Don't be rigid, be BILLY

Alexander Gehrke, École polytechnique fédérale de Lausanne
Jules Richeux, École polytechnique fédérale de Lausanne
Karen Mulleners, École polytechnique fédérale de Lausanne

DOI: https://doi.org/10.1103/APS.DFD.2021.GFM.V0011

Many natural fliers like bats and insects show remarkable flight abilities. Their efficient and agile maneuvering relies on lightweight and compliant wings. In this video, we present BILLY, a Bio-Inspired Lightweight and Limber wing prototYpe designed for robotic flapping wing systems. The membrane wing holder is equipped with a rotating leading edge which aligns with the incoming flow and a chordwise translating trailing edge which allows for passive cambering. To find the kinematics that let BILLY yield highest aerodynamic lift and efficiency in hovering flight, we conducted an in-situ experimental optimization.This video shows the evolution of the flapping kinematics towards the optimal solutions and highlights how the deformation of the membrane wing leads to improved aerodynamic performance compared to rigid wings. We visualize the flow around the wing using particles illuminated by a light sheet. From the flow visualization, we see the formation of a stable leading edge vortex on the wing promoting the lift production on the wing.

See other videos from the 2021 Gallery of Fluid Motion: https://gfm.aps.org/