Sound Field Modeling And Calculation For Underwater Acoustic Projecting Transducer And Array

This thesis first studies the main characteristics of the sound radiation of various typical sources, then studies the fundamental theory of the boundary element method, at last carefully studies the modeling and calculation of the acoustic radiated field of underwater acoustic projecting transducers and arrays by using the boundary element method. The main research contents and results are as follows:(1) The general concept of acoustic radiation and the analytic calculation of the sound radiation of several typical sources are carefully studied after the fundamental contents of linear acoustics are studied. The relationship between the radiation impedance and the acoustic radiated power of the radiator with non-uniform vibrating velocity on the surface is formulated. And the analytic calculation method of the self radiation impedance and mutual radiation impedance of the transducer array is studied.(2) The method of using boundary element model to solve the acoustic radiation problem of the vibrating body is studied. The boundary integral equation is derived, which includes the exterior Helmholtz integral equation, surface Helmholtz integral equation and the interior Helmholtz integral equation. The numerical calculation problem of the boundary element method is studied, which includes using quadratic interpolating shape function, solving the singular integral and solving the non-uniqueness of the solution. And also several special problems of the acoustic radiation are studied which are the half-space problem, the baffled problem and the asymptotic formulation of the acoustic radiation at high frequency.(3) The commercial software SYSNOISE which is based on the boundary element method is used to calculate the acoustic radiated field and radiation impedance of various sources. First the function and the using method of the SYSNOISE software is studied. Then the acoustic radiated field and the radiation impedance of several typical sources are calculated by using the boundary element method, and the results are compared to the analytic solutions. The numerical solutions fit the analytic solutions very well, which indicates the reliability of the calculation accuracy of the boundary element method. At last, The acoustic radiated field and radiation impedance of various transducers and arrays are calculated, whichinclude the conformal array on the head of the AUV.(4) The boundary element theory together with optimization method is used to calculate the vibration velocity weighting vector of the underwater acoustic projecting transducer array for an expected beam pattern. At first, the relationship between the acoustic radiated field and the vibration velocity weighting vector of the array is formulated. Then two weight calculation methods are presented, i.e. the phase compensation method and the least 2-norm method in which the acoustic mutual effect of the baffle and the transducers are considered.