Abstract: The structure of elastic tube bundles and the fluid inside constitute a typical fluid-structure interaction system. The governing vibration equation of the system is derived from the displacement-pressure format and the finite element models are built by considering the compressibility of the fluid. Natural frequencies and modal shapes of the structure, the fluid inside and the structure-fluid system are calculated separately. The results show that not only the natural frequencies and mode shapes of the original structure and fluid are changed due to the interaction between fluid and structure, but also one subsystem is forced to vibrate in a particular pattern corresponding to the vibration of the other subsystem. The effects of fluids with different densities on the structure are also different. The influence of fluid-structure interaction must be taken into account when the dynamic response of elastic tube bundles is studied.

Key words: elastic tube bundles, fluid-structure interaction, modal analysis, finite element method