Coupled Analysis and Assessment of a Surface Buoy and Umbilical System in Irregular Waves

A coupled 3-D finite element model of a buoy system including a surface buoy, an umbilical and a riser was developed to study the system’s global dynamic responses in sea states (irregular waves and currents) using commercially available software (such as WAMIT, RIMO, RIFLEX). The model is used for verification of the design of the system and determination/assessment of the limiting sea states based on the system’s performance and the design criteria. The limiting sea states are the sea states on a boundary curve of a sea state range (domain) within which all the system design criteria are met. The design criteria include the maximum tension, maximum compression and minimum bend radius for the umbilical, and the maximum tension, minimum bend radius and maximum angle relative to the axis of the bellmouth for the riser. The method has been used successfully for the verification of the design of a buoy system and the assessment of its global performance. It is confirmed that the design meets the project’s expectations and the system is fit-for-service.