Numerical investigation of Vortex-Induced Vibration response for a full-scale riser with staggered buoyancy modules

Abstract

Vortex-Induced Vibration (VIV) caused by ocean current is one of the main sources of the long-term fatigue damage of marine riser. Buoyancy module is an essential equipment for deep-water riser system, which can reduce the top tension remand. Based on the hydrodynamic force decomposition model and forced vibration test data, a time domain prediction model of VIV response for top-tensioned riser with buoyancy modules is established in this paper. Firstly, the numerical model is verified with the experimental measurements of an 11.48 m riser with buoyancy modules under uniform flow. Then, a 610 m riser is chosen as the research object, and five staggered buoyancy module configurations with different coverage ratios are simulated, to reveal the VIV response characteristics of full-scale riser with buoyancy modules. Some interesting phenomena are reasonably explained with VIV mechanism analysis. In terms of frequency response, displacement and modal order, the influence of coverage ratio on riser's VIV is analyzed. Finally, the optimal coverage of buoyancy modules for VIV suppression is discussed, which is of great significance in engineering application.