An energy finite element formulation for high-frequency vibration analysis of externally fluid-loaded cylindrical shells with periodic circumferential stiffeners subjected to axi-symmetric excitation

A hybrid method is developed for predicting the high-frequency vibration response of fluid-loaded cylindrical shells with periodic circumferential stiffeners. In this method, the cylindrical shell is modeled using the Energy Finite Element Analysis (EFEA) method which includes added mass and radiation effects due to the surrounding exterior fluid medium. The joint matrices of the EFEA formulation at the location of the periodic stiffeners are computed based on Periodic Structure (PS) theory. Thus, the periodicity effects such as pass/stop characteristics are captured in the EFEA solution. The hybrid EFEA-PS method is used to analyze the vibration of a fluid-loaded axisymmetric cylindrical shell with periodic circumferential stiffeners. The flexural energy stored in each periodic section is computed. The results are compared with the solution produced by a very dense axisymmetric Finite Element (FE) model with infinite finite elements for the fluid domain. The good correlation indicates that the new hybrid method captures properly both the heavy fluid effects of the exterior fluid medium and the periodicity characteristics due to periodic stiffeners.