Enhancement Mechanism of Non-Sinusoidal Trajectory on Dual-Flapping-Wing Energy Harvesting Across Three Layouts

Flapping-wing energy harvesting is a promising technology for distributed wind energy utilization, yet the enhancement mechanism of non-sinusoidal motion trajectories across different dual-wing configurations remains insufficiently elucidated. This work investigates the performance characteristics and underlying flow physics of dual-flapping-wing energy harvesting systems under three typical layouts. Numerical simulations are conducted to compare the harvesting performance of staggered, tandem, and parallel arrangements under both sinusoidal and non-sinusoidal trajectories, with wake vortex structures and aerodynamic forces systematically analyzed. Results indicate that the staggered arrangement achieves the highest efficiency of 68% within the present two-dimensional framework under non-sinusoidal motion, followed by the parallel arrangement (63.2%) and the tandem arrangement (58.3%). The aft wing is identified as the decisive factor governing the overall system performance, while a well-ordered wake vortex pattern is identified as a key characteristic associated with high-efficiency operation. The non-sinusoidal trajectory facilitates vortex merging and orderly arrangement, which enlarges the pressure difference across the airfoil and substantially enhances heaving power output. The staggered configuration combined with the non-sinusoidal trajectory, is recommended as a promising design, providing a reference for the design of multi-flapping-wing energy harvesting systems.