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Characteristics of a wingtip vortex from an oscillating winglet

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Abstract

Initial perturbations in the wingtip vortices can potentially lead to instabilities that significantly reduce their lifetime in the wake of an aircraft. An active winglet capable of oscillating about its point of attachment to the main wing-section is developed using piezoelectric macro fiber composite, to actively perturb the vortex at its onset. Resonance characteristics of the actuated winglet oscillations are evaluated at different excitation levels and aerodynamic loading. Mean near-field characteristics of the vortex, developing from a stationary and an oscillating winglet, are investigated with the help of stereoscopic particle image velocimetry. Results show that the amplitude of winglet oscillations increases linearly with input excitation, to a highest attainable value of nearly four times the airfoil thickness at the winglet tip. The vortex developing from a winglet is stretched along its axis, having an elliptical core with non-uniform vorticity distribution. Actuation leads to spatial oscillations of the vortex core together with a reduction in the mean peak vorticity levels. The amplitude of the actuated core oscillations remains constant in the investigated region of the wake.

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Abbreviations

\(\alpha\) :

Angle of attack

\(\varLambda\) :

Angle of sweep

b :

Span of the experimental wing-section

\(C_{\rm m}\) :

Chord length at the mid-span of the wing-section

\(C_{\rm t}\) :

Chord length at the tip of the winglet

\(C_{\rm b}\) :

Chord length at the base of the winglet

\(C_{\rm p}\) :

Coefficient of pressure

\(\lambda\) :

Taper ratio (=\(C_{\rm t}\)/\(C_{\rm b}\))

\(U_{\infty }\) :

Freestream velocity

\(p_{\rm s}\) :

Static pressure on the airfoil surface

\(p_{\infty }\) :

Static pressure of the freestream

\(q_{\infty }\) :

Dynamic pressure of the freestream

Re :

Reynolds number

\(\omega\) :

Vorticity in the flow direction

\(\varGamma\) :

Circulation in a region

\(\mu\) :

Mean quantity

\(\sigma\) :

Standard deviation of a quantity

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Authors and Affiliations

  1. Department of Mechanical Engineering, FAMU-FSU College of Engineering, Florida State University, 2003 Levy Ave, Tallahassee, FL, 32310, USA

    T. K. Guha & R. Kumar

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  1. T. K. Guha
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  2. R. Kumar
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Correspondence to R. Kumar.

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Guha, T.K., Kumar, R. Characteristics of a wingtip vortex from an oscillating winglet. Exp Fluids 58, 8 (2017). https://doi.org/10.1007/s00348-016-2289-3

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