Analysis Of Relative Motion Of SPAR And Semi-submersible Floating In Waves

The process of construction, transportation and installation of SPAR platform is a huge project. After SPAR construction, it need to be transported to the designated place to offload. During its offloading, with the semi-sub sinking, the SPAR gradually goes into a floating state, waiting for the tugs to separate it from the semi-submersible. At this time with the SPAR and semi-submersible close to each other, collisions may extremely easily take place with the influence of the external environment, such as waves.This subject is based on the above problems to do some researches about SPAR and semi-submersible relative motion in waves, which will provide reasonable advice for SPAR offloading work, as well as other large structures. For this topic, at present the research is still blank inland. Overall, this project can be classified to the research about hydrodynamic interaction between multi-body structures.In this paper, the 3D potential theory is as a guide which is used widely inland and abroad to do hydrodynamic calculation, and introduction about research and application of this theory in multi-bodies calculation is also given gradually. The AQWA software is used to model and simulate the SPAR platform and semi-sub offloading process. First in this paper, typical models are tested by using AQWA software which gives exact results compared with the data given in literature; Then, SPAR platform and semi-submersible are modeled and imported into AQWA software to do hydrodynamic calculation; With the method of frequency domain, short-term prediction of SPAR and semi-submersible collision probability is given and a new time domain method which is based on the collision force is introduced to calculate the motion of the two floating structures, statistic analysis is also done; Finally, factors that may affect the relative motion of the SPAR offloading are discussed, such as the distance between the SPAR and the semi-sub, wave propagation direction and water depth, which will provide reasonable basis for the offloading work.