【作者】 黎胜；

【导师】 赵德有；

【作者基本信息】 大连理工大学 ， 船舶与海洋结构物设计制造， 2001， 博士

【摘要】 水下结构声辐射和声传输的数值分析和主动控制研究，具有重要的理论意义和应用前景。基于数值模拟对舰船结构进行振动噪声的设计控制，能使舰船结构具有良好的动态特性，满足舰船低振动、低噪声的设计要求。而对水下结构振动声辐射和声传输主动控制的深入研究，以及将主动控制方法与被动控制方法相结合，应能够彻底地解决舰船结构的振动噪声问题。本文采用数值方法对水下结构声辐射和声传输及其主动控制进行了计算研究，现将论文的主要研究内容及创新性成果叙述如下： 采用边界元法以脉动球为例计算研究了自由表面对结构声辐射的影响，指出在低频和自由表面距离结构较近时，自由表面对结构声辐射有较大影响，自由表面存在大大减小了结构的辐射声功率，此时必须考虑自由表面对结构声辐射的影响。 采用有限元法和基于表面Rayleigh积分的边界元法对无限障板中的加筋板和复合材料层合板，建立了在低频简谐平面声波斜入射情况下，声波由空气经结构向水中传输的计算模型，并利用该模型计算研究了加筋板和复合材料层合板的声传输特性。数值计算表明：当声波从空气经结构向水中传输时，当板的刚度较小时，空气和水两种流体介质间的特性声阻抗失配对声传输起了支配作用，此时板的刚度相对而言显得并不重要。但当板的刚度较大时，板的刚度对声传输也有较大影响。对复合材料层合板结构声传输的研究表明，即使在相同材料、相同层数和相同厚度情况下，不同的铺设角度和铺设方式仍会对层合板的传声损失产生较大影响，这在复合材料结构声学设计中是值得注意的。 采用有限元法和边界元法建立了复杂结构声辐射的振动模态分析模型和辐射模态分析模型。研究了振动模态间的耦合对辐射声功率的影响，指出振动模态间的耦合可能会增大结构辐射声功率，也可能会减小结构辐射声功率，或对辐射声功率没有影响。而且，当振动模态间的耦合作用对辐射声功率的影响不大时，采用振动模态控制可取得较好的减振降噪双重控制效果。基于所建立的任意复杂结构声辐射的辐射模态分析模型，对正方形封闭空间结构的声辐射进行了辐射模态分析，给出了正方形封闭空间结构的辐射效率和辐射模态形状。 基于有限元法和边界元法，采用负速度反馈控制，对水下含压电层和粘弹性层层合板的振动声辐射和声传输进行了主动阻尼控制和主被动阻尼控制研究。数值模拟表明，主动阻尼控制和主被动阻尼控制能有效地降低板的均方速度和辐射声功率，特别是主被动阻尼控制有着非常好的阻尼控制效果。可较好的抑制结构的振动声辐射。更多还原

【Abstract】 Numerical analysis and active control of underwater structural acoustic radiation and transmission are very important for achieving quiet submerged structures. First, the design procedures such as simulation-based-design and vibration-and-noise-control-by-design for achieving a quiet submerged structure are based on the numerical analysis of response behavior of the submerged structure. Second, active structural acoustic control has emerged as a very promising method to reduce structural radiated noise at low frequencies and has been found to be complementary to passive control methods, which are good at high frequencies. This dissertation addresses a detailed study of numerical analysis and active control simulation of underwater structural acoustic radiation and transmission. The major contributions of this dissertation are as follows:Based on the boundary element formulation of half-space radiation, the effect of a free surface on acoustic radiation from a sphere is discussed. It is shown that the free surface has significant influence on acoustic radiation when the sphere is near the surface in the low frequency range. The presence of the free surface reduces the acoustic power radiated by the sphere significantly.A computational model of sound transmission from air to water through a stiffened plate or a composite laminates excited by a harmonic oblique incident plane wave and mounted in an infinite baffle is presented. Finite element method (FEM) is used to model the structures. Boundary element method (BEM) based on the Rayleigh integral in the plate surface is employed for the acoustic fluid. The sound transmission losses through the stiffened plate and the composite laminate are discussed with the proposed model. The numerical results show that the influence of the stiffness of the structures on sound transmission from air to water is important only if the structures’ stiffness is very large, and the big difference of characteristic acoustic impedance between air and water dominates the sound transmission when the structures’ stiffness is small. The influence of different stacking sequences such as symmetric angle-ply, anti-symmetric angle-ply and cross-ply on the sound transmission losses of the laminated composite plates is evaluated too with the proposed model. The results indicate that the laminate stacking geometry may have a significant influence on the sound transmission losses of laminated composite plates and the designers must be careful when deciding on the stacking sequences.-11 -AbstractA vibration modal approach and a radiation modal approach are proposed to analyze acoustic radiation from structures with complex geometries using FEM and BEM. The power radiated by vibration modes is discussed. It is shown that the power radiated by a vibration mode alone is to increase total radiated power and the interaction of different vibration modes can lead to an increase or a decrease or no change in the total radiated power, moreover, control of the vibration modes will be a good way to reduce both vibration and radiated sound as long as the influence of the interaction of the vibration modes on sound radiation is insignificant. In the presented radiation modal approach the CHIEF method is adopted to obtain a radiation mode formulation for extehor acoustic radiation analysis of three-dimensional structures without the nonuniqueness difficulty at critical frequencies. A pulsating cube is involved to demonstrate the radiation modal analysis procedure. The shapes and radiation efficiencies of the radiation modes of the cube are studied.Based on the Lagrangian of a piezoelectric body, a vanational equation of a piezoelectric structure is derived by using Hamilton’s principle. Then, a finite element formulation of a laminated plate integrated with piezoelectric layers and viscoelastic layer is developed on the basis of the vanational equation for modeling the coupled electroelastic behavior using the Mindlin plate theory. After then, boundary element formulation based on the R更多还原