Abstract
To improve the energy extraction performance of the oscillating hydrofoil, the lift force that acts on the oscillating hydrofoil is analyzed. The pressure difference between the oscillating hydrofoil‘s opposing surfaces is dominant to generate the lift force. Forming and shedding of the leading-edge vortex from the hydrofoil surface determines the pressure difference between the opposing surfaces of the oscillating hydrofoil. In this paper, the hydrofoil with different chord flexibility coefficients and maximum offset at the trailing edge are analyzed to obtain the power coefficient, lift coefficient, and moment coefficient of the oscillating hydrofoil. The influence mechanism of chord-wise deformation of the oscillating hydrofoil on the energy extraction performance is explored. According to the Kutta–Joukowsky condition and the Stokes’ theorem, the relationship between the attached vortex on the hydrofoil and the surface pressure of the hydrofoil, the surface pressure difference of the hydrofoil, and the lift force that acts on the hydrofoil are investigated. By quantifying the vortex intensity, the ascending-shedding process of the attached vortex on the hydrofoil is characterized. Finally, the complete influence chain among the chord-wise flexure, the attached vortex on the hydrofoil, and the energy extraction performance of the oscillating hydrofoil is established.
Highlights
As an important form of ocean energy, tidal current has the advantages of large reserves, high-energy flow density, and being eco-friendly
According to the Kutta–Joukowsky theory, in inviscid flow, the lift force that acts on the hydrofoil is dirTehctilsy spercotpioonrtimonaainlltyo tshtuedvioesrtetxhecirecfufelcattsionof, ahnyddtrhoeforiellacthioonrdsh-wipisies edxepforersmseadtioinn Eoqnuahtyiodnro(1fo8i)l, attachment leading-edge vortex, hydrofoil surface pressure distribution, and lift force, so as to find how they affect the energy extraction performance
The energy extraction performance of the oscillating hydrofoil with chord-wise flexibility was analyzed by quantifying the vortex that is attached to the hydrofoil surface
Summary
As an important form of ocean energy, tidal current has the advantages of large reserves, high-energy flow density, and being eco-friendly. For the effect of the geometric parameters on the energy extraction performance, Lindsey et al concluded that reducing the foil thickness can improve the hydrofoil energy extraction performance, and Usoh et al found that the rectangular cross-section foil is more efficient than National Advisory Committee for Aeronautics (NACA) foil [11,12] It is well-recognized that the lift force acting on the hydrofoil is caused by the pressure difference between the up and down hydrofoil surface; whereas, the pressure difference is caused by the attached vortex that is forming and shedding from the surface of the hydrofoil. Studies about the flexible foil performed by Hoke et al and Wu et al have conclusions in the laminar flow environment (Reynolds number Re = 1100), and Liu et al carried out numerical simulations in the turbulent flow environment (Re = 100,000) They only explored the feasibility of improving the hydrofoil energy extraction efficiency by flexible deformation numerically. The vortex that attached to the hydrofoil’s surface is quantified, and the distribution of the pressure coefficient along the hydrofoil’s surface is analyzed in detail to better reveal the effect of the chord-wise flexure on the energy extraction performance
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
