Three-dimensional and clap-and-fling effects on a pair of flapping wings used for thrust generation

Abstract: This research investigates the three-dimensional effects of flow around a pair of flapping wings undergoing clap-and-fling interactions through harmonic in-plane motions combining pitching, heaving, and deviation. Both wings mirror each other in their movements. Baseline parameters were selected based on efficient configurations from a previous two-dimensional study. Simulations at a Reynolds number of 800 were conducted on wings in a thrust configuration utilizing the clap-and-fling mechanism. Rectangular flat-plate wings with various aspect ratios were evaluated to assess the impact of three-dimensional effects on performance. Results were compared with equivalent two-dimensional computations. It was found that the relative decrease in cycle-averaged efficiency due to three-dimensional effects can be limited to approximately 5.59% by using wings with an aspect ratio of 8, the largest considered in this work. Moreover, wing proximity inherent to clap-and-fling kinematics helps mitigate adverse three-dimensional effects.