Investigation On The Hydrodynamic Characteristics Of Round-shaped FPSO Induced By Freak Wave

Using the method of physical model test,the hydrodynamic characteristics of the round-shaped FPSO were studied by means of irregular wave and freak wave.The influence of the mooring mode,relative wave height,relative period and freak wave parameters α1~α4 on motions and mooring force of the round-shaped FPSO is discussed.The results of the test show:The motion response and mooring force of the floating body are significantly related to the wave parameter α1,which are not significantly related to the freak wave parameters α2 ~α4.In the same spectrum,the freak wave can produce larger motion and mooring force than irregular wave.In the test range,floating body’s sway,heave,roll motion and the seaward,leeward mooring force under the action of freak wave can reach 1.6 times,2.2 times,1.8 times,1.9 times and 2.5 times respectively of those under the action of irregular wave.Therefore,it is necessary to consider the influence of freak wave on mooring floating bodies in the presence of freak wave.In the up four point mooring mode and up three point mooring mode,body’s sway and heave motion is small,in the up four point mooring mode,the mooring force is the least.Mooring point located in the height of gravity center can better limit the linear displacement of floating body.Whether freak wave is included in the irregular wave series or not,sway,roll motion and mooring force of floating body always show their low frequency characteristics,whose period can reach more than 20 times of the wave period.Frequency range of heave motion and the frequency range of irregular wave series is relatively close,by changing the heave natural frequency of floating body can make it far from conventional irregular wave frequency range.