The Wing Kinematics Effects on Performance and Wake Structure Produced by Finite-Span Hovering Wings

Abstract

Throughout the past decades, the mechanisms of aerodynamic force production and lift augmentation in flapping insect wings have been the subject of many thorough computational, experimental, and analytical investigations. Despite the fact that in nature, insect wings tend to be of low or moderate aspect ratio, most experimental and numerical studies in this area have focused on examining large- or infinite-aspect-ratio flapping foils. Systematic efforts are still being expected for detailed investigations of finite aspect ratio flapping foil undergoing hovering motion due to the difficulties in both experimental and numerical methodologies. In the current study, a DNS solver for computing flows with moving immersed boundaries has been used to explore the wake structures and aerodynamic performance of finite aspect-ratio flapping foils undergoing two different hovering motions: optimal fruit fly motion and optimal bumblebee motion. The results of these numerical simulations indicate that the wake topologies of these relatively low aspect-ratio foils are significantly different from that observed for infinite-/largeaspect-ratio foils and vary with the kinematics. Lift augmentation has been studied for “clap-andfling” wing-wing interaction and associated wake structures are investigated, too.