Impact of Spanwise Deformation on the Hydrodynamic Performance of an Oscillating Hydrofoil

Aiming at the problem of spanwise deformation during the operation of oscillating hydrofoils, this study adopts the computational fluid dynamics (CFD) method. Based on the k-ω turbulence model under the simulation condition of Reynolds number N_Re=150 000, a user-defined function (UDF) is utilized to control the spanwise deformation, so as to investigate the influence of different spanwise deformation degrees on the hydrodynamic performance of the oscillating hydrofoil with a twin-support configuration. By actively controlling the spanwise deformation of the hydrofoil and combining different deformation coefficients, the flow field simulation of the oscillating hydrofoil and the calculation of hydrodynamic coefficients are carried out, and the evolution laws of the pressure distribution on the hydrofoil surface and the vortex shedding characteristics are analyzed simultaneously. The computational results indicate that: spanwise deformation affects the shedding of spanwise vortices on the pressure side and the formation of vortices on the suction side of the oscillating hydrofoil, thereby altering the pressure distribution along the spanwise direction of the hydrofoil; compared with the rigid hydrofoil (α=0), the energy extraction efficiency of the oscillating hydrofoil with spanwise deformation decreases by 2% to 5.8%, and the efficiency reduction amplitude increases with the increase of the deformation coefficient α. When α=1.5, the system power coefficient decreases by 5.4% compared with that of the rigid hydrofoil, indicating that the spanwise deformation degree exhibits a significant negative correlation with the energy capture performance. In engineering applications, methods such as material selection should be adopted to suppress the spanwise deformation of the hydrofoil, thereby achieving the optimal overall performance of the device.