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Universal vortex formation time of flapping flight
Yukun Sun1, Emily Palmer2, Christopher Dougherty1
1Department of Biological and Environmental Engineering, Cornell University, Ithaca, NY 14853.
Summary
A new scaling law, the generalized vortex formation time, explains biological flight across species and conditions. This principle, based on maximizing leading-edge vortex circulation, offers a universal framework for understanding animal locomotion.
Area of Science:
- Aerodynamics
- Biomechanics
- Fluid Dynamics
Background:
- Biological flyers generate propulsion through appendage flapping, with flight kinematics studied via scaling laws.
- The Strouhal number (St) is a common metric for cruising flight but is condition-dependent.
- Leading-edge vortices (LEV) are crucial for generating propulsive forces in flapping flight.
Purpose of the Study:
- To develop a universal scaling law for biological flight independent of specific flight conditions.
- To generalize the concept of vortex formation time for flapping flight.
- To provide a unifying framework for understanding biolocomotion.
Main Methods:
- Developed a generalized vortex formation time based on LEV circulation maximization.
- Scaled the duration of vorticity injection with vorticity growth and maximum allowed vorticity.
- Compared the new scaling law with the Strouhal number from 28 species' flight data.
Main Results:
- The generalized vortex formation time is consistent across diverse animal flyers and cruising gaits.
- This new metric is independent of specific flight conditions, unlike the Strouhal number.
- Demonstrated a unifying framework for analyzing flapping flight dynamics.
Conclusions:
- The generalized vortex formation time offers a fundamental principle for understanding biological flight.
- This finding advances the study of complex wing kinematics in nature.
- Highlights a universal approach to biolocomotion analysis.
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