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Lift enhancement and flow structure of airfoil with joint trailing-edge flap and Gurney flap

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Abstract

The impact of Gurney flaps (GF), of different heights and perforations, on the aerodynamic and wake characteristics of a NACA 0015 airfoil equipped with a trailing-edge flap (TEF) was investigated experimentally at Re = 2.54 × 105. The addition of the Gurney flap to the TEF produced a further increase in the downward turning of the mean flow (increased aft camber), leading to a significant increase in the lift, drag, and pitching moment compared to that produced by independently deployed TEF or GF. The maximum lift increased with flap height, with the maximum lift-enhancement effectiveness exhibited at the smallest flap height. The near wake behind the joint TEF and GF became wider and had a larger velocity deficit and fluctuations compared to independent GF and TEF deployment. The Gurney flap perforation had only a minor impact on the wake and aerodynamics characteristics compared to TEF with a solid GF. The rapid rise in lift generation of the joint TEF and GF application, compared to conventional TEF deployment, could provide an improved off-design high-lift device during landing and takeoff.

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Abbreviations

b :

Wing span

c :

Airfoil chord

C d :

Section drag coefficient

C l :

Section lift coefficient

C l,max :

Maximum lift coefficient

C l :

Lift-curve slope

C m :

Section pitching moment coefficient about ¼-chord

C m,peak :

Peak pitching moment coefficient

C p :

Surface pressure coefficient

d :

Perforation hole diameter

h :

Gurney flap height

Re :

Reynolds number, = U ∞ c/ν

u :

Mean streamwise velocity

u′:

Streamwise velocity fluctuation

U ∞ :

Freestream velocity

x, y, z:

Streamwise, transverse and spanwise direction

α:

Angle of attack

αss :

Static-stall angle

α zl :

Zero-lift angle

δ:

Trailing-edge flap deflection

σ:

Flap porosity

ζ:

Mean streamwise vorticity

ν:

Kinematic viscosity

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Acknowledgments

This work was supported by the Natural Science and Engineering Research Council (NSERC) of Canada. L.S. Ko is thanked for his help with the PIV experiment.

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Authors and Affiliations

  1. Department of Mechanical Engineering, McGill University, Montreal, QC, H3A 2K6, Canada

    T. Lee & Y. Y. Su

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  1. T. Lee
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  2. Y. Y. Su
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Correspondence to T. Lee.

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Lee, T., Su, Y.Y. Lift enhancement and flow structure of airfoil with joint trailing-edge flap and Gurney flap. Exp Fluids 50, 1671–1684 (2011). https://doi.org/10.1007/s00348-010-1024-8

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  • DOI: https://doi.org/10.1007/s00348-010-1024-8

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