Research On Hydrodynamic And Energy Characteristics Of Floating Bodies Based On Wave Energy Converter’s Heaving Motion

The energy supply of low-power unmanned marine equipment with long range and long endurance is an importantfoundation of the national deeplysea strategy.It is a nationalstrategic need to absorb,capture and convert ocean wave energy by using wave energy power generation device to provide sustainable,stable and reliable energy.Among many wave energy generation devices,the wave energy generation device based on heave motion is more suitable for the energy supply demand of low-power unmanned marine equipment.During the development of heavy wave energy generation device,the research on hydrodynamic and energy efficiency characteristics of a floating body is the core and key work.In this paper,by means of theoretical analysis,numerical calculation and experimental verification,the scheme design and evaluation of the heave wave energy generation device,the hydrodynamic model and energy efficiency analysis of typical floating bodies,the motion response and hydrodynamic analysis of vertical cylindrical floating bodies,and the energy efficiency matching between two bodies(surface floating bodies and underwater absorbers)are carried out On and experimental research.The main work and innovation of this paper are as following:Combined with the structural characteristics and work requirements of low-power unmanned marine equipment,and integrating the axiomatic design method of mechanical products integrated with TRIZ,four kinds of heave waves are designed to meet the requirements of long range and long endurance of low-power unmanned marine equipment,including axisymmetric revolving body fish-fin type,axisymmetric non rotating body fish fin type,axisymmetric revolving body impeller type and axisymmetric non rotating body impeller type Based on the ideal solution of grey information quantity,the product scheme evaluation method is used to evaluate the above schemes effectively.The results show that the axisymmetric rotor impeller heave wave power generation device is the best scheme to meet the working requirements,followed by the axisymmetric rotating body fish fin type wave energy generation device.To axisymmetric solid of revolution with the rotary body surface floating body and impeller type underwater absorber as the research object,to build the water floating body shape parameters,the wave force,heaving displacement and heaving speed and the constitutive relation between conversion efficiency,using the analytic method to solve the axisymmetric solid of revolution and the rotary body surface of floating body hydrodynamics parameter mathematical model,the key to solve the typical axisymmetric solid of revolution and the plane surface of floating body motion response amplitude operator(RAO),radiation damping,added mass,Froude-Krylov force and conversion efficiency.The results show that under the limitation of space scale of low-power unmanned Marine equipment,the surface floats with the same sea condition,same material and the largest scale axisymmetric rotary body(sphere,vertical cylinder,reverse cone)are more suitable to be used as the surface floats of the impeller type underwater absorber.Based on the study of the energy efficiency characteristics of typical axisymmetric revolving and non-rotating surface floating bodies,this paper further takes the typical axisymmetric revolving floating bodies vertical cylindrical floating bodies(with hemispheres,cylinders and cones as the bottom)as the research objects,and analyzes the floating body shape(spherical,conical,cylindrical),at the bottom of the floating body draft depth and diameter floating body parameters on the influence law of wave energy conversion efficiency.The frequency domain and time domain motion equations and frequency domain analysis models of vertical cylindrical floating bodies are constructed.The influence rules of hydrodynamic parameters on the shape,diameter,draft and wave energy conversion efficiency of the floating body are revealed.The hydrodynamic parameters such as wave force,RAO value,additional mass and radiation damping of various vertical cylindrical floats were calculated by ANSYS-AQWA,and the above parameters were compared and analyzed.The results demonstrate that the vertical cylindrical floating body with a hemispherical bottom,a diameter of 0.3m and a draft of 0.15 m has the highest total wave energy absorption.Based on the motion characteristics of the heave wave energy generation device in the sea area,the energy efficiency matching characteristics between the two bodies(surface floating body and underwater absorber)are studied.The fluid structure dynamic output fluid structure coupling model of the heave type wave energy power generation device in the rising and falling stages is established.It is revealed that under the linear regular wave,different periods of the heave wave energy generation device are different.The influence mechanism of energy conversion efficiency and energy efficiency characteristics of PTO system is discussed.The results show that in the wave period(1.5s,2s,2.5s,3s)selected in the simulation experiment,with the increase of wave period,the energy conversion efficiency of the heave type wave energy generation device and the energy efficiency of the PTO system show a trend of first increase and then decrease.When the wave period increases from 2s to 3s,it decreases with the increase of wave period and reaches the minimum value at 3s;when the wave period increases from 1.5s to 2s,it increases with the increase of wave period and reaches the maximum value at 2s.In order to verify the energy efficiency characteristics of the heave type wave energy generation device,the energy efficiency test platform of the heave type wave energy generation device is built,and the experimental scheme of the energy efficiency characteristics of the heave type wave energy generation device is formulated.The energy efficiency characteristic experiments of typical axisymmetric rotating body and non-rotating type water surface floating body,various vertical cylinder type surface floating body energy efficiency characteristics experiment and heave type water surface floating body are carried out respectively.The relationship between wave period,shape of floating body,diameter of floating body,draft depth and energy efficiency characteristics is tested.The results of theoretical analysis and numerical calculation are verified effectively.