Tandem hydrofoils can achieve high energy-harvesting performance due to the shared flow window and positive interaction between the fore and hind hydrofoils. However, the wake effects generated by the fore hydrofoil (FH) can prevent the hind hydrofoil (HH) from achieving optimal energy-harvesting performance. To address this limitation, the concept of tandem hydrofoils with different fore and hind hydrofoil parameters is proposed. Using the single hydrofoil (SH) and tandem hydrofoil with identical parameters (THIP) as benchmark, the energy-harvesting performance of tandem hydrofoils with different parameters (THDP) is investigated through a three-dimensional (3D) numerical study. This study explores the effects of damping coefficients, pitching amplitudes, and reduced frequencies on the energy-harvesting performance of THDP. Due to the blocking and disturbance effects of FH on the flow, the wake velocity decreases, resulting in a significant drop in the energy-harvesting performance of HH in THIP. Consequently, the maximum overall efficiency and power coefficient of THIP are 0.332 and 0.543, respectively. Compared to THIP, HH in THDP demonstrates superior energy-harvesting performance under low wake velocity conditions, thereby enhancing the overall performance of the dual oscillating hydrofoils. The maximum efficiency and power coefficient of THDP are 0.445 and 0.678, respectively, reflecting increases of 34.0% and 24.9% compared to THIP.

Topics
Energy harvesting, Tidal energy, Computational fluid dynamics, Fluid wakes, Hydrodynamics, Vortex dynamics
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