Computation And Analysis On The Scattering Fields Of Underwater Rigid Objects Based On The T-matrix Method

As an important embranchment of acoustics, underwater acoustics is developed since World War II. The research areas of underwater acoustics involve the generate,transmit and receive of the sound wave which contains some kinds of information. As the development of the science technology and the requirement of mankind to the ocean resources, the ocean exploitation is focused on nowadays. So underwater acoustics is unprecedented developed now.The thesis uses the T-matrix approach to study the philosophy of acoustic scattering and to compute the scattering field. The philosophy of the T-matrix approach is to expand all field quantities in terms of a set of spherical functions in order to obtain the T matrix that relates the known coefficients of expansion of the incident plane harmonic wave to the unknown expansion coefficients of the scattered field. The T-matrix method is applied to compute scattering from rigid structures that are underwater. The T-matrix method was originally introduced by PC.Waterman, it is conveniently and suited to all sharps of rigid structures that are underwater. In the unceasingly developing, the T-matrix method is also applied to the computation of scattering of the electromagnetic field. Based on the T-matrix method, this thesis studies further on this method.. The first chapter presents the origin and meaning of the topic, the domestic and international research background is introduced too. The second part of the paper introduced the T-matrix method in detailed, and applied the approach to the axisymmetric scatter of ellipsoid. At the end of this chapter, it gives the amplitude of acoustic scattering field as the function of the non- frequency and the function of the scattering angular. Additionally, to explain the physical meaning of the figure of the scattering field, the intervene model of the reflect wave and creeping wave is built. Based on the knowledge we learnt in chapter 2, chapter 3 will analyze and solve a computational problem that comes from applying the T-matrix to slender structures. The improved and the unimproved results have been compared to shown that the new method is effective. And the end part of the chapter also shows the amplitude of acoustic scattering field from cylinder with spheroidal endcaps using the new algorithm. The forth chapter firstly introduce briefly about acoustic scattering field of two rigid underwater scatters, and then the paper will show the process of how to extend the T-matrix method to the computation of scattering of two underwater scatters. The acoustic scattering field of two rigid underwater scatters is presented. The last part gives a summarization of the paper.