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Petiolate wings: effects on the leading-edge vortex in flapping flight.
Interface Focus. 2017 Feb 06; 7(1):20160084.IF

Abstract

The wings of many insect species including crane flies and damselflies are petiolate (on stalks), with the wing planform beginning some distance away from the wing hinge, rather than at the hinge. The aerodynamic impact of flapping petiolate wings is relatively unknown, particularly on the formation of the lift-augmenting leading-edge vortex (LEV): a key flow structure exploited by many insects, birds and bats to enhance their lift coefficient. We investigated the aerodynamic implications of petiolation P using particle image velocimetry flow field measurements on an array of rectangular wings of aspect ratio 3 and petiolation values of P = 1-3. The wings were driven using a mechanical device, the 'Flapperatus', to produce highly repeatable insect-like kinematics. The wings maintained a constant Reynolds number of 1400 and dimensionless stroke amplitude Λ* (number of chords traversed by the wingtip) of 6.5 across all test cases. Our results showed that for more petiolate wings the LEV is generally larger, stronger in circulation, and covers a greater area of the wing surface, particularly at the mid-span and inboard locations early in the wing stroke cycle. In each case, the LEV was initially arch-like in form with its outboard end terminating in a focus-sink on the wing surface, before transitioning to become continuous with the tip vortex thereafter. In the second half of the wing stroke, more petiolate wings exhibit a more detached LEV, with detachment initiating at approximately 70% and 50% span for P = 1 and 3, respectively. As a consequence, lift coefficients based on the LEV are higher in the first half of the wing stroke for petiolate wings, but more comparable in the second half. Time-averaged LEV lift coefficients show a general rise with petiolation over the range tested.

Authors+Show Affiliations

Structure and Motion Laboratory, Royal Veterinary College , University of London , Hatfield AL9 7TA , UK.Aeromechanical Systems Group, Centre for Defence Engineering , Cranfield University , Defence Academy of the United Kingdom, Shrivenham SN6 8LA , UK.Structure and Motion Laboratory, Royal Veterinary College , University of London , Hatfield AL9 7TA , UK.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

28163876

Citation

Phillips, Nathan, et al. "Petiolate Wings: Effects On the Leading-edge Vortex in Flapping Flight." Interface Focus, vol. 7, no. 1, 2017, p. 20160084.
Phillips N, Knowles K, Bomphrey RJ. Petiolate wings: effects on the leading-edge vortex in flapping flight. Interface Focus. 2017;7(1):20160084.
Phillips, N., Knowles, K., & Bomphrey, R. J. (2017). Petiolate wings: effects on the leading-edge vortex in flapping flight. Interface Focus, 7(1), 20160084. https://doi.org/10.1098/rsfs.2016.0084
Phillips N, Knowles K, Bomphrey RJ. Petiolate Wings: Effects On the Leading-edge Vortex in Flapping Flight. Interface Focus. 2017 Feb 6;7(1):20160084. PubMed PMID: 28163876.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Petiolate wings: effects on the leading-edge vortex in flapping flight. AU - Phillips,Nathan, AU - Knowles,Kevin, AU - Bomphrey,Richard J, PY - 2017/2/7/entrez PY - 2017/2/7/pubmed PY - 2017/2/7/medline KW - flapping wing KW - insect flight KW - leading-edge vortex KW - micro air vehicle KW - petiolation SP - 20160084 EP - 20160084 JF - Interface focus JO - Interface Focus VL - 7 IS - 1 N2 - The wings of many insect species including crane flies and damselflies are petiolate (on stalks), with the wing planform beginning some distance away from the wing hinge, rather than at the hinge. The aerodynamic impact of flapping petiolate wings is relatively unknown, particularly on the formation of the lift-augmenting leading-edge vortex (LEV): a key flow structure exploited by many insects, birds and bats to enhance their lift coefficient. We investigated the aerodynamic implications of petiolation P using particle image velocimetry flow field measurements on an array of rectangular wings of aspect ratio 3 and petiolation values of P = 1-3. The wings were driven using a mechanical device, the 'Flapperatus', to produce highly repeatable insect-like kinematics. The wings maintained a constant Reynolds number of 1400 and dimensionless stroke amplitude Λ* (number of chords traversed by the wingtip) of 6.5 across all test cases. Our results showed that for more petiolate wings the LEV is generally larger, stronger in circulation, and covers a greater area of the wing surface, particularly at the mid-span and inboard locations early in the wing stroke cycle. In each case, the LEV was initially arch-like in form with its outboard end terminating in a focus-sink on the wing surface, before transitioning to become continuous with the tip vortex thereafter. In the second half of the wing stroke, more petiolate wings exhibit a more detached LEV, with detachment initiating at approximately 70% and 50% span for P = 1 and 3, respectively. As a consequence, lift coefficients based on the LEV are higher in the first half of the wing stroke for petiolate wings, but more comparable in the second half. Time-averaged LEV lift coefficients show a general rise with petiolation over the range tested. SN - 2042-8898 UR - https://www.unboundmedicine.com/medline/citation/28163876/Petiolate_wings:_effects_on_the_leading_edge_vortex_in_flapping_flight_ L2 - https://royalsocietypublishing.org/doi/full/10.1098/rsfs.2016.0084?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -
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