Effect of Symmetric Delay on Airfoil Plunging

Delaying the sinusoidal plunging in the middle of the up- and down stroke is studied. This form of kinematics can appear if the flapping mechanism is malfunctioning, or while large birds fly in some cases. Aim of this study is to understand the effect of pausing the airfoil during plunging in the equilibrium position. The paused plunging is modelled mathematically by means of a sinusoidal waveform raised to the third power. Evaluation of this waveform is done on two stages; the wake pattern analysis and the aerodynamic and propulsive analysis. Studying this waveform reveals a robust way to generate two triads wake pattern instead of the regular reverse von Karman vortex wake pattern. The thrust generation mechanism is presented. The performance evaluation is done based on the thrust, lift, and power coefficients and the propulsive efficiency at different point in the nondimensional amplitude- reduced frequency space. Regression modeling methods are utilized to stand on the performance of the paused waveform with respect to the regular sinusoidal waveform. These findings underscore the potential of the proposed waveform as a promising alternative for enhancing the aerodynamic performance and propulsive efficiency in the design of Micro Air Vehicles (MAVs), a rapidly evolving field.