Trapping of a free vortex by Joukowski airfoils

Huang, Mingyang; Chow, Chuen‐Yen

doi:10.2514/3.7913

Cited by 59 publications

(25 citation statements)

References 2 publications

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“…A vortex held above a wing has long been known to be capable of enhancing lift (Gad-el-Hak and Ho, 1985;Gursul et al, 1994;Huang and Chow, 1982;Mourtos and Brooks, 1996;Riddle et al, 1999;Rossow, 1978Rossow, , 1992Rossow, , 1994Saffman and Sheffield, 1977). A transient LEV can be formed over an aerofoil by sudden changes in flow velocity or pitch (Délery, 2001).…”

mentioning

confidence: 99%

The aerodynamics ofManduca sexta: digital particle image velocimetry analysis of the leading-edge vortex

Bomphrey

Lawson

Harding

et al. 2005

Journal of Experimental Biology

164

168

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SUMMARY Here we present the first digital particle image velocimetry (DPIV)analysis of the flow field around the wings of an insect (the tobacco hawkmoth Manduca sexta, tethered to a 6-component force-moment balance in a wind tunnel). A leading-edge vortex (LEV) is present above the wings towards the end of the downstroke, as the net upward force peaks. Our DPIV analyses and smoke visualisations match the results of previous flow visualisation experiments at midwing, and we extend the experiments to provide the first analysis of the flow field above the thorax. Detailed DPIV measurements show that towards the end of the downstroke, the LEV structure is consistent with that recently reported in free-flying butterflies and dragonflies: the LEV is continuous across the thorax and runs along each wing to the wingtip, where it inflects to form the wingtip trailing vortices. The LEV core is 2-3 mm in diameter (approximately 10% of local wing chord) both at the midwing position and over the centreline at 1.2 m s-1 and at 3.5 m s-1flight speeds. At 1.2 m s-1 the measured LEV circulation is 0.012±0.001 m2 s-1 (mean ± s.d.) at the centreline and 0.011±0.001 m2 s-1 halfway along the wing. At 3.5 m s-1LEV circulation is 0.011±0.001 m2 s-1 at the centreline and 0.020±0.004 m2 s-1 at midwing. The DPIV measurements suggest that if there is any spanwise flow in the LEV towards the end of the downstroke its velocity is less than 1 m s-1. Estimates of force production show that the LEV contributes significantly to supporting body weight during bouts of flight at both speeds(more than 10% of body weight at 1.2 m s-1 and 35-65% of body weight at 3.5 m s-1).

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mentioning

confidence: 99%

The aerodynamics ofManduca sexta: digital particle image velocimetry analysis of the leading-edge vortex

Bomphrey

Lawson

Harding

et al. 2005

Journal of Experimental Biology

164

168

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show abstract

“…When there are no external boundaries such vortices have been studied both analytically and numerically by Saffman and Sheffield [9] when the airfoil is a flat plate and by Huang and Chow [5] in the case of Joukowski airfoils. Some computed examples when the airfoil is in a channel are given in [2].…”

Section: Applicationsmentioning

confidence: 99%

“…Conversely, any configuration of point vortices in stable equilibrium can be desingularized ([11], [12], [3])-Nevertheless, configurations of point vortices in equilibrium with respect to a fixed boundary have not been studied extensively. Saffman and Sheffield [9] and Huang and Chow [5] have considered a single vortex in equilibrium with respect to an airfoil. Section 3c below briefly discusses these vortices in the context of the present paper.…”

Section: Introductionmentioning

confidence: 99%

Equilibrium vortex configurations in domains with boundary

Miller¹

1998

Quart. Appl. Math.

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“…Figure 1-1d, where the ability to trap a vortex in a stationary position above the foil results in enormous lift coefficients [61,36]. The natural approach in this case is to look for steady solutions to the problem and then investigate their stability with a linearized model.…”

Section: The Conceptmentioning

confidence: 99%

Extracting energy from unsteady flows through vortex control

Streitlien¹

1994

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Trapping of a free vortex by Joukowski airfoils

Cited by 59 publications

References 2 publications

The aerodynamics ofManduca sexta: digital particle image velocimetry analysis of the leading-edge vortex

The aerodynamics ofManduca sexta: digital particle image velocimetry analysis of the leading-edge vortex

Equilibrium vortex configurations in domains with boundary

Extracting energy from unsteady flows through vortex control

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