Unique flow features of the silent southern Boobook owl wake during flapping flight
Jonathan Lawley, Hadar Ben-Gida, Krishnan Krishnamoorthy, Erin, Hackett, Gregory Kopp, Gareth Morgan, Christopher Guglielmo, Roi Gurka

TL;DR
This study investigates the unique wake flow features of the silent flight of the southern boobook owl, revealing chaotic wake patterns and vortex suppression mechanisms that contribute to its stealthy flight.
Contribution
It provides the first detailed characterization of owl wake dynamics during flapping flight, highlighting how owls manipulate flow structures for silent flight.
Findings
Owl wake is more chaotic with smaller vortices compared to other birds.
The pressure in the owl's wake is reduced to near zero, aiding noise suppression.
Owls manipulate wake vortices to minimize aeroacoustic signals.
Abstract
The mechanisms associated with an owls ability to fly silently have been the subject of scientific interest for many decades and a source of inspiration in the context of reducing noise in both flapping and non-flapping flight. Here, we characterize the near wake dynamics and associated flow structures that are produced by flying owls. The goal is to shed light on unique flow features that result from the owls wing morphology and its motion during forward flapping flight. We study the wake of the southern boobook owl (Ninox boobook); a mid-sized owl, which shares the common feature of stealthy flight. Three individual owls were flown, separately, in a climatic avian wind tunnel at their comfortable speed. The velocity field in the wake was sampled using long-duration highspeed Particle Image Velocimetry (PIV) while the wings kinematics were imaged simultaneously using high speed video.…
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Taxonomy
TopicsBiomimetic flight and propulsion mechanisms · Fluid Dynamics and Turbulent Flows · Hydrology and Sediment Transport Processes
