green function and the image principle of optics, the Green function Gh in a half space with boundary surface s is composed of two parts, Gh=G+G', G is the direct sound field, G' depends on s and can be considered as the field of the image source symmetric about s. For a two-dimension half space, a cylindrical wave is expanded in superposition of plane waves by using the Fourier Transformation method, and Steepest Descent Method is used to find the reflection of the cylindrical wave. The extended reflective coefficient V(θ) representing the intensity of the image is defined to express the reflection of a cylindrical wave, V(θ)=v(θ) - iv'(θ)/2kr, where v (θ) is the reflection coefficient of a plane wave. The Green function in a two-dimension half space is Gh(r)=G(r)+V(θ)*G(r)'.
As example, the scattering computations are made for a rigid long cylinder near a plane boundary surface. The results indicated that the fluctuation of the form function of the back scattering from the cylinder in a half space is stronger than that in a free field. Except the vertical incident on s, directivity of the scattering sound is not symmetry. |
| Key words: Sound reflection, Rigid cylinder, Numerical method |
