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Fluids 2018, 3(2), 29; https://doi.org/10.3390/fluids3020029

Aerodynamics of a Wing with a Wingtip Flapper

1
Department of Aerospace and Mechanical Engineering, University of Arizona, 1130 N. Mountain Ave, Tucson, AZ 85721, USA
2
School of Automation Science and Electrical Engineering, Beihang University, Beijing 100191, China
3
Science and Technology on Aerospace Flight Dynamics Laboratory, Northwestern Polytechnical University, Xi’an 710072, China
This paper is a modified version of our paper “Aerodynamics of Wing with Oscillating Wingtip Flapper” published at the 34th AIAA Applied Aerodynamics Conference, AIAA AVIATION Forum, Washington, DC, USA, 13–17 June 2016.
*
Author to whom correspondence should be addressed.
Received: 22 March 2018 / Revised: 9 April 2018 / Accepted: 17 April 2018 / Published: 23 April 2018
(This article belongs to the Special Issue Bio-inspired Flow)
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Abstract

In the present study, an oscillating membrane flapper was pivotally attached to the tip of a conventional rigid wing. Stroke-averaged aerodynamic forces were measured for the range of the flapping frequency, showing significant increases in the lift coefficient and lift-to-drag ratio for the wing with a flapper. Major vortex patterns were deduced from observations of smoke-wire visualization and 2D phase-locked particle image velocimetry (PIV). The centerline of the primary vortex wanders in the counterclockwise direction. On the contrary, its core rotates in the same sense of rotation as a wingtip vortex in a conventional wing. The secondary weaker vortex of opposite rotation lasts for a half stroke. The vortex ring sheds from the flapper during the second half of the upstroke and pronation. The outer parts of the vortex system are much stronger than the inner ones. The circulation and size of vortices decrease significantly at the most distant station from the wing. Strong vertical jets were found in smoke-wire visualization and confirmed with velocity and vorticity fields obtained by PIV. These jets are formed between undulating vortices and inside of the vortex ring. The jet airflow moves away from the flapper and downward or upward depending on the flapping direction. View Full-Text
Keywords: wing; flapping; lift; drag; wake; vortex wing; flapping; lift; drag; wake; vortex
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Zhao, L.; Shkarayev, S.; Su, E. Aerodynamics of a Wing with a Wingtip Flapper. Fluids 2018, 3, 29.

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