Three-dimensional modeling and bandgap performance of a rotating phononic crystal pipe conveying fluid

Vibration and noise reduction of motional structures is a conventional challenge in a variety of industrial realms due to synchronous spatial motions present. In this case, optimizing structure design could provide a promising way for solution. Motivated by the idea of wave manipulation via phononic crystals (PCs), this paper aims to control three-dimensional (3D) vibration transmission of a rotating pipe by introducing an axial periodic design. The pipe is arranged as a composite structure comprised of alternate materials along the axial direction, and a constant fluid flows inside the pipe. Based on the Rayleigh beam theory, a set of 3D doubly-gyroscopic equations governing in-plane, out-of-plane flexural and axial motions of the pipe is established, which accounts for rotation gyroscopic force and fluid gyroscopic force. The spectral element technology is applied in such multi-dimensional system for solution. Following a validation by the finite element (FE) simulation, the band structure, frequency response function (FRF) and elastic wave shapes are presented to elucidate the 3D bandgap (BG) mechanism of the rotating PC pipe. The results obtained demonstrate the superior effectiveness of the proposed model for the 3D vibration suppression. Extensive parametric discussions reveal that the rotating motion, flowing fluid and geometry of the pipe all have significant impacts on the BG performance of the present rotating PC pipe system.