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Title: Aerodynamic Efficiency of Gliding Birds vs. Comparable UAVs: a Review
Gliding birds perform feats that challenge even our most advanced similar-sized unmanned aerial vehicles (UAV). Their ostensible skill supports a pervasive belief that birds are highly efficient gliders that outperform modern UAVs. which led us to ask: are gliding birds truly more efficient than UAVs? Avian flight efficiency a well-studied topic and often cited as the inspiration for novel UAV designs. Despite the multitude of studies that have quantified the aerodynamic efficiency of gliding birds, there is no comprehensive summary of their findings. This is problematic because differing methodologies have inconsistent levels of uncertainty. As such, the lack of consolidated information on gliding bird efficiency inhibits a true comparison to UAVs. To fill this gap, we surveyed published theoretical and experimental estimates of avian aerodynamic efficiency and investigated the uncertainty of each method. We found that there was substantial variation in the aerodynamic efficiency predicted by different methods, which can lead to disparate conclusions on gliding bird efficiency. Our survey showed that measurements on live birds gliding in wind tunnels provide a reliable minimum estimate on a birds’ aerodynamic efficiency and allows the quantification of the wing configurations used in flight. Next, we surveyed the aeronautical literature to collect all published aerodynamic efficiencies of similar-sized, non-copter UAVs. The consolidated information allowed a direct comparison of modern UAVs and gliding birds. Contrary to our expectation, we found that there is no definitive evidence that any gliding bird species is either more or less efficient than a similar-sized UAV. This non-result highlights a critical need for new technology and analytical advances that can reduce the uncertainty associated with estimating a gliding bird’s aerodynamic efficiency. Nevertheless, our survey indicated that UAV designs informed by species flying within subcritical regimes may extend their operational range into lower Reynolds number regimes.  more » « less
Award ID(s):
1935216
NSF-PAR ID:
10301021
Author(s) / Creator(s):
;
Date Published:
Journal Name:
Bioinspiration biomimetics
Volume:
16
Issue:
3
ISSN:
1748-3182
Page Range / eLocation ID:
031001
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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