Thrust enhancement of a flapping airfoil using a non-sinusoidal motion trajectories

A parametric numerical study is conducted to assess the effect of trajectory nature on the propulsive performances of a NACA0014 flapping airfoil. Sinusoidal and non-sinusoidal plunging and pitching trajectories are combined to achieve sought flapping trajectories. To this aim, the effect of kinematic parameters such as oscillation frequency, plunging amplitude, pitching amplitude, and phase angle between pitch and plunge is evaluated on thrust and propulsive efficiency behavior at a low Reynolds number, Re=1.1x104. It is found that the best propulsive efficiency is obtained for sinusoidal paths, while non-sinusoidal ones are found to slightly improve thrust and lift forces. Furthermore, thrust coefficient maximum values are obtained for non-sinusoidal trajectories when flatness coefficients S>1. The highest lift coefficient values are found however for flapping trajectories when flatness coefficients S<1.