Abstract:[Purpose] The flapping foil, as a simplified model for energy extraction studies, converts tidal energy into electrical output. While its behavior under uniform flow is well-studied, complex flow conditions with unsteady vortices require further investigation of NACA0015 airfoil under cylinder wake effects. [Methods] Using CFD simulations, this study examines hydrodynamic characteristics and energy harvesting efficiency under various motion parameters, analyzing vortex structures and the effects of pitching and heaving amplitudes. [Results] Energy capture efficiency increases with heaving amplitude, while cylinder wake effects decrease with larger pitching amplitude. [Conclusion] The analysis provides a reference scheme for efficient tidal energy collection in offshore wind farms, contributing to both improved efficiency and reduced tower vortex-induced vibrations.