Numerical study of the aerodynamic effects of bio-inspired leading-edge serrations on a heaving wing at a low Reynolds number

A numerical study with large-eddy simulation (LES) method is performed on the aerodynamic effects of bio-inspired leading-edge serrations on a wing in heaving motion at a low Reynolds number of Re=2×10⁴. During the research, rigorous contrastive simulations are performed for the baseline wing and the serrated ones. The baseline wing has a NACA0012 profile and the serrated ones are obtained by stretching/shrinking the leading portion of the baseline sinusoidally. Conclusive results show that leading-edge serrations can help reduce aerodynamic hysteresis and suppress dynamic-stall-induced load oscillations effectively. More importantly, serrated wings can be more efficient in lift production than the baseline, especially for relatively high reduced frequencies. In the currently covered parameter space, the largest lift efficiency improvement achieved by the leading-edge serrations can reach 15.92%, and the least improvement is 2.73%. Along with these good properties, the leading-edge serrations have induced larger drag, which indicates they are undesirable for propulsive motivations. Visualization of the flow fields reveals that a series of counter-rotating streamwise vortex pairs are dynamically induced by the leading-edge serrations. These streamwise vortices can act as momentum transporters and help enhance momentum exchange between low-energy boundary layer and high-energy outer flows, which can affect the flow structures as well as the aerodynamics of a heaving wing greatly. The current results may provide inspirations for improving aerodynamics, economies and stabilities of bionic underwater/aerial micro robots or any other devices which have heaving/flapping parts.