HYDRODYNAMIC PERFORMANCE EFFECT OF STEEL CATENARY RISERS ON WAVE FREQUENCY MOTIONS OF A SEMI SUBMERSIBLE

摘要

The analysis of the influence of risers on the motions of a floating platform is often conducted and simplified by uncoupled method. As the number of risers and water depth increase, this method would not predict system motion accurately. Coupled analysis method in time domain becomes a very convenient approach in response calculation since it automatically includes the interaction among platform, mooring lines and risers. This paper introduces a full coupled approach by AQWA-NAUT to include viscous damping of the semi submersible and effects of steel catenary risers on the wave frequency response of platform in time domain motion analysis. The main conclusion of this paper is that full coupled method can accruately predict semi submersible Response Amplitude Operator (RAOs) comparing to the case without risers. Other conclusions are that risers have an important effect on the wave frequency motion of semi submersible and also lead to a phase lag with respect to platform motions.