# Fluid-structure coupling of concentric double FGM shells with different lengths

## TL;DR

This paper develops a semi-analytical method to study fluid-structure interaction in concentric double shells made of functionally graded materials, revealing mode-specific coupling and frequency behaviors as material gradients vary.

## Contribution

A novel semi-analytical approach for fluid-structure coupling in concentric FGM shells with different lengths and elastic properties is introduced and verified.

## Key findings

- Coupling occurs only when shells vibrate in the same circumferential mode.
- Normalized vibration amplitudes are similar for narrow gaps.
- Natural frequencies decrease and converge with increasing gradient index.

## Abstract

The aim of this study is to develop a semi-analytical method to investigate fluid-structure coupling of concentric double shells with different lengths and elastic behaviours. Co-axial shells constitute a cylindrical circular container and a baffle submerged inside the stored fluid. The container shell is made of functionally graded materials with mechanical properties changing through its thickness continuously. The baffle made of steel is fixed along its top edge and submerged inside fluid such that its lower edge freely moves. The developed approach is verified using a commercial finite element computer code. Although the model is presented for a specific case in the present work, it can be generalized to investigate coupling of shellplate structures via fluid. It is shown that the coupling between concentric shells occurs only when they vibrate in a same circumferential mode number, n. It is also revealed that the normalized vibration amplitude of the inner shell is about the same as that of the outer shell, for narrower radial gaps. Moreover, the natural frequencies of the fluid-coupled system gradually decrease and converge to the certain values as the gradient index increases.

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Source: https://tomesphere.com/paper/1905.00879