Hydrodynamic Analysis Of The Oscillating Hydrofoil In Tidal Energy Extraction Devices

The energy crisis and environmental pollution problems in the contemporary society are intensifying,and the competition for mining of the huge energy treasures between the countries is becoming increasingly fierce.As a clean renewable energy source,tidal energy is not only abundant in the ocean,but also easy to obtain.The energy density is high,and the predictability is very strong.More and more countries are developing a large number of power generation equipment s.With the rapid development of China's maritime powers,the development and utilization of more sophisticated marine projects have gradually attracted the attention of the states and enterprises.China will also provide sustainable development for the national society through the comprehensive utilization of marine energy.This topic is based on the application of oscillating hydrofoil technology in the capture of tidal energy for power generation and the hydrodynamic performance of the hydrofoil system.Like the process of fish tailing,the oscillating hydrofoil technology is actually the combined motion of the heave motion and the pitching motion around the axis of rotation.It can be used not only to slap the water body for bionic propulsion.Under the action of tide,the periodic reciprocating motion of the oscillating hydrofoils can be performed,and the tidal current energy captured by the hydrofoils can be transmitted to the generator through the mechanical mechanism,then converted into electric energy.In this paper,the effects of various parameters on the energy capture efficiency of the hydrofoil technology are analyzed,including the frequency of the hydrofoil oscillation,the amplitude of the pitch angle,and the amp litude of the submerged motion as well as the geometrical parameters of the hydrofoil which include chord length,and pitching axis position.The influence of the spacing of the upper and lower parallel symmetrical oscillating hydrofoil arrangements on the system is explored,in order to make each hydrofoil to achieve the highest energy capture efficiency.Tt is finally found that the oscillating hydrofoil placed parallel ly to the top and bottom,when the initial spacing is small enough,will creat a dynamic "wing-ground effect" between each other,greatly improving the hydrofoil lift-drag ratio and the hydrodynamic properties of the system.By studying the influence of many parameters on the hydrodynamic characteristics of the hydrofoil system and using the CFD method to simulate the application scenario of the two-stage hydrofoil series arrangement,the irrationality of its spatial layout is found.The efficiency is low.The oscillation is disturbed and the system stability is poor.Simulation and analysis were carried out for the problem that the contribution of the “wing-ground effect” to improve the energy efficiency of hydrofoil capture is not obvious,and the reasons and further improvement ideas were found,the use of the collecting plate and optimization of the hydrofoil motion control equation,which made a foundation for the subsequent research of this topic.In the simulation technology,the computational fluid dynamics soft ware ANSYS Fluent is used to calculate the hydrodynamics.The overlapping mesh technique is used to process the boundary motion,which ensures the high mesh quality in the whole process,avoiding many problems in the traditional dynamic mesh such as mesh regeneration and deformation.And the paper is verified by comparing with the published literature.The simulation obtained a good flow field change process,and obtained a series of pressure cloud maps and vorticity maps.