Ceiling effect of flapping wing rotorcrafts to enable energy-efficient perching

Abstract

Flapping wing rotorcrafts (FWRs) combine both the motion characteristics of flapping and rotary wings, exhibiting high aerodynamic efficiency at low Reynolds numbers. In this paper, the ceiling effect of FWRs has been studied through numerical and experimental methods to further investigate the aerodynamic performance of FWRs operating under a ceiling and to explore the feasibility of enhancing the flight efficiency of FWRs via ceiling-effect-based perching locomotion. Based on the momentum theory and blade element methods, a theoretical model is first established to predict the additional thrust generated by the FWR operating under the ceiling. Additionally, to uncover the detailed aerodynamic mechanisms of FWRs' ceiling effect, the computational fluid dynamics (CFD) simulations were conducted to analyze the changes in force production and flow field around the FWR at 75–115 mm distances from the ceiling. Furthermore, experimental methods were employed to validate the theoretical model and CFD simulation. The results demonstrate a continuous increase in the thrust from 19.18 to 22.15 gf as the ceiling distance decreases, while the total energy consumption remains relatively constant. Leveraging the ceiling effect, the tested FWR could achieve an additional lift force of up to 9.5% at 75 mm ceiling height with a 33 Hz flapping frequency. Finally, a ceiling perching demonstration was conducted to validate the feasibility of achieving FWRs' energy-efficient locomotion based on ceiling effects. Our study highlights the positive influence of ceiling effect on FWRs, showing a promising way to further improve the flight efficiency of FWRs.