Dynamic Analysis of Ground Effect Conditions on the Aerodynamic Efficiency of a Bat-inspired Robotic Wing, `Chiropter'

For decades, aircraft have leveraged ground effect—a phenomenon that increases lift and decreases drag on surfaces near the ground—to enhance flight efficiency. However, its influence on low-Reynolds-number flight, relevant for small unmanned aerial vehicles (sUAVs), is vastly underexplored. Notably, small organisms that frequently hunt, cruise, and forage near the ground appear to illustrate a rich source of inspiration for driving better sUAV design in this regime.

 

This paper thus investigates the performance of a bat-inspired wing, “Chiropter”, modeled after the well-studied species Cynopterus brachyotis, when subjected to an engineered ground effect boundary. 

A comparative study between a conventional NACA 2414 airfoil and bat-inspired planforms was conducted in Princeton University’s wind tunnel. Force measurements were acquired in the wind tunnel’s test section (1.2 x 1.2 m cross section, 1 m long) at a Reynolds number around 30,000 while the wings were subjected to an engineered ground effect boundary—a belt-driven system that eliminated the introduction of boundary layers. 

The results of this study not only improve understanding of how bats leverage ground effect but also inform small-scale aerial vehicle design for efficient, stable flight in these regimes. ​​​​​​​