Alternative design of flexible jumpers for deepwater hybrid riser configurations

Recent studies on the behavior of the simple free-hanging configuration for flexible risers have shown that, for very deepwater levels, they are reach ing their technical and economic limits. Other alternative configurations a re currently being investigated, including hybrid riser configurations base d on flexible jumpers connected to an intermediate point closer to the free surface (usually a submerged buoy). This work focuses on the jumper issue, considering that, since it is completely suspended, its behavior may diffe r significantly from the behavior of a riser resting on the seabed Therefor e, the usual design procedure employed for conventional applications may no t be completely adequate, and should be complemented by alternative approac hes. This work considers analytical, numerical, and experimental approaches for the design of flexible jumpers. First, a comprehensive static analysis using consistent catenary concepts is developed this results in criteria t hat are essential for safe design. Subsequently, a modal analysis procedure is described; this procedure considers the nonlinear behavior of the jumpe rs under the static component of the environmental loads, and may show the existence of resonant modes that require careful consideration. This define s the importance of damping mechanisms, and orients parametric time-domain nonlinear verifications. Finally reduced model tests are considered devised specifically to investigate the jumper behavior under centenary conditions . The design of the physical model and the similarity analysis of the exper imental results are also presented.