Research On Hydrodynamic Characteristics Of Flap-type Oscillating Hydrofoil Tidal Current Energy Generation Device

Ocean energy is a kind of non-polluting renewable energy with huge reserves,which has received extensive attention from the international community.According to the survey,the theoretical reserves of global marine energy are as high as 766,000GW,which has a very broad development prospect There are many types of ocean energy,mainly including offshore wind energy,tidal energy,tidal energy,temperature difference energy,salt difference energy,etc.,of which tidal energy is an important part.At present,tidal energy has become a very active branch in the field of marine energy development technology,and new marine renewable equipment has also been rapidly developed.As a kind of tidal current energy generation device,oscillating hydrofoil has obvious advantages in shallow sea,and its power generation efficiency is comparable to that of traditional tidal turbines with rotating blades.Its working principle is that the underwater wing generates oscillating motion under the action of the power flow,and the oscillating motion is converted into rotational motion through the hydraulic device,and then the generator is driven to generate electricity.Existing conventional oscillating hydrofoils mostly use rigid integral airfoils,which are simple and reliable in structure,but have low adjustable performance and unsatisfactory power generation.Based on the existing conventional oscillating hydrofoils,this paper proposes a flap-type oscillating hydrofoil structure with flaps.The structure is to add trailing edge flaps at the rear end of conventional hydrofoils,and use the swing of the trailing edge flaps to achieve the purpose of increasing power.In this paper,three flap-type oscillating hydrofoil models are established with reference to the existing aviation and navigation literature,including simple flap-type,Gurney flap-type,and Fowler-flapper-type.In this study,a theoretical model of flap-type oscillating hydrofoil was proposed and established based on the Jukovsky lift formula,and the equivalent angle of attack equation of the oscillating hydrofoil was deduced.This theoretical model can effectively verify the flap-type oscillating hydrofoil theoretical results.Numerical simulation models of simple flap type,Gurney flap type and Fowler flap type are established by Fluent software,UDF programming is performed on the motion of the hydrofoil model in CFD software,and the motion parameters of the hydrofoil are controlled by the UDF program.,studied the flap length,flap amplitude,flap motion period,as well as the Fowler motion,slot value,overlap and other parameters in the Fowler-type flap,and analyzed the changes of these parameters on the lift of the oscillating hydrofoil coefficient,drag coefficient,and the influence of energy harvesting efficiency,the optimal structural forms of the three flap-type oscillating hydrofoils are obtained.The coefficient efficiency reaches 60%,which is 85%higher than that of conventional oscillating hydrofoils.In this paper,an experimental platform of the towed trolley pool is built,and the changes of the lift and drag of the oscillating hydrofoil caused by the motion parameters of the oscillating hydrofoil in the pool are studied;the motion parameters of the main wing and the flap of the simple flap-type oscillating hydrofoil are studied;A series of hydrodynamic parameters such as lift coefficient and drag coefficient of conventional hydrofoil and simple flap type oscillating hydrofoil were compared;the theoretical structure and numerical simulation conclusion of simple flap type oscillating hydrofoil were verified,and the simple flap oscillation was proved Structural rationality of hydrofoils.It is believed that the trailing edge flap structure increases the camber of the oscillating hydrofoil airfoil,which increases the angle of attack of the oscillating hydrofoil,thereby increasing the lift coefficient and time-average power coefficient of the oscillating hydrofoil.The derived equivalent angle of attack formula is consistent with the simulation results,and the equivalent angle of attack formula can better predict the simulation results.The negative swing work of the trailing edge flap accounts for a small proportion of the power collected by the entire oscillating hydrofoil,about 2.2%.According to the existing sea conditions in my country,and referring to the existing design standards and materials of the rudder,the conventional oscillating hydrofoil and the simple flap-type oscillating hydrofoil are designed.The data of the fluid simulation is loaded into the stress analysis module,and the structural stress characteristics of the hydrofoil under normal and abnormal operating conditions are analyzed.The results show that the maximum deformation of the hydrofoil is elongated,and the maximum equivalent stress is 336MPa.The results show that the hydrofoil material and structural design can meet the requirements of sea conditions.The existing relevant design standards and the results of the fluid-structure interaction simulation are mutually supported and verified,and the design method of the oscillating hydrofoil and the relevant reference design standards are explored and proposed.This topic proposes a novel structure of flap oscillating hydrofoil,enriches the research theory of oscillating hydrofoil,improves the types of tidal energy power generation devices,and provides relevant reference content for the development and development of marine energy in our country.