浸没圆柱壳振动性能计算耦合模型对比研究

Comparative Study of Coupled Models for Vibration Performance Calculation of Submerged Cylindrical Shells

摘要:

已有研究表明，使用流固耦合（流体不可压缩）和声固耦合（流体可压缩）模型，均能推导浸没于无限水域中圆柱壳结构的耦合振动方程；同时，在低频范围内对两类方程求解，耦合系统同阶次固有频率计算结果无明显差异。在以上研究基础上，进一步分析流体压缩性对耦合系统中低频段受迫振动的影响， 分别推导可压/不可压流场下圆柱壳结构耦合振动方程，并求解其受迫振动响应。研究结果表明，流体可压时， 可用复数附连水质量的概念来阐述流体压缩性带来的阻尼效应。此外，激励频率较低时，阻尼效应比较微弱， 2 类模型振动响应较为一致；随着激励频率增大，阻尼整体上呈增大趋势，声固模型相比流固模型的振动响应峰值有明显削弱。基于以上结果，在进行流固耦合振动性能计算分析时，工程研究人员可选用计算代价较小的流固耦合分析模式，并对流体质量矩阵进行修正以考虑流体压缩性带来的阻尼效应，从而使计算代价与计算精度得到平衡。

Abstract:

Existing research has indicated that both fluid-structure interaction（incompressible fluid）and acoustics-structure interaction（compressible fluid）models can be used to derive the coupled vibration equations for cylindrical shell structures submerged in an infinite water domain. Furthermore，within the low-frequency range， there is no significant difference in the calculated results of the same-order natural frequencies of the coupled system when using either type of equation. On the basis of the above research，the influence of fluid compressibility on low-frequency forced vibrations within a coupled system is further analyzed. The coupled vibration equations for cylindrical shell structures in compressible and incompressible fluid fields are derived respectively，and the forced vibration response is solved. The findings reveal that when dealing with compressible fluids，it is possible to explain the damping effect resulting from fluid compressibility through a concept involving complex attached water mass. Moreover，at lower excitation frequencies，Rayleigh damping effects are relatively weak and both model types exhibit consistent vibration responses. As excitation frequency increases，overall damping tends to rise，and peak vibration response levels reduce notably in acoustic-structure models compared to those in fluid-structure models. Based on these outcomes，engineering researchers may opt for computationally less expensive fluid-structure interaction analysis models during assessments of vibrational performance. They can then adjust the fluid mass matrix to account for dampening effects arising from fluid compressibility，thus achieving a balance between computational cost and precision.