Optimal Power Extraction Conditions for Oscillating Foils Using Non-Sinusoidal Motions

We present novel experiments and simulations of the power extraction performance of heaving and pitching foils. Previous studies have suggested that the angle of attack (AoA) waveform is important for maximizing the performance rather than the heave or pitch motion. However, a prescribed sinusoidal AoA waveform may be achieved with two approaches: (1) sinusoidal heave with a non-sinusoidal pitch or (2) sinusoidal pitch with a non-sinusoidal heave. We compare both approaches for a wide range of AoA, Strouhal number, and dimensionless amplitude to determine whether the two approaches produce invariant performance or whether heave or pitch is preferred as a sinusoidal motion. We consider a three-dimensional NACA0015 airfoil with an aspect ratio of four and pitching about the one-third chord at a Reynolds number of Re = 10,000.