Numerical study on the characteristics of vortex-induced vibrations of a small-scale subsea jumper using a wake oscillator model

Abstract

Vortex-induced vibrations (VIVs) of a small-scale subsea jumper has been studied numerically using a wake oscillator model. The dynamics of the jumper is described based on the linear Euler–Bernoulli beam theory and a wake oscillator model is uniformly distributed along the jumper to model the hydrodynamic force acting on it. The dynamics of the coupled system has been solved using the finite element method and the responses of the jumper subjected to uniform flows in different directions have been analysed. Some important characteristics of jumper VIVs, such as multi-frequency multi-mode response, single-frequency multi-mode response as well as uncoupled cross-flow and in-line VIVs without dual resonance, have been identified and the underlying mechanism have been explored. One unique character of the jumper mode is that some segmental elements of the jumper would undertake significant rigid body motions in their axial directions. A qualitative comparison shows that these axial rigid body motions of the segmental elements may influence the hydrodynamic force and could play an important role in the reliable prediction of the jumper VIV.