Improving time-domain prediction of vortex-induced vibration of marine risers

Abstract

The prediction of the vortex-induced vibration (VIV) of marine risers becomes a critical issue as the offshore exploration and production moving into deepwater and ultra-deepwater regions. In this paper, a time-domain model, based on a forcing algorithm and on high Reynolds number experimental data, was further developed to predict the VIV of rigid and flexible risers. The forcing algorithm was integrated into a global-coordinate-based finite-element program. At each time step, the hydrodynamic forces on a riser, including added mass, lift and drag forces, were calculated for each element based on two non-dimensional state variables—the amplitude ratio and the reduced velocity. The state variables were determined from a zero up-crossing analysis of the time history of the cross-flow displacement. Validation studies were carried out for a full-scale rigid riser segment in a uniform flow and a flexible riser in a stepped current. The predicted motions of the risers were compared with experimental data and the motions predicted by other numerical models.