COUPLED DYNAMICS OF SPARS IN DEEPWATER

摘要

This paper presents a discussion of the effect of including mooring line dynamics and riserrnreactions on Spar response in different water depths. Coupled analysis capability was used tornpredict the Spar motions. Previous studies show that modeling of risers and mooring linesrnimproves motion prediction when compared to full-scale data [1]. The relative importance ofrnthese additional effects for different water depths is evaluated. Since the heave motion is reducedrndue to increased damping, a shorter draft classic Spar configuration is analyzed to demonstraternfeasibility of the concept.rnResults obtained demonstrate that the heave motion of the Spar is greatly reduced when risers andrnmooring lines are included in the analysis. Pitch response is also reduced due to inclusion ofrnmooring lines and risers. The effect of the coupled analysis also is to reduce the mooring linerndynamic tensions. In addition, riser fatigue damage resulting from friction-induced axial stressesrnis predicted to reduce from those obtained using an uncoupled analysis. The effect of thernadditional damping on Spar response to long period waves is also presented. The lessrnconservative predictions of heave motion presented herein make it possible to reduce Spar hullrndraft, which will reduce hull fabrication and transportation costs.