A nonlinear model for deepwater steel lazy-wave riser configuration with ocean current and internal flow

Steel lazy-wave riser (SLWR) has gained a viable solution as a kind of advanced steel catenary riser (SCR) to meet the increasing challenges of simple catenary riser on large hang-off tension and fatigue damage of touchdown point (TDP) in deepwater applications. The configuration and static performance of SLWR are essential during its design stage and varies a lot when subjected to loading from ocean current and internal flow. The governing equations which consist of conventional small deformation beam theory for the portion of pipeline lying on the seabed, coupled with a large deformation beam theory for the suspended section are established. The proposed model with appropriate boundary conditions can simulate the nonlinear mechanical behavior of SLWR with the effect of pipe-soil interaction, ocean current and internal flow. The finite difference method is adopted to obtain the numerical results, and comprehensive parametric analysis is carried out to investigate the influences of ocean current and internal flow on the riser's static performance. The proposed model can be an important reference for the design and analysis of deepwater SLWR.