外壳板采用纵骨加强的双层加肋圆柱壳水下声辐射分析

建立了外壳板加纵骨的双层加肋圆柱壳水下声辐射计算方法，计算模型采用Donnell壳体理论，考虑了环肋、舱壁和实肋板对内外圆柱壳的径向、切向、纵向反作用力以及纵向反弯矩，利用傅氏变换和模态展开在波数域建立了计算模型的声弹耦合控制方程。推导了所有结构部件以及水介质的速度阻抗表达式，采用数值计算方法在波数域求解出径向振动速度，利用稳相法得到远场辐射声压。研究表明，如果纵骨沿圆周均匀排列，则纵骨的存在不导致圆柱壳周向模态耦合，纵骨加强的双层圆柱壳水下声辐射计算可以大大筒化。采用文中方法研究了环频率以下外壳板加纵骨的双层加肋圆柱壳水下声辐射特性，计算表时：在较低的频率段，外壳板采用纵骨加强使双层加肋圆柱壳水下辐射声压增大；增大纵骨刚废，结构辐射声压也相应增大；纵骨间距对双层加肋圆柱壳水下声辐射影响比较复杂，辐射声压谱随纵骨间距变化较大，而总声级变化不明显。

Acoustic Radiation from Fluid-loaded Infinite Circular Cylindrical Double-shell Reinforced by Transverse and Axial Stiffeners

This paper builds a method to calculate underwater radiation from circular cylindrical double shells reinforced by transverse and axial stiffeners excited by three (longitudinal, circumferential and axial) concentradted loads. The analytic model adapts Donnell shell theory, considers three (longitudinal, circumferential and axial) reacted forces and longitudinal moments of all structural components (including rings, bulkheads and brackets) acting on double shells. Fourier transform and mode expansion technologies are adapted to formulate the acoustic and elastic structure coupling equation. The dynamic equilibrium equations of the plate and ring are also studied, which involve flexible and inplane vibration. By utilizing harmonious displacement condition between plates (or rings) and double shells, this paper derives the velocity resistance expressions of all structural and liquid components. Numerical method is used to solve radian velocity of the outside shell in wavenumber domain, and radiated sound pressure in far field is obtained by stationary phase approximation. The research in this paper demonstrates that the stringers do not result in the coupling of circumferential modes, if stringers are arranged evenly around the circular, for the non diagonal elements in resistant matrix of stringers are nearly zero comparing with the diagonal elements, which greatly simplifies the calculation of radiation from the double shell with the outside shell reinforced by stringers. Existed methods calculating the underwater readiation of a stiffened double shell only consider radian reacted force of uneven structure components, which is a much simplification of real structure. The characteristics of underwater radiation from circular cylindrical double shells under ring frequency is also investigated using the method mentioned. Computed results show that at lower frequency, stringers attached at the outside shell produce more radiation, the radiated sound pressure enhances with the rigidity of stringers increasing and stringer space exhibits a complicated effect on the radiation of the double shell, the radiated sound pressure spectrum varies with stringer space, and the total sound pressure level is nearly unchanged.