The Effect of Non-sinusoidal Kinematics on Oscillating Hydrofoil Energy Extraction Efficiency*

Oscillating hydrofoil turbines are a promising environmentally friendly alternative to their conventional counterparts. However, optimizing their efficiency continues to be a research subject, primarily because the turbines' performance is affected by their kinematic trajectory, which is directly related to the angle of attack profile. Literature has explored whether sinusoidal or non-sinusoidal angle of attack profiles are more efficient. Although this is crucial question to be answered, it remains somewhat incomplete as the efficiency benefits are not determined by the angle of attack profile alone. A desired angle of attack profile can be achieved through multiple combinations of heave and pitch kinematics. The primary aim of this study is to determine if one combination exhibits a significant advantage over the other. To explore that, we compare the efficiencies of oscillating turbines utilizing the same angle of attack profiles, obtained from combinations of either sinusoidal heave and non-sinusoidal pitch, or non-sinusoidal heave and sinusoidal pitch motions. Numerical analyses are conducted using an advanced boundary element method with a leading edge separation model, and the results are also compared against experimental data for Re = 10,000.