Nonlinear Forced Vibration of Spinning Pipes Conveying Fluid Under Lateral Harmonic Excitation

Abstract

As a crucial offshore drilling equipment, the drill strings often encounter instability due to various external excitations. In order to deeply understand the dynamical mechanism of such issues, in this paper, the working drill strings are modeled as a spinning pipe conveying fluid, and the forced vibration characteristics of such system under an equivalent lateral excitation are studied analytically and numerically. The system considered is essentially under triple excitations: the fluid–structure interaction (FSI), spinning motion and external force. The viscoelastic material and geometrical nonlinearity due to extensible pipe axis are taken into account. The governing equation is derived by the Hamilton principle and then treated by the numerical simulation. The Lissajous trajectory and whirling motion shape of the pipe are obtained, in which the subcritical and supercritical cases are both discussed. It is revealed that the system conducts periodic or quasi-periodic motion at subcritical state, while presents chaotic motion at supercritical flow velocity. Perturbation analysis is also carried out to investigate the nonlinear frequency–amplitude features of the system. Comprehensive parametric studies are performed and the flow velocity, spinning speed, nonlinearity, excitation and damping are all found to have significant effects on the moving trajectory and frequency response of the pipe.