The unsteady drag of airfoils having trailing edge flaps with overhang in subsonic flow

Abstract

A new analytical method, based on Theodorsen and Hariharan and Leishman’s work, which includes the influence of overhang on unsteady drag, is established to study the two-dimensional aerodynamics of trailing edge flap (TEF) airfoils with overhang. The drag of several TEF airfoils with overhang is calculated and precision improved effectively by the present methods in both steady and unsteady cases. The influence of flap chord ratio (the ratio of the flap chord to the airfoil chord) and overhang ratio (the ratio of overhang value to the flap chord) on steady and unsteady drags is analysed, which showed that (1) appearance of overhang increases the drag significantly, and (2) increase in overhang ratio results in augmenting amplitude and phase lag of drag coefficient. Unsteady lift force, pitching moment and hinge moment, of the TEF airfoils with overhang, for the sake of completeness, are also discussed together with the drag.

Keywords

trailing edge flap overhang drag

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References

Beddoes

Practical computation of unsteady lift. Vertica, 1984, 8(1), 55–71.

Leishman

J. G.

Beddoes

T. S.

A generalized model for airfoil unsteady aerodynamic behavior and dynamic stall using the indicial method. In Proceedings of the 42nd annual forum of AHS, Washington, DC, June 1986, 243–265.

Leishman

J. G.

Beddoes

A semi-empirical model for dynamic stall. J. Am. Helicopter Soc., 1989, 34(3), 3–17.

Leishman

J. G.

Two-dimensional model for airfoil unsteady drag below stall. J. Aircraft, 1988, 25(7), 665–666.

Theodorsen

General theory of aero-dynamic instability and mechanism of flutter. NACA Report-496, 1935, 413–433.

Hariharan

Leishman

J. G.

Unsteady aerodynamics of a flapped airfoil in subsonic flow by indicial concepts. AIAA, 1996, 34(7), 613–634.

Theodorsen

Garrick

I. E.

Nonstationary flow about a wing-aileron-tab combination including aerodynamic balance. NACA Report-736, 1942, 129–138.

Shen

Chopra

Aeroelastic modeling of trailing-edge flaps with smart material actuators. In Proceedings of the 41st AIAA/ASME/ASCE/AHS/ASC structure, structural dynamics, and materials conference, Atlanta, Georgia, 3–6 April 2000, AIAA-2000-1622, page 14.

Straub

F. K.

Charles

B. D.

Aeroelastic analysis of rotors with trailing edge flaps using comprehensive codes. J. Am. Helicopter Soc., 2001, 46(3), 192–199.

10.

Straub

F. K.

Kennedy

D. K.

Stemple

A. D.

Anand

V. R.

Birchette

T. S.

Development and whirl tower test of the smart active flap rotor. In Proceedings of SPIE: Smart structures and materials, San Diego, California, 14–18 March 2004, Vol. 5388, 202–212.

11.

Jose

A. I.

Baeder

J. D.

Steady and unsteady aerodynamic modeling of trailing edge flaps with overhang and gap using CFD and lower order models. In Proceedings of 47th AIAA aerospace sciences meeting including the new horizons forum and aerospace exposition, Orlando, Florida, 5–8 January 2009, AIAA-2009-1071, page 19.

12.

Milgram, J. A comprehensive aeroelastic analysis of helicopter main rotors with trailing edge flaps for vibration reduction. PhD Dissertation, University of Maryland, 1997.

13.

Theodorsen

General theory of aerodynamic instability and the mechanism of flutter, Report no. 496, 1935 (NACA, Washington, DC).

14.

Lemnios

A. Z.

Smith

A. F.

An analytical evaluation of the controllable twist rotor performance and dynamic behavior. USAAMRDL-TR-72-16, 1972.

15.

Beddoes

T. S.

Representation of airfoil behaviour. Vertica, 1983, 7(2), 183–197.

16.

Tijdeman

Schippers

Results of pressure measurements on an airfoil with oscillating flap intwo-dimensional high subsonic and transonic flow. National Aerospace Laboratory, 1973 (The Netherlands).

17.

Geissler

Sobieczky

Vollmers

Numerical study of the unsteady flow on a pitching airfoil with oscillating flap. In Proceedings of 24th European rotorcraft forum, Marseilles, France, 15–17 September 1998.