A single wake oscillator model for coupled cross-flow and in-line vortex-induced vibrations of marine structures

Abstract

Vortex-induced vibration (VIV) is awell-known phenomenon for civil and offshore structures. Currently, the prediction of this type of vibration in practice currently mainly relies on the force-decomposition method. However, the limitations of this method have restricted the applicability of the method, and alternative models are therefore needed to meet increasing demands for the more accurate prediction of VIV under more complicated conditions. The wake oscillator model overcomes the main limitations of the force-decomposition method to some extent, and it is one of the promising models that has gained popularity in recent years. Although the concept of the wake oscillator was first proposed over half a century ago and has been developed much since then, the existing wake oscillator models still have some limitations, which have restricted their applications. The main objective of this study is to improve the wake oscillator model for better modelling of the VIV of cylindrical structures, and efforts are made in this thesis to (a) reproduce the free and forced vibration experiments by introducing nonlinear coupling, and (b) develop a single wake oscillator equation that is coupled to both cross-flow and in-line motions for the prediction of coupled cross-flow and in-line VIV...