DEVELOPMENT OF PREDICTION METHOD FOR BEHAVIOR OF TOTAL SYSTEM INCLUDING FLOATING BODY-RISER-MOORING LINE INTERACTION

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In order to investigate the behavior of a moored floating body with flexible riser pipes under natural environment conditions such as wave, wind and current, it is necessary to take account of interaction among a floating body, mooring lines and riser pipes. This interaction reveals nonlinearity which means that responses of motions of afloating body internal forces of riser pipes and tension of mooring lines are all non Gaussian even though wave, wind and current are Gaussian. Therefore in order to predict extreme values of above mentioned responses, we have to develop the computer code in time domain which should be validated by the corresponding experiments.At first , the authors developed the computer code for nonlinear dynamics of moored floating structure with flexible riser pipes in time domain which take into account the interaction between a moored floating body and riser pipes.Secondly they completed the CFD code for hydrodynamics on 2D circular section in separated oscillating flow in time domain.Thirdly they developed the computer code for riser pipe dynamics which is connected with the CFD code.At last, with regard to the validation for the above mentioned computer codes, they developed the optical apparatus for measuring 3D behavior of flexible riser pipes. They wade clear the characteristics of the chaotic phenomena of the behavior of the bottom end of the flexible riser pipes.Finally they established the practical analysis method for dynamics of a floating body and riser pipes which consider interaction effect between a floating body and riser pipes, and also which take account of only the drag force on a riser pipe section in which Keulegan carpenter number varies. However the computation diverges when not only drag force, but also lift force are considered at the some time. This subject is the important one solved in future.