Research On Hydrodynamic Response Of Soft Yoke Moored Ship Based On AQWA

With the deepening of the development of marine resources,all kinds of marine operating platform have been put into use.At present,almost all of China's offshore production platform are powered through the self-built generator sets.There are many deficiencies of this approach,So there is consideration using a dedicated floating platform to provide energy,and single-point soft yoke for mooring system.Since the ship with the soft yoke moored usually has large motion,to study the safety of the ship at sea,this paper studies the hydrodynamic response of the offshore platform with soft yoke mooring system based on AQWA software,and analyzes its law of motion and mooring force in marine environment load.In this paper,the numerical calculation of floating platform frequency domain is carried out,and the hydrodynamic parameters such as motion amplitude response operator,first order wave force,additional mass and radiation damping are obtained.Motion behavior is discussed in different water depth,draft and wave direction.And then the Multi-rigid body coupling dynamic analysis model of the floating platform with soft yoke mooring system is established.The time-domain simulation of the mooring ship is carried out in irregular wave and combined loads of wind,wave and current.The time-domain simulation of the response of motion and mooring load is carried out with different combinations of wind,wave and current.Here is mainly conclusion:(1)The motion RAOs in the horizontal plane decreases rapidly with frequency increased and the effect of water depth on RAOs is not obvious.In the frequency range and high frequency range,the RAOs in vertical plane decrease with the water depth reduced.(2)With the decrease of water draft ratio,the additional mass and radiation damping have increased significantly,especially in the vertical plane,and the increasing trend is obvious.(3)Under the condition of wind wave and current,the ship of the equilibrium position depends mainly on the directions of wind and current,flow direction,and it has little relation with the direction of wave.(4)Under the condition of head wind and head wave,the amplitudes of ship movements increase with the angle between the current load and the initial bow of the ship.In the condition of head wind and oblique wave,the amplitude of ship movement increases with the angle,especially lateral motion(sway,roll,yaw).In the condition of head wind,head wave and cross current,and head wind,oblique wave,no current or oblique current,the mooring ship gets the maximum motion responses and the mooring force reached maximum.These can be considered as most dangerous combination of loads.(5)In the sea loads of one-in-1000-year and one-in-10000-year,motion in X-Z plane(surge,heave and pitch)increased sharply.Violent collision of soft yoke and ship happens,producing the maxima mooring force far exceeds the design value.(6)The increased motion and mooring force response of the ship caused by the increase of the draught not obvious.(7)As the water depth decreases,the motion response in horizontal plane increases considerably,and the vertical motion decreases significantly.Corresponding,the mooring force in X direction increases,mooring force of mooring leg in Z direction decreases.(8)In the sea loads of one-in-10000-year,the motion response decreases little with the increasing of the water quality of soft yoke,but the mooring force of soft yoke will increase significantly.