Nonlinear Dynamic Analysis of Deepwater Steel Lazy Wave Riser Subjected to Imposed Top-End Excitations

As an effective solution for deepwater oil/gas export, steel lazy wave riser (SLWR) could effectively accommodate large platform offsets, decouple platform motions from the touchdown point and reduce top tension in deepwater marine environment. Since the SLWR dynamic response is very essential for design phase and fatigue analysis, it has already drawn extensive research attention. This paper puts forward a developed mathematical model on the basis of the rod theory and finite element method to predict the static/dynamic response of deepwater lazy wave riser. Newmark-β method combined with Newton–Raphson iterative method is employed for time domain integration of the riser dynamics. Besides, the effects of hydrodynamic loading and internal flow are considered in the mathematical model. The verification of the propose model can be well demonstrated by comparing with OrcaFlex simulation. Finally, parametric analyses about the buoyancy segment are conducted to study the SLWR dynamic response in the critical zones, like the hang-off point and touchdown zone (TDZ).