Vortex-Induced Vibration Analysis (VIVA) Based on Hydrodynamic Databases

We outline the procedures used by program VIVA, developed over the last sixteen years to estimate the cross-flow vibration of marine risers in arbitrary currents. The program theory is based on a combination of first principles, extensive hydrodynamic databases, as well as modifications introduced through comparison against experimental and field data. The program was built from the start to handle standing as well as traveling waves, or arbitrary combinations of traveling and standing waves, through the use of complex modes. Considerable effort was expended to develop a hydrodynamic methodology that is suitable for short and long risers and cables, and which provides results in agreement with recent observed mechanisms. In particular, we outline changes to take into account: • the influence of in-line as well as cross-flow oscillations; • the influence of the Reynolds number; • the effect of high force harmonics; • modeling of lock-in in a sheared flow; • modeling of staked sections. The methodology is illustrated through several examples where predictions are compared with field and experimental data.