Dynamic simulation of steel lazy wave riser excited at the top-end

Abstract

The use of steel wave lazy risers (SLWR) is increasing for the development of deep-sea oil/ gas production because SLWR reduces maximum tension and touchdown fatigue damage by separating the effect of motion of the platform. Since the static configuration and dynamic response of SLWR are very important for design and fatigue analysis, many numerical and mathematical models are being developed and studied. Because of SLWR with strong geometric non-linearity, there is need the robust and stable method to find the static configuration. The dynamic relaxation method is known to be more stable and more robust than conventional methods with large deflection. Therefore, in this paper, the dynamic relaxation method is developed and applied to estimate the static configuration of the SLWR. The dynamic response of the SLWR using finite element method is estimated from static configuration using dynamic relaxation method. Numerical modeling of riser lines and the dynamic equation of motion are formulated by minimum energy principle. The time-domain solution is obtained by Generalized-α Newmark method. The static configurations of the SLWR are calculated as a result of the variation in the main particulars and the dynamic simulations due to the forced oscillation of the top-end are carried out. The tension of top-end and bending moments of sag and hog points are analyzed through simulation results. And the proposed numerical model is verified through the analysis of OrcaFlex. ？ 2019 by the International Society of Offshore and Polar Engineers (ISOPE).