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Experimental investigation of the flow field of an oscillating airfoil and estimation of lift from wake surveys

Published online by Cambridge University Press:  26 April 2006

J. Panda  and
K. B. M. Q. Zaman
J. Panda
Affiliation:
NASA Lewis Research Center, Cleveland, OH 44135, USA
K. B. M. Q. Zaman
Affiliation:
NASA Lewis Research Center, Cleveland, OH 44135, USA
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Abstract

The flow field of an airfoil oscillated periodically over a reduced frequency range, 0 ≤ k ≤ 1.6, is studied experimentally at chord Reynolds numbers of Rc = 22000 and 44000. For most of the data, the NACA0012 airfoil is pitched sinusoidally about one quarter chord between angles of attack α of 5° and 25°. The cyclic variation of the near wake flow field is documented through flow visualization and phase-averaged vorticity measurements. In addition to the familiar dynamic stall vortex (DSV), an intense vortex of opposite sign is observed to originate from the trailing edge just when the DSV is shed. The two together take the shape of the cross-section of a large ‘mushroom’ while being convected away from the airfoil. The phase delay in the shedding of the DSV with increasing k, as observed by previous researchers, is documented for the full range of k. It is observed that the sum of the absolute values of all vorticity convected into the wake over a cycle is nearly constant and is independent of the reduced frequency and amplitude of oscillation but dependent on the mean α. The time varying component of the lift is estimated in a novel way from the shed vorticity flux. The analytical foundation of the method and the various approximations are discussed. The estimated lift hysteresis loops are found to be in reasonable agreement with available data from the literature as well as with limited force balance measurements. Comparison of the lift hysteresis loops with the corresponding vorticity fields clearly shows that major features of the lift variation are directly linked to the evolution of the large-scale vortical structures and the phase delay phenomenon.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 265 , 25 April 1994 , pp. 65 - 95
Copyright
© 1994 Cambridge University Press

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References

Batchelor, G. K. 1967 An Introduction to Fluid Dynamics. Cambridge University Press.
Bisplinghoff, R. L., Ashley, H. & Halfman, R. L. 1955 Aeroelasticity. Addison-Wesley.
Booth, E. R. 1987 Measurement of velocity and vorticity fields in the wake of an airfoil in periodic pitching motion. NASA TP 2780.Google Scholar
Carr, L. W. 1985 Dynamic stall – progress in analysis and prediction. AIAA paper 85-1769-CP, AIAA Atmospheric Flight Mechanics Conference.
Carr, L. W., McAlister, K. W. & McCroskey, W. J. 1977 Analysis of the development of dynamic stall based on oscillating airfoil experiments. NASA TN D-8382.Google Scholar
Cumpsty, N. A. 1989 Compressor Aerodynamics. Longman.
Gad-el-Hak, M. & Ho, C.-M. 1986 Unsteady vortical flow around three-dimensional lifting surfaces. AIAA J. 24 (5), 713–721.Google Scholar
Koochesfahani, M. M. 1987 Vortical patterns in the wake of an oscillating airfoil. AIAA Paper 87-0111.
Leishman, J. G. 1990 Dynamic stall experiments on the NACA 23012 aerofoil. Exps Fluids 9, 49–58.Google Scholar
McAlister, K. W. & Carr, L. W. 1979 Water tunnel visualization of dynamic stall. Trans. ASME I: J. Fluids Engng 106, 376–380.Google Scholar
McAlister, K. W., Carr, L. W. & McCroskey, W. J. 1978 Dynamic stall experiments on the NACA 0012 airfoil. NASA TP 1100.Google Scholar
McAlister, K. W., Pucci, S. L., McCroskey, W. L. & Carr, L. W. 1982 An experimental study of dynamic stall in advanced airfoil sections, vol. 2, pressure and force data. NASA TM 84245.
McCroskey, W. J. 1982 Unsteady airfoils. Ann. Rev. Fluid Mech. 14, 285–311.Google Scholar
Mehta, U. B. 1978 Dynamic stall of an oscillating airfoil. AGARD CP 227, paper 23.Google Scholar
Mathioulakis, D. S., Kim, M. J., Telionis, D. P. & Moor, D. T. 1985 On the wake of a pitching airfoil. AIAA paper 85-162.
Mueller, T. J. & Batill, S. M. 1982 Experimental studies of separation of a two-dimensional airfoil at low Reynolds numbers. AIAA J. 20, 463–475.Google Scholar
Ohmi, K., Coutanceau, M., Ta Phouc, Loc & Dulieu, A. 1990 Vortex formation around an oscillating and translating airfoil at large incidences. J. Fluid Mech. 211, 37–60.Google Scholar
Ohmi, K., Coutanceau, M., Daube, O. & Ta Phuoc, Loc 1991 Further experiments on vortex formation around an oscillating and translating airfoil at large incidences. J. Fluid Mech. 225, 607–630.Google Scholar
Panda, J. & Zaman, K. B. M. Q. 1992 Experimental investigation of the flowfield of an oscillating airfoil. AIAA Paper 92-2622.
Potter, M. C. & Foss, J. F. 1982 Fluid Mechanics. Great Lakes Press.
Reynolds, W. C. & Carr, L. W. 1985 Review of unsteady, driven, separated flows. AIAA Paper 85-0527.
Rice, E. J. & Zaman, K. B. M. Q. 1987 Control of shear flows by artificial excitation. AIAA Paper 87-2722.
Robinson, M. C., Helin, H. E. & Luttges, M. W. 1986 Control of wake structure behind an airfoil. AIAA Paper 86-2282.
Theodorsen, T. 1935 General theory of aerodynamic instability and the mechanism of flutter. NACA Rep. 496.
Visbal, M. R. 1991 On the formation and control of the dynamic stall vortex on a pitching airfoil. AIAA paper 91-0006.
Visbal, M. R. & Shang, J. S. 1988 Investigation of the flow structure around a rapidly pitching airfoil. AIAA J. 27 (8).Google Scholar
Von Kármán, T. & Burgers, J. M. 1943 General aerodynamic theory of perfect fluids. In Aerodynamic Theory, vol. 2 (ed. W. F. Durand). Durand reprinting committee, Pasadena, CA.
Von Kármán, T. & Seaars, W. R. 1938 Airfoil theory for non-uniform motion. J. Aeronaut. Sci. 5 (10), 379–390.Google Scholar
Westphal, R. V. & Mehta, R. D. 1984 Crossed hot-wire data acquisition and reduction system. NASA TM 85871.Google Scholar
Wu, J. C. 1981 Theory of aerodynamic force and moments in viscous flows. AIAA J. 19 (14), 432–441.Google Scholar
Wu, J.-C., Huff, D. L. & Sankar, L. N. 1990 Evaluation of three turbulence models in static air loads and dynamic stall predictions. J. Aircraft 27, 382–384.Google Scholar
Wu, J.-C., Kaza, K. R. V. & Sankar, L. N. 1987 A technique for the prediction of airfoil flutter characteristics in separated flow. AIAA Paper 87-0910.
Zaman, K. B. M. Q. & Hussain, A. K. M. F. 1981 Taylor hypothesis and large-scale coherent structures. J. Fluid Mech. 112, 379–396.Google Scholar
Zaman, K. B. M. Q. & McKinzie, D. J. 1991 Control of laminar separation over airfoils by acoustic excitation. AIAA J. 26 (7), 1075–1083.Google Scholar
Zaman, K. B. M. Q., McKinzie, D. J. & Rumsey, C. L. 1989 A natural low-frequency oscillation of the flow over an airfoil near stalling condition. J. Fluid Mech. 202, 403–442.Google Scholar