Modelling and analysis of vortex induced vibration in marine risers

Abstract

Marine Risers that are used to extract crude oil from the seabed to offshore platforms are subjected to Vortex-Induced Vibrations (VIV) in interaction with the external fluid flow of seawater. The study of VIV is essential as it plays a crucial role in designing marine risers. This paper focuses on creating a two-dimensional numerical simulation of a circular cylinder of Marine Riser which is exposed to different current velocities to estimate parameters such as Lift coefficient, Drag Coefficient, and Shedding frequency of VIV. The shedding frequencies obtained from the numerical model are compared with the natural frequencies of the riser to get the lock-in condition of the riser which ultimately gives rise to VIV. In addition to this, an analytical model is developed to find out the natural frequencies of the risers. Hence the vortex-induced vibrations in the lock-in region can be reduced by increasing the tension which should be within the maximum over pull.