Investigating cross-flow vortex-induced vibration of top tension risers with different aspect ratios

Abstract

The vortex-induced vibration (VIV) of marine risers with large aspect ratio (length-to-diameter ratio) is a very complicated fluid-structure interaction phenomenon, which is the main cause of fatigue failure of marine risers. In order for the safe and stable operation of the riser systems, it is crucial to investigate the effect of the aspect ratio on the VIV response of the risers. In this study, the cross-flow VIV characteristics of a top tension riser with different aspect ratios are analyzed using a time domain simulation method. First of all, a riser model considering the fluid-structure interaction was established to calculate the natural vibration characteristics and compare with the theoretical result. Then, the cross-flow VIV response of the riser model in uniform and shear flows were respectively calculated and compared with the results of an experimental model. The numerical results were in good agreement with the experimental results. Subsequently, the developed riser model can be used to predict the cross-flow VIV response with different aspect ratios. Finally, the effects of the model scale and aspect ratio on VIV response were analyzed. The analysis results may provide a basis for selecting appropriate model scale and aspect ratio in establishing the riser simulation model.