On plunging using double-peak kinematics

This study investigates the thrust generation mechanism and performance of a plunging airfoil undergoing double-peak periodic motion, specifically utilizing superposition of the regular sinusoidal waveform with another less-weighted faster one. It is revealed that the proposed waveform produces 200% more thrust when compared to sinusoidal plunging with a small efficiency difference. Also, it produces two vortex pairs (2P) per cycle all over the plunging frequency-amplitude space, instead of the reverse von Karman vortices. Using this proposed waveform, the 2P wake is generated through interaction of three types of vortices shed during plunging, opposing the regular 2P pattern found in the literature.