Dynamics of Bats’ Drinking Flight and Plant Leaf Interactions with Prof. Sunghwan Jung

Prof. Sunghwan (Sunny) Jung from Department of Biological and Environmental Engineering, Cornell University

“In nature, animals and plants exhibit interesting dynamics in the way they interact with air flows. In this presentation, I will discuss two intriguing examples that highlight how bats or plants disturb the surrounding air flows to achieve specific behaviors.

Bats possess extraordinary flight capabilities, relying on the intricate structure of their skeletal wings and flexible wing membranes. One remarkable maneuver is drinking while in flight, which necessitates specialized kinematics. In our study, we conduct a comparative analysis between straight flight and drinking flight modes in bats, utilizing a combination of experimental and theoretical approaches. High-speed video recordings are performed on two bat species, Hipposideros pratti and Rhinolophus ferrumequinum, within a controlled flight room. By conducting kinematic analysis and reconstructing landmark points in 3D, we observe that during drinking flight, bats reduce flapping amplitude while increasing flapping frequency compared to straight flight. Moreover, we perform aerodynamic analyses based on quasi-steady lift and drag force models for both forward flight and maneuvering flight during drinking.

Plant leaves, on the other hand, possess the ability to adapt and withstand fluidic stimuli in their natural environment. Rainfall, in particular, subjects plant leaves to impulsive stresses, causing them to twist, bend, and vibrate, ultimately leading to the dispersal of spores and allergens. These interactions between raindrops and leaves have raised several scientific questions and practical applications. As raindrops or wind forces act upon the lamina, the leaf undergoes twisting and bending motions. The vibrating motion of the leaf induces flow coherence and enhances the transport of spores. Through Lagrangian diagnostics, we have further discovered the presence of hyperbolic and elliptical coherent structures around fluttering leaves, providing a dynamic description of spore transport.

These studies shed light on the remarkable ways in which animals and plants manipulate air flows for their specific needs. Understanding these phenomena not only deepens our scientific knowledge but also holds potential for practical applications.”