外部加环肋圆柱壳声散射数值和试验研究（英文）

Numerical and Experimental Studies of the Acoustic Scattering from an Externally Ring-Stiffened Cylindrical Shell

双层壳体声散射特性研究对水中目标探测和识别具有重要意义。文章基于混合2-D/3-D有限元法对外部加环肋圆柱壳声散射进行数值建模,基于薄壳理论推导近似解析表达式对周期加肋圆柱壳的角度频率谱中Bragg散射和Bloch-Floquet弯曲波共振散射进行理论预报,并进行水池试验验证。与平板情况相比,圆柱薄壳中存在弯曲波a0、压缩波s0和剪切波T0三种弹性波,弯曲波对Bloch-Floquet波共振散射有重要作用。外部环肋板不仅通过影响壳体振动间接影响外部散射声场,而且作为散射子结构通过与外部流体耦合直接参与散射。与解析方法和物理声学方法相比,混合2-D/3-D有限元方法充分考虑了结构弹性、肋板与圆柱壳体之间的遮挡和多重散射效应,以及肋板与水的耦合作用,具有计算准确、高效等优点,能较好地解决复杂结构的中低频振动-声耦合问题。

Studying the interaction of sound with double shells immersed in water is essential for improving existing underwater target detection and classification algorithms.To identify the key physics,a hybrid 2-D/3-D finite element modeling technique was employed to calculate and analyze the acoustic scattering from an externally ring-stiffened cylindrical shell.Approximate analytical expressions were explicitly derived to identify Bragg and Bloch-Floquet wave scattering in frequency-angle spectra.Monostatic scattering measurements were performed for validation.In contrast to the case of a plate,there are three kinds of elastic waves in a thin cylindrical shell:the flexural wave a0,compressional wave s0 and shear wave T0.The flexural wave makes an important contribution to Bloch-Floquet wave scattering.The rings indirectly influence the exterior acoustic scattered field through the dynamic response of the shell,and serve as direct acoustic scatterers that increase the target cross section,especially at oblique incidence.For the external rings at an incident angle of 45°,the geometrical scattering is enhanced due to their influence as corner reflectors.Compared with the analytical method and physical acoustic method,the hybrid 2-D/3-D FE method considers the elasticity of structure,the occlusion and multiple scattering between the rib and the shell,and the interaction between the rib and the water.It has the advantages of high computing efficiency and accuracy,which is suitable for the structural-acoustic coupling analysis of complex stiffened structure in low and middle frequency.