Numerical Evaluation of Fatigue Damage of the Deepwater Riser Induced by VIV Using Pseudo-Excitation Method

The fatigue damage of a long flexible riser undergoing vortex-induced vibration (VIV) in deepwater is numerically studied using pseudo-excitation method (PEM) in present paper. For evaluating the fluid-structure interaction problem of vortex-induced vibration of bluff bodies at high Reynolds number, the strip theory approach is taken into consideration, and the discrete vortex method (DVM) is used to calculate the vortex-induced vibration of each strip to obtain the load spectrum for the calculation of pseudo-excitation, while the finite volume method (FVM) is employed for evaluating the structure dynamics of a long flexible riser. The DVM model is validated by its comparison with the experimental results. The vortex-induced vibration is considered as a stationary random process. The response of riser to vortex induced excitation is calculated using pseudo-excitation method (PEM). The fatigue damage rate of the riser per year is evaluated and the service life of the riser can be predicted based on the Palmgren-Miner Rule.