Numerical Simulation On Hydrodynamic Response Of Wave Action On Mooring System

The motions of some moored ocean structures, such as ships ,buoys, floating breakwater ,and semi-submerge flat roof under wave forces affects structure and working stability ,so it is important to study the hydrodynamic response of mooring system. In this paper, the motion of buoy is obtained numerically using a high-order boundary element method in the time domain based on the linear 3-D potential theory. The ultimate conclusions from the research provide theoretical basis and project reference.In this paper, The numerical method is adopted to calculate the motions in time domain based on the simple Green function and perturbation expansion method put forward by Isaacson and Cheung. The mooring force on buoy is calculated in use of the catenary's theory and B-Spline functions fitting, then the motion equation is solved in time domain.First of all, the response and force on a fixed cylinder in open sea can be solved using the numerical program in time domain, the result fits in with the frequency value well.Secondly, the cylinder motion of linearly restricted system is calculated under wave exciting-force .Stiffness of the spring system is considered into frequency calculation in order to compute the system's motion. The two results don't agree with each other very well because of the inherent mode of the system, adding proper damp the good agreement examines the numerical method.Thirdly, geometry and mechanics equation on arbitrary point of the mooring line is deduced based on the catenary's theory . By using B-Spline functions the relationship curve between excursion and mooring force can be obtained, so the mooring force on buoy during the motion is known.Finally, influence about the motion varying with the some situation factor is discussed using the numerical. Analyzing the result some useful conclusion can be drawed and direct the engineering.