Abstract
The oscillating hydrofoil represents a promising technology for harvesting energy from tidal currents. While previous research has primarily focused on oscillating hydrofoils utilizing a fully activated control strategy, the industry predominantly employs a semi-activated control strategy in existing tidal current energy converters. It is essential to identify the differences in predicted energy-harvesting performance between these two controlling strategies through experimental modeling or numerical studies. Furthermore, the suitability of the fully activated control strategy in predicting the energy-harvesting capabilities of oscillating hydrofoils is evaluated. The 2D numerical models of hydrofoil based on fully activated and semi-activated control strategies have been developed and validated. The amplitudes of heaving and pitching movements for the fully activated hydrofoil are determined to match those of the semi-activated hydrofoil. The results show that the main difference between the two control strategies lies in the phase shift occurring between the pitching and heaving motions. This phase shift affects the lift force and its coordination with the heaving velocity, which in turn affects the power output. Notably, the maximum relative efficiency difference obtained between the fully activated and semi-activated control strategies can reach 191%.