Study Of Chordwise Flexibility On The Tidal Current Energy Extraction Performance Of An Oscillating Hydrofoil

The tidal energy turbines have many advantages which include low flow velocity,low underwater layout height,high energy extraction efficiency,and harmless effects to marine animals.At present,the research on tidal current energy extraction technology with oscillating hydrofoil is mostly concentrated on the rigid hydrofoil.There are few studies on the influence of the hydrofoil chord-wise deformation on the energy extraction performance.In order to improve the energy extraction performance,this project tries to explore the energy extraction performance for chord-wise flexible hydrofoil.The main aspects studied are as follows:(1)Based on the comprehensive research status analysis of oscillating hydrofoil energy extraction device at home and abroad,the movement characteristics and energy extraction principle are analyzed and the energy extraction performance improvement scheme is determined.The knowledge of bionics is used to establish the control model of chord-wise flexible hydrofoil.According to the control model and the analysis results of the rigid hydrofoil,the movement characteristics and energy extraction principle of the flexible oscillating hydrofoil are determined.(2)Partial parameters of the chord-wise flexible hydrofoil are determined by the knowledge of rigid hydrofoil.According to the control model of the flexible hydrofoil and the related research results of flexible bionic propulsion,the deformation control equation of the hydrofoil and the deformation parameters are derived.A two-dimensional oscillating hydrofoil motion model is established by using the pre-processing software Gambit to mesh the fluid domains,and the rationality verification of the model is also completed.Preliminary screening the pitch motion amplitude of chord-wise flexible hydrofoil based on the basic motion parameters.(3)In order to study the impact mechanism of chord-wise flexure on the tidal current energy extraction performance and the hydrofoil surface attached vortex,the relationship between the hydrofoil surface attached vortex and the pressure on the hydrofoil surface,the relationship between the hydrofoil surface attached vortex and the hydrofoil lift,and the relationship between the hydrofoil lift and the hydrofoil energy extraction performance are studied in this paper,and the interaction between the hydrofoil surface attached vortex and the energy extraction power is obtain.The variation of hydrofoil surface attached vortex is represented by the quantification of the vortex,revealing the effect of the chord-wise flexure on the attachment vortex.(4)Based on the study of the rigid hydrofoil,further research on the optimal parameters of the chord-wise flexible hydrofoil is carried out.The numerical analysis of hydrodynamic parameters at different reduced frequencies,chord-wise flexure,pitching motion amplitude and hydrofoil shapes are performed.By explored the effect of these hydrodynamic parameters on energy extraction of flexible hydrofoil,the relations and features of energy extraction performation to hydrodynamic parameters are summarized.According to the analysis results,the optimal hydrofoil shape and pitching motion amplitude are obtained.