Acoustic Infinite Element Method And Its Application On The Acoustic Prediction Of Underwater Structure

In the field of computational structural acoustics, the problem of efficiently modelingacoustic field in unbounded domains has received a significant challenge for over a quartercentury. Many techniques have evolved including boundary element method(BEM),approximate boundary condition and acoustical infinite element method. Especially, infiniteelement method has been performed excellent computational capability to the actuallyapplications on engineering structures with huge computational matrix size,thus, it has beenarised the most attention in the literature.BEM remains for a long time as the method of choice by most researchers and codedevelopers, due to its advantage of the reduction of the dimensionality of the problem by oneand the consequent reduction in the number of discretized equations to solve, leading to theincrease on the computical efficiency. However, BEM has a severe disadvantages because ofthe much greater bandwidth of the equations due to its inherent nonlocal connectivity, so itsnot still efficient to solve problems of engineering structures with enormous intergral surfaceby BEM. While the infinite element method model the acoustic field with a truncated artificialboundary surrounding the structure and a infinite acoustical element is posed on artificialboundary. The method retains one advantage of finite element method that coefficient matrixis sparse, on the other hand, it significantly reduces the amount of finite acoustical field, sothat infinite element method can be a better choice verse BEM for complex engineeringproblem.Although a series of infinite element methods are developed to account for variousresearch objects and engineering background, we mainly focus on Astley wave envelopemethod of and Burnett oblate spheroidal acoustic infinite method, this paper mainly involvesthe following aspects：Based on the theory of wave envelope method, the variable order infinite wave envelopemethod for acoustic radiation and scattering are presented in the paper, differenttwo-dimensional and axisymmetric acoustic radiation and scattering problems have beeninvestigated to verify the validity of the method, and the effects of different parameters suchas virtual source are also discussed.Using of acoustic impedance theory and infinite element method, the effects of artificial truncated scale on the typical shells and cylindrical shells are investigated, which can providea reference for the practical engineering numerical calculations.Ellipsoidal acoustic infinite element method is presented in five chapter, the calculationaccuracy and convergence of the method is studied, the effects of shape functions, order ofshape functions and scale of the artificial boundary are discussed, besides, we also comparethe accuracy and calculation efficiency of a variety of approximate boundary conditions andtwo versions of an infinite element method.The acoustic infinite element method is applied to acoustic calculation of complexdouble cylindrical shells, we mainly studies the influence of fluid-structure interaction effectsand different parameters of the shells on the vibration and sound radiation characteristics.