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Formation of vortices and spanwise flow on an insect-like flapping wing throughout a flapping half cycle

Published online by Cambridge University Press:  27 January 2016

N. Phillips  and
K. Knowles
N. Phillips*
Affiliation:
Aeromechanical Systems Group, Cranfield University, Defence Academy of the UK, Shrivenham, UK
K. Knowles*
Affiliation:
Aeromechanical Systems Group, Cranfield University, Defence Academy of the UK, Shrivenham, UK
*
nathan.phillips@zoo.ox.ac.uk
k.knowles@cranfield.ac.uk
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Abstract

This paper presents an experimental investigation of the evolution of the leading-edge vortex and spanwise flow generated by an insect-like flapping-wing at a Reynolds number relevant to flapping-wing micro air vehicles (FMAVs) (Re = ~15,000). Experiments were accomplished with a first-of-its-kind flapping-wing apparatus. Dense pseudo-volumetric particle image velocimetry (PIV) measurements from 18% – 117% span were taken at 12 azimuthal positions throughout a flapping half cycle. Results revealed the formation of a primary leading-edge vortex (LEV) which saw an increase in size and spanwise flow (towards the tip) through its core as the wing swept from rest to the mid-stroke position where signs of vortex breakdown were observed. Beyond mid-stroke, spanwise flow decreased and the tip vortex grew in size and exhibited a reversal in its axial direction. At the end of the flapping half cycle, the primary LEV was still present over the wing surface, suggesting that the LEV remains attached to the wing throughout the entire flapping half cycle.

Type
Research Article
Information
The Aeronautical Journal , Volume 117 , Issue 1191 , May 2013 , pp. 471 - 490
Copyright
Copyright © Royal Aeronautical Society 2013 

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