Prediction of deepwater riser VIV with an improved time domain model including non-linear structural behavior

Abstract

In this paper, vortex-induced vibrations (VIV) of deepwater risers including the VIV-induced tension fluctuations were simulated using a time domain VIV model. Data from a large-scale riser experiment was applied for correlation studies. As a first step, a new combination of in-line and cross-flow synchronization models with empirical parameters was proposed for better in-line response prediction. The performance of the improved load model was investigated based on a linear riser model. The results showed that the in-line response and its synchronization pattern were improved compared to the previous load model. Then, the improved load model was combined with a non-linear structural riser model to explore the effect of tension fluctuations. As observed in the tests, simulations showed that the tension fluctuations influenced the stability of VIV and possibly decreased the resulting vibration amplitudes. Lastly, the VIV prediction performance of the load model was evaluated with respect to frequency contents, stress levels, and fatigue damage. From the results, it was found that the improved load model in combination with the non-linear structural model reflected the response characteristics observed in the tests.