Computational and Experimental Analysis of Lift Generation of a Model Bird with Stationary and Dynamic Wing Configuration

Abstract

This work studies lift generation of the barn swallow through the use of computational and experimental analysis by progressively meeting finite dynamic constraints such as flapping amplitude and frequency. The lift generation was standardized for comparison and analysis using a dimensionless property of flying bodies called the lift coefficient. In this study, the barn swallow was selected because of its superior maneuverability and high flight efficiency with wings that morph when acting. As a first step, a true geometry of the bird was built via a three-dimensional (3-D) scan of a representative bird specimen. A computational fluid dynamics (CFD) software, ANSYS Fluent, was used to perform the numerical simulation under a uniform flow environment. An animation of a simplified lifting process of the representative model, characterized by a fuselage with stationary wings, was produced to visualize the fluid dynamics of the actual lifting process. For the experiment, a physical aerial robot prototype that mimicked the takeoff process of the bird in its natural environment was constructed without sweeping actuation. With this physical model, the lift coefficient generated by the flapping structure was measured and compared with that calculated from the numerical simulation of a stationary structure. The lift coefficient produced by the stationary airfoil from the numerical simulation was 0.215, and that produced by the dynamic wing from the experiment was determined to be no more than 0.347. Our analysis and measurements support the hypothesis that the lift generation was affected by the interaction between the fluid flow and the dynamic wing. In particular, we hypothesized that leading-edge vortices (LEVs) play an important role in lift generation and should be further parameterized for morphing-wing aerodynamics. This research can support the design of safer, more efficient, next-generation commercialaircraft with wing surfaces that can change shape or morph to improve flight control based on wing-flapping technology