基于解析法的水下环肋圆锥壳声振特性研究

发布时间：2018-11-24 08:26

【摘要】：水下潜器艉部可用环肋圆锥壳近似模拟,锥壳结构声振特性的研究,对于潜器艉部噪声控制有着重大的科学与工程意义。本文提出了水下环肋圆锥壳在低频、典型和弹性边界条件下的自由振动与受迫振动声辐射的解析方法,研究了水下环肋圆锥壳低频时的声振特性。首先在环肋圆锥壳肋骨和壳体结合处将壳体划分成多个子结构。采用Flügge理论描述锥壳分段的运动方程,位移函数表达为幂级数的形式。通过将锥壳划分成多个窄的分段,并将每个分段局部等效为柱壳,来考虑流体负载的影响。将环肋离散处理并用圆环板运动方程进行描述。然后,由边界条件和相邻子结构间的连续条件形成最终求解环肋锥壳振动的刚度矩阵,采用单元辐射叠加法求得壳体远场声压。将文中解析法计算结果与有限元法或已有文献中计算结果对比,验证了本文解析法的正确性。随后用解析法研究了水下环肋锥壳自由振动特性。研究了流体负载、边界条件、半锥角、厚度、锥壳长度及环肋尺寸等对典型边界条件下环肋锥壳自由振动特性的影响,并研究了锥壳结构参数对弹性边界下锥壳基频和梁频的影响。最后,在研究自由振动特性的基础上,分析了结构参数、流体负载等对环肋锥壳声振特性的影响,考虑了垂向激励、纵向激励、对称/非对称激励及偶极子源激励分别作用下锥壳声振特性并与圆柱壳声振特性作对比。总的来说,本文采用圆环板处理环肋,相对于“平摊法”、能量法等精度更高,适于处理任意布置的环肋;大多数相关文献主要研究典型边界条件下壳体的振动特性,而文中对弹性边界条件下圆锥壳的自由振动特性给出了详细的分析,可为壳体截断处边界条件选取这一工程实际问题提供理论指导;本文还详细对比了圆锥壳与圆柱壳声振特性,分析了半锥角对结构声振特性带来的影响,对潜器艉部螺旋桨-轴-艇噪声这一工程问题,从机理上详细分析了结构参数对锥壳声振特性的影响,并将偶极子源激励与力激励对比,为螺旋桨直接辐射噪声和桨轴激起艇体的振动噪声大小排序提供理论依据,研究结论可为水下潜器艉部结构声学设计提供理论指导。
[Abstract]:The stern part of underwater vehicle can be simulated approximately by ring rib conical shell. The study of acoustic and vibration characteristics of conical shell structure is of great scientific and engineering significance for the noise control of the stern part of underwater vehicle. In this paper, an analytical method of acoustic radiation from free vibration and forced vibration of underwater ring rib conical shell under low frequency, typical and elastic boundary conditions is presented. The acoustic vibration characteristics of underwater ring rib conical shell at low frequency are studied. Firstly, the shell is divided into several substructures at the joint of the ring rib conical shell and the shell. The Fl 眉 gge theory is used to describe the motion equation of the conical shell, and the displacement function is expressed in the form of power series. The conical shell is divided into several narrow segments and each segment is locally equivalent to a cylindrical shell to consider the effect of fluid load. The ring rib is discretized and described by the toroidal plate motion equation. Then, the stiffness matrix of the ring rib conical shell vibration is formed by the boundary condition and the continuous condition between adjacent substructures, and the far field sound pressure of the shell is obtained by using the element radiation superposition method. The correctness of the analytical method is verified by comparing the results of the analytical method with that of the finite element method or the existing literatures. Then the free vibration characteristics of underwater ring rib conical shell are studied by analytical method. The effects of fluid load, boundary condition, half cone angle, thickness, length of conical shell and size of ring rib on the free vibration characteristics of ring rib conical shell under typical boundary conditions are studied. The influence of the structural parameters of the conical shell on the fundamental frequency and beam frequency of the conical shell with elastic boundary is studied. Finally, on the basis of studying the characteristics of free vibration, the effects of structural parameters and fluid load on the acoustic and vibration characteristics of ring rib conical shell are analyzed, and vertical and longitudinal excitation are considered. The acousto-vibration characteristics of conical shells under symmetric / asymmetric excitation and dipole source excitation are compared with those of cylindrical shells. In general, the ring rib is treated by ring plate, which is more accurate than "equalization method" and "energy method", so it is suitable for dealing with arbitrarily arranged ring rib. Most of the related literatures mainly study the vibration characteristics of the shell under the typical boundary condition, and the free vibration characteristics of the conical shell under the elastic boundary condition are analyzed in detail in this paper. It can provide theoretical guidance for the selection of boundary conditions at the truncation of the shell. In this paper, the acoustic and vibration characteristics of conical shell and cylindrical shell are compared in detail, and the influence of the half cone angle on the acoustic and vibration characteristics of the structure is analyzed, and the engineering problem of the stern propeller-axle-boat noise of the submersible is also discussed. The influence of structural parameters on the acoustic and vibration characteristics of conical shell is analyzed in detail from the mechanism, and the dipole source excitation is compared with the force excitation, which provides a theoretical basis for the direct radiation noise of propeller and the ranking of vibration noise caused by propeller shaft. The conclusions can provide theoretical guidance for acoustic design of stern structure of underwater vehicle.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U661.44

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