Formation, structure, and development of near-field wing tip vortices

Karakuş, Cuma; Akıllı, Hüseyin; Şahi̇n, Beşi̇r

doi:10.1243/09544100jaero274

Cited by 17 publications

(9 citation statements)

References 14 publications

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“…PIV measurements on squared tip by Birch et al [8] confirmed the multiple vortices structure in the initial rolling-up of the vortex and they showed both axial velocity deficit and excess in the vortex centre at a distance of 1.5 chords from the trailing edge. Karakus et al [9] concluded that the tip region is dominated by the strong interaction between the multiple secondary vortices and the primary vortex. Zuhal and Gharib [10] found this interaction also in the wake up to 3 chords of distance from the wing; they also found a correlation between a higher fluctuation of the primary vortex location and the presence of strong secondary vortices.…”

Section: Introductionmentioning

confidence: 99%

Vortex formation on squared and rounded tip

Giuni

Green

2013

Aerospace Science and Technology

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The vortical flow originated from the tip of a NACA 0012 rectangular wing is described in its initial formation and development over a rounded and a squared tip. Smoke visualizations show the rolling-up kinematic and evolution of the vortical systems moving the plane towards the trailing edge. The presence of intense secondary vortices affects the primary vortex unsteadiness and shape during the formation and in the early wake. Stereoscopic Particle Image Velocimetry is used to describe vorticity, axial velocity and turbulent kinetic energy distributions of the vortex during the formation and in the early wake at different angles of attack of the wing. The rolling-up of the vorticity sheet around the vortex system is strongly influenced by the vortex shape and the intensity of secondary vortices. Turbulence coming from secondary structures and shear layers is wrapped into the roll-up of the vortex and high levels of turbulence are measured in the vortex core. However, a laminar vortex core is observed for the lower angle of attack in the early wake. Comparing the meandering of the vortex for the two wingtip geometries, two different sources of the vortex fluctuation in the wake are identified: the interaction of secondary vortices moving around the primary vortex and the rolling-up of the vorticity sheet. Lastly, measurements in the wake of the wing at zero incidence are also presented showing a distinctive counter rotating vortex pair.

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Section: Introductionmentioning

confidence: 99%

Vortex formation on squared and rounded tip

Giuni

Green

2013

Aerospace Science and Technology

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“…Several possible definitions of the vortex core location exist; the method used in this work was the location of maximum (absolute) vorticity. 6,28 The advantage of this procedure was in its ease of implementation. However, only a few points are used when calculating the velocity gradients meaning that this method is sensitive to spurious velocity data.…”

Section: Particle Image Velocimetry Measurementsmentioning

confidence: 99%

“…Tip vortices shed from rotor and wind turbine blades can lead to rotor noise, mechanical fatigue, and vibration. 1,6 Lastly, various research has identified the flap side edge vortex as being an important component of high lift device noise. 7 Therefore, any new flow control technique developed that can control the tip vortex flow field could have a wide range of applications.…”

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confidence: 99%

“…1,2,9,10 In the near field, several studies have examined the initial roll-up, the subsequent evolution, and possible means of controlling the tip vortex. 5,6,[11][12][13][14][15] These studies concluded that the trailing edge shear layer roles up rapidly into a spiral that gets tighter as the flow proceeds downstream and eventual forms a vortex. Despite the speed of the initial roll-up, it takes distances of several tens or even hundreds of wing chord lengths downstream for the vortex to become fully developed.…”

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confidence: 99%

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Active Control of a Wing Tip Vortex with a Dielectric Barrier Discharge Plasma Actuator

Chappell

Angland

2012

6th AIAA Flow Control Conference

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An experimental investigation has been conducted into the active control of a wing tip vortex with a dielectric barrier discharge plasma actuator. The actuator was placed around the wing tip with the momentum added in the opposite direction to that of the cross stream flow. Particle image velocimetry measurements were performed on a low aspect ratio rounded tip NACA 0015 wing in a low speed wind tunnel at a maximum Reynolds number of 2.8 ×10 5 , based on the wing chord. Experiments were performed at various angles of attack. The current strength of the plasma actuator limited the maximum freestream velocity to 15 ms −1 . For low angles of attack (2 • and 6 • ), the near field results showed an increase in vortex size and a reduction in the core circulation when control was applied. The effectiveness of the actuator reduced with freestream velocity and angle of attack. The use of the plasma actuator was found to increase the velocity fluctuations close to the surface of the wing. At an angle of attack of 14 • , the actuator resulted in a smaller vortex and an increase in the core circulation. It was hypothesised that at this high angle of attack, the vorticity generated at the suction side electrodes was fed into the core, increasing the strength of the tip vortex. The results show that the potential of the plasma actuator for the near field control of the tip vortex is promising provided the angle of attack is low. NomenclatureA * Non-dimensionalised bounded within area of integration AR Aspect ratio b w Wing span, m C L Wing lift coefficient c Wing chord, m Re c Reynolds number based on main element chord r Radial distance measured from vortex centre, mm r 1 Radius of vortex, mm r max Maximum radial distance measured from vortex centre, mm S Surface area, m 2 s Wing semi-span, m t w Wing thickness, m U ∞ Freestream velocity, ms −1 v rms Root mean square velocity component in y direction, ms −1 v * θ Non-dimensionalised tangential velocity x, y, z Coorindates measured from model leading edge tip, m y c , z c Vortex centroid, m * PhD Student, Faculty of Engineering and the Environment. Student Member AIAA † Research Fellow, Faculty of Engineering and the Environment, Member AIAA.

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“…In particular, the near-field structure has been measured using different experimental techniques. [27][28][29][30] Experimental measurements several chords downstream, which are more relevant for the present work, have been recently made, using LDA and/or particle image velocimetry ͑PIV͒ techniques, by Devenport et al 31 and by Roy. 32 These authors fitted their experimental results to a q-vortex model and to a two-core scales vortex model, respectively.…”

Section: Introductionmentioning

confidence: 99%

Structure of trailing vortices: Comparison between particle image velocimetry measurements and theoretical models

et al. 2011

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The velocity field of the trailing vortex behind a wing at different angles of attack has been measured through the stereo particle image velocimetry technique in a water tunnel for Reynolds numbers between 20 000 and 40 000, and for several distances to the wing tip. After filtering out the vortex meandering, the radial profiles of the axial and the azimuthal velocity components and of the radial profiles of the vorticity were compared to the theoretical models for trailing vortices by ͓G. K. Batchelor, J. Fluid Mech. 20, 645 ͑1964͔͒ and by ͓D. W. Moore and P. G. Saffman, Proc. R. Soc. London, Ser. A 333, 491 ͑1973͔͒, whose main features are conveniently summarized. We take into account the downstream evolution of these profiles from just a fraction of the wing chord to more than ten chords. The radial profiles of the vorticity and the azimuthal velocity are shown to fit quite well to Moore and Saffman's trailing vortex model, while Batchelor's model does not fit so well, especially in the tails of the profiles. At the downstream distances considered, the radial profiles of the axial velocity do not adjust so well to Moore and Saffman's model as the azimuthal velocity profiles do, but the disagreement with Batchelor's model is quite manifested, especially at the axis. Thus, the details of the flow structure are in better agreement with the predictions of Moore and Saffman's model. The downstream evolution of several key features of the measured velocity profiles is also in agreement with the predictions of Moore and Saffman's model, within the dispersion of the experimental data, but up to the largest axial distance considered in this work we cannot decide if they follow the asymptotic behavior predicted by this model.

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Formation, structure, and development of near-field wing tip vortices

Cited by 17 publications

References 14 publications

Vortex formation on squared and rounded tip

Vortex formation on squared and rounded tip

Active Control of a Wing Tip Vortex with a Dielectric Barrier Discharge Plasma Actuator

Structure of trailing vortices: Comparison between particle image velocimetry measurements and theoretical models

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