Hydrodynamic Performance Analysis And Dynamic Characteristics Research Of Mooring System For Oscillating Buoy Wave Power Device

With the continuous consuming of global resources,the reserves of fossil energy decreases gradually,stimulating the development of new energy technology.Wave energy,as a new renewable energy,is beginning to be taken seriously in recent years.Various types of wave power generation devices in different countries around the world are endless,including oscillating water column(OWC)wave power device,oscillating buoy wave power device,contraction channel wave power generation device and raft-type wave energy converter.The structure in this paper is divided into three parts:buoy,which is equivalent to the mover,can move with the wave motion to capture wave energy.The motion spectrum will best approximate the wave frequency.The main floating body,which is equivalent to the stator,carries the power generation system of the wave energy converter.The motion spectrum will best avoid the wave frequency;mooring system on the wave energy converter can fix the device in extreme sea conditions to ensure the survival performance of wave power generation device.In this paper,the dynamic characteristics and the motion performance of the main float stability and the effectiveness of the mooring system under extreme sea conditions are analyzed.In the first,the principle and classification of wave energy generating devices are systematically introduced,and several typical wave power generators are described in detail.In view of the positioning and safety of floating bodies in the ocean,the mooring system of marine structures and wave energy generating devices is introduced,and the differences between wave energy generating devices and other offshore platforms are listed.The theory of hydrodynamic analysis of marine structures is introduced,including basic equations,boundary conditions and hydrodynamic coefficients,providing the basis for the following time domain analysis.Secondly,the main float of the wave energy converter is simplified and modeled in ANSYS-APDL.The model is imported into AQWA-LINE to study the hydrodynamic characteristics of the main float in the frequency domain analysis.The RAOS,additional mass,additional damping,first-order wave force and second-order wave force of the main float in different frequency and wave directions are obtained.Then,the time-domain analysis of the main floating body and the mooring system under different sea conditions is carried out by using the hydrodynamic parameters obtained in AQWA-LINE.The influence of mooring system on the motion characteristics of the main floating body under the operating sea conditions.And the influence of different anchor chain diameter,mooring point coordinates and mooring scheme on the motion characteristics of the main floating body is studied under extreme sea conditions,and the original scheme is optimized.The analysis of mooring parameters shows that the larger the diameter of the anchor chain,the larger the mooring radius and the smaller the amplitude of the main floating body.The influence of mooring radius on the swing is not obvious,but the larger the diameter of the chain is,the greater the pitch is.The use of four chains cannot improve the mooring system performance.The feasibility of the optimization scheme is verified by the simulated the tension of the mooring cable and the length of the laying chain.Finally,in the time domain analysis,the mooring system simulates the influence of an anchor chain on the main floating body.Simulation results show that the optimized scheme and the damaged mooring system meet the safety requirement.Finally,the frequency and time domain analysis of the main float structure of the wave energy converter are studied.The effects of different center of gravity position,different heave plate shape and opening holes scheme on the dynamic characteristics and motion performance of the main float are studied.The results show that the position of the center of gravity has no effect on the heave motion of the main float,but the higher the center of gravity,the greater the natural period of pitch.The shape of the heave plate will affect the heave and the roll of the RAO peak of main floating body,without affecting the natural period.Heave plate with holes will reduce slightly natural period.The different ways of opening holes on heave plate will increase the pitch amplitude.Heave plate with damping holes can improve the hydrodynamic performance of the main floating body,reduce the main floating body heaving and change the main floating body natural period.