Analysis Of Multi-body Responses In FPSO Tandem Offloading Operation

Offloading system is an important part of the whole FPSO concept. FPSO offloading operations are likely to be affected by many factors, such as the rigorous and changing sea conditions, hydrodynamic interaction between FPSO and shuttle tanker and relative motions between the two vessels. In this paper, systematic evaluations of hydrodynamics and responses of multi-body system in FPSO tandem offloading operation with a shuttle tanker which is connected by a hawser are performed. The main contents of this paper include:Analyses of hydrodynamic performance of multi-body, which consist of a FPSO in tandem configuration with a tanker in the South China Sea, are applied in three typical loading cases and three groups of distances between the two vessels. Taking into account for the hydrodynamic interactions, the first order wave force, first order motions RAO and second order wave force of each vessel are calculated. Comparative study is performed to analyze effects of the different parameters.Time-domain simulation analyses of multi-body system in offloading operation are performed in this paper. The responses of multi-body system in different loading cases, different parameters (length and EA) of offloading hawser, action of tug and wicked environmental conditions (changing wind speed and direction) are calculated concerning the problems of relative motions of the two vessels and intensity of hawser. Curves of relative motions and tensions in the hawser are obtained from the analyses. The effects of different loading cases and different parameters of multi-body system are assessed by the comparative study.