Dynamic Characteristics of Cylindrical Shells Considering FSI

There are many finite element models used for assessing the structural integrity of cylinders or shells with fluid-filled annulus. In the past the fluid region was not modeled explicitly and their mass was added to the structural mass as a form of an added mass for simplicity. In this case the fluid-structure interaction effect, so called annulus effect, is not considered in the analysis, generating the unrealistic or unconservative results in some cases. Therefore it is necessary to make a 3-dimensional model including fluid region and to couple two nodes which are assigned to the fluid and the structure. Fortunately commercial programs such as ANSYS can model couplings between the fluid and the structure easily and can consider the annulus effect for various types of analyses very efficiently. Therefore in this study, theoretical background and several finite element models are developed for coaxial cylindrical shells with fluid-filled annulus considering fluid-structure interaction. The effect of the inclusion of the fluid-filled annulus on the natural frequencies is investigated by comparing frequencies between various finite element models. Using the modal characteristics, typical dynamic analyses such as responses spectrum, power spectral density (PSD) and unit load excitation are performed and their response characteristics are addressed with respect to the various representations of the fluid-structure interaction