Abstract:Existing research has indicated that both fluid-structure coupling (incompressible fluid) and acoustics-structure coupling (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.Building upon this prior research, this study further investigates the impact of fluid compressibility on low-frequency forced vibrations within a coupled system. It separately derives the coupled vibration equations for cylindrical shell structures in compressible and incompressible fluid fields and calculates their respective forced vibration responses. 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; notably reducing peak vibration response levels 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 coupling 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.
