Flexural–torsional vibration reduction of an eccentric phononic crystal pipe conveying fluid

Abstract

Flexural vibration and torsional vibration pervasively exist in slender structures, which often lead to noise emission and fatigue failure of structures. In order to effectively suppress coupled flexural–torsional vibrations of defective devices transporting fluid, this paper introduces an eccentric fluid-conveying pipe axially made of periodically varying materials, and the flexural–torsional bandgap (BG) characteristics of such phononic crystal pipe system are investigated. With consideration of warping effect, coupled flexural–torsional motion equations are established. The complex band structure of sub-structure and frequency response function and attenuation configuration of topological structure are attained by applying the spectral element method. In comparison with literatures only yielding total merging BG of flexural and torsional vibrations, this paper presents a novel result of completely separate flexural BG and torsional BG, which enables individual manipulation of the two elastic waves. Meanwhile, broadband frequency BGs are harvested in the proposed pipe structure, especially for torsional vibration, demonstrating an excellent vibration isolation property. Complicated regulation mechanism of eccentric, warping effects and some critical parameters is explored. This study is expected to provide a new approach for flexural–torsional vibration reduction of engineering fluid-transporting devices.