HYDRODYNAMICS OF DISCONNECTABLE TURRET SYSTEMS - background
In recent years there have been a growing number of projects in the offshore industry that use disconnectable turret systems. The advantage of such a system is that in case a large hurricane or typhoon is moving towards the FPSO it can be disconnected from its risers and mooring quickly to avoid any damage to the facility. In this disconnection phase the turret buoy is detached from the vessel and drops to a safe depth of 100-200m below the surface. The FPSO is then moved to a safe area until the storm has passed by. Afterwards the buoy can be picked up again and reconnected to the FPSO in a short period of time.
In recent years we have learnt that it is challenging to predict the buoy behaviour during disconnect and reconnect without performing extensive model tests at multiple scales. The present JIP proposal focuses on the hydrodynamic design aspects of the buoy in disconnection phase and aims to deliver tools to predict the behaviour in the design phase of the project.
The aim of this JIP is to better understand the hydrodynamics of a disconnected turret buoy in close proximity of the FPSO in high sea states. The final objective is to predict dropping behaviour and the motions and mooring forces on the buoy during the disconnection phase in a given wave and current. Model tests and CFD will be used to predict the buoy behaviour and interaction with the moving FPSO in waves and current. The initial acceleration and final velocity of the dropping buoy will be tested and predicted using CFD and a time domain simulation tool for various buoy shapes.