2013/01/01 by Christopher J. Clark, Damian O. Elias, Richard O. Prum · 3 citations
Engineering · #Fluid Dynamics and Vibration Analysis #Biomimetic flight and propulsion mechanisms #Aerodynamics and Acoustics in Jet Flows #Flutter #Hummingbird #Aeroelasticity #Feather #Vortex #Vibration #Acoustics #Flight feather #Physics #Aerodynamics #Mechanics #Zoology #Biology #Ecology
paper · doi:10.1242/jeb.080317
openalex publication_date 2013/01/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
Males in the 'bee' hummingbird clade produce distinctive, species-specific sounds with fluttering tail feathers during courtship displays. Flutter may be the result of vortex shedding or aeroelastic interactions. We investigated the underlying mechanics of flutter and sound production of a series of different feathers in a wind tunnel. All feathers tested were capable of fluttering at frequencies varying from 0.3 to 10 kHz. At low airspeeds (Uair) feather flutter was highly damped, but at a threshold airspeed (U*) the feathers abruptly entered a limit-cycle vibration and produced sound. Loudness increased with airspeed in most but not all feathers. Reduced frequency of flutter varied by an order of magnitude, and declined with increasing Uair in all feathers. This, along with the presence of strong harmonics, multiple modes of flutter and several other non-linear effects indicates that flutter is not simply a vortex-induced vibration, and that the accompanying sounds are not vortex whistles. Flutter is instead aeroelastic, in which structural (inertial/elastic) properties of the feather interact variably with aerodynamic forces, producing diverse acoustic results.