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On vortex shedding from an airfoil in low-Reynolds-number flows

Published online by Cambridge University Press:  27 July 2009

SERHIY YARUSEVYCH ,
PIERRE E. SULLIVAN  and
JOHN G. KAWALL
SERHIY YARUSEVYCH*
Affiliation:
Department of Mechanical & Mechatronics Engineering, University of Waterloo, Waterloo, N2L 3G1, Canada
PIERRE E. SULLIVAN
Affiliation:
Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, M5S 3G8, Canada
JOHN G. KAWALL
Affiliation:
Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, M5B 2K3, Canada
*
†Email address for correspondence: [email protected]
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Abstract

Development of coherent structures in the separated shear layer and wake of an airfoil in low-Reynolds-number flows was studied experimentally for a range of airfoil chord Reynolds numbers, 55 × 103 ≤ Rec ≤ 210 × 103, and three angles of attack, α = 0°, 5° and 10°. To illustrate the effect of separated shear layer development on the characteristics of coherent structures, experiments were conducted for two flow regimes common to airfoil operation at low Reynolds numbers: (i) boundary layer separation without reattachment and (ii) separation bubble formation. The results demonstrate that roll-up vortices form in the separated shear layer due to the amplification of natural disturbances, and these structures play a key role in flow transition to turbulence. The final stage of transition in the separated shear layer, associated with the growth of a sub-harmonic component of fundamental disturbances, is linked to the merging of the roll-up vortices. Turbulent wake vortex shedding is shown to occur for both flow regimes investigated. Each of the two flow regimes produces distinctly different characteristics of the roll-up and wake vortices. The study focuses on frequency scaling of the investigated coherent structures and the effect of flow regime on the frequency scaling. Analysis of the results and available data from previous experiments shows that the fundamental frequency of the shear layer vortices exhibits a power law dependency on the Reynolds number for both flow regimes. In contrast, the wake vortex shedding frequency is shown to vary linearly with the Reynolds number. An alternative frequency scaling is proposed, which results in a good collapse of experimental data across the investigated range of Reynolds numbers.

Type
Papers
Information
Journal of Fluid Mechanics , Volume 632 , 10 August 2009 , pp. 245 - 271
Copyright
Copyright © Cambridge University Press 2009

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References

REFERENCES

Abdalla, I. E. & Yang, Z. 2004 Numerical study of the instability mechanism in transitional separating-reattaching flow. Intl J. Heat Fluid Flow 25, 593–605.CrossRefGoogle Scholar
Bloor, M. S. 1964 The transition to turbulence in the wake of a circular cylinder. J. Fluid Mech. 19, 290–303.CrossRefGoogle Scholar
Boiko, A. V., Grek, G. R., Dovgal, A. V. & Kozlov, V. V. 2002 The Origin of Turbulence in Near Wall Flows. Springer-Verlag.CrossRefGoogle Scholar
Brendel, M. & Mueller, T. J. 1988 Boundary-layer measurements on an airfoil at low Reynolds numbers. J. Aircr. 25, 612–617.CrossRefGoogle Scholar
Brendel, M. & Mueller, T. J. 1990 Transition phenomena on airfoils operating at low chord Reynolds numbers in steady and unsteady flow. In Numerical and Physical Aspects of Aerodynamic Flows IV (ed. Cebeci, T.), pp. 333–344. Springer-Verlag.CrossRefGoogle Scholar
Burgmann, S., Brucker, C. & Schroder, W. 2006 Scanning PIV measurements of a laminar separation bubble. Exp. Fluids 41, 319–326.CrossRefGoogle Scholar
Burgmann, S., Dannemann, J. & Schroder, W. 2008 Time-resolved and volumetric PIV measurements of a transitional separation bubble on an SD7003 airfoil. Exp. Fluids 44, 602–622.CrossRefGoogle Scholar
Burgmann, S. & Schroder, W. 2008 Investigation of the vortex induced unsteadiness of a separation bubble via time-resolved and scanning PIV measurements. Exp. Fluids 45, 675–691.CrossRefGoogle Scholar
Carmichael, B. H. 1981 Low Reynolds number airfoil survey. NASA CR 165803, Vol. I.Google Scholar
Dovgal, A. V., Kozlov, V. V. & Michalke, A. 1994 Laminar boundary layer separation: instability and associated phenomena. Prog. Aerosp. Sci. 30 61–94.CrossRefGoogle Scholar
Gaster, M. 1967 The structure and behaviour of separation bubbles. Tech. Rep. Reports and Memoranda No. 3595. Aeronautical Research Council, London.Google Scholar
Gerontakos, P. & Lee, T. 2005 Near wake behind an airfoil with leading-edge flow control. J. Aircr. 42, 561–567.CrossRefGoogle Scholar
Gerrard, J. H. 1966 The mechanics of the formation region of vortices behind bluff bodies. J. Fluid Mech. 25, 401–413.CrossRefGoogle Scholar
Haggmark, C. P., Bakchinov, A. A. & Alfredsson, P. H. 2000 Experiments on a two-dimensional laminar separation bubble. Phil. Trans. R. Soc. Lond. A 358, 3193–3205.CrossRefGoogle Scholar
Ho, C. & Huerre, P. 1984 Perturbed free shear layers. Annu. Rev. Fluid Mech. 16, 365–424.CrossRefGoogle Scholar
Hsiao, F. B., Liu, C. F. & Tang, Z. 1989 Aerodynamic performance and flow structure studies of a low Reynolds number airfoil. AIAA J. 27, 129–137.CrossRefGoogle Scholar
Huang, L. & Ho, C. 1990 Small-scale transition in a plane mixing layer. J. Fluid Mech 210, 475–500.CrossRefGoogle Scholar
Huang, R. F. & Lee, H. W. 2000 Turbulence effect on frequency characteristics of unsteady motions in wake of wing. AIAA J. 38, 87–94.CrossRefGoogle Scholar
Huang, R. F. & Lin, C. L. 1995 Vortex shedding and shear-layer instability of wing at low-Reynolds numbers. AIAA J 33, 1398–1403.CrossRefGoogle Scholar
Huang, R. F., Wu, J. Y., Jeng, J. H. & Chen, R. C. 2001 Surface flow and vortex shedding of an impulsively started wing. J. Fluid Mech. 441, 265–292.CrossRefGoogle Scholar
Kawall, J. G., Shokr, M. & Keffer, J. F. 1983 A digital technique for the simultaneous measurements of streamwise and lateral velocities in turbulent flows. J. Fluid Mech. 133, 83–112.CrossRefGoogle Scholar
Lang, M., Rist, U. & Wagner, S. 2004 Investigations on controlled transition development in laminar separation bubble by means of LDA and PIV. Exp. Fluids 36, 43–52.Google Scholar
LeBlanc, P., Blackwelder, R. & Liebeck, R. 1989 A comparison between boundary layer measurements in a laminar separation bubble flow and linear stability theory calculations. In Proceedings of Low Reynolds Number Aerodynamics Conference, Notre Dame, IN (ed. Mueller, T. J.), 189–205, Springer-Verlag.CrossRefGoogle Scholar
Lin, J. C. M. & Pauley, L. L. 1996 Low-Reynolds-number separation on an airfoil. AIAA J. 34, 1570–1577.CrossRefGoogle Scholar
Malkiel, E. & Mayle, R. E. 1996 Transition in a separation bubble. ASME J. Turbomach. 118, 752–759.CrossRefGoogle Scholar
Marxen, O. & Rist, U. 2005 Direct numerical simulation of nonlinear transitional stages in an experimentally investigated laminar separation bubble. In High Performance Computing in Science and Engineering '05 (ed. Nagel, W. E, Jager, W. & Resch, M.) pp. 103–117. Springer-Verlag.Google Scholar
Marxen, O., Rist, U. & Wagner, S. 2004 Effect of spanwise-modulated disturbances on transition in a separated boundary layer. AIAA J. 42, 937–944.CrossRefGoogle Scholar
McAuliffe, B. R. & Yaras, M. I. 2005 Separation-bubble-transition measurements on a low-Re airfoil using particle image velocimetry.In Proceedingsof the ASME Turbo Expo 2005, Reno, NV, GT2005-68663.Google Scholar
McAuliffe, B. R. & Yaras, M. I. 2007 Transition mechanisms in separation bubbles under low and elevated free stream turbulence. In Proceedings of the ASME Turbo Expo 2007, Montreal, Canada, GT2007-27605.Google Scholar
Miksad, R. W. 1972 Experiments on the nonlinear stages of free shear layer transition. J. Fluid. Mech. 56, 695–719.CrossRefGoogle Scholar
Mueller, T. J & DeLaurier, J. D. 2003 Aerodynamics of small vehicles. Annu. Rev. Fluid Mech. 35, 89–111.CrossRefGoogle Scholar
Prasad, A. & Williamson, C. H. K. 1997 The instability of the shear layer separating from a bluff body. J. Fluid Mech. 333, 375–402.CrossRefGoogle Scholar
Roshko, A. 1954 a On the development of turbulent wakes from vortex streets. NACA TR 1191.Google Scholar
Roshko, A. 1954 b On the drag and shedding frequency of two-dimensional bluff bodies. NACA TN 3169.Google Scholar
Roshko, A. 1993 Perspectives on bluff body aerodynamics. J. Wind Engng Ind. Aerodyn. 49, 79–100.CrossRefGoogle Scholar
Simmons, J. E. L. 1977 Similarities between two-dimensional and axisymmetric vortex wakes. Aeronaut. Q. 28, 15–20.CrossRefGoogle Scholar
Tani, I. 1964 Low speed flows involving bubble separations. Prog. Aerosp. Sci 5, 70–103.CrossRefGoogle Scholar
Thompson, M. C. & Hourigan, K. 2005 The shear-layer instability of a circular cylinder wake. Phys. Fluids 17 (021702), 1–4.CrossRefGoogle Scholar
Unal, M. F. & Rockwell, D. 1988 On vortex shedding from a cylinder. Part 1. The initial instability. J. Fluid Mech. 190, 491–512.CrossRefGoogle Scholar
Watmuff, J. H. 1999 Evolution of a wave packet into vortex loops in a laminar separation bubble. J. Fluid Mech. 397, 119–169.CrossRefGoogle Scholar
Williams-Stuber, K. & Gharib, M. 1990 Transition from order to chaos in the wake of an airfoil. J. Fluid Mech. 213, 29–57.CrossRefGoogle Scholar
Williamson, C. H. K. 1996 Vortex dynamics in the cylinder wake. Annu. Rev. Fluid Mech. 28, 477–539.CrossRefGoogle Scholar
Wilson, P. G. & Pauley, L. L. 1998 Two- and three-dimensional large-eddy simulations of a transitional separation bubble. Phys. Fluids 10, 2932–2940.CrossRefGoogle Scholar
Yang, Z. & Voke, P. R. 2001 Large-eddy simulation of boundary-layer separation and transition at a change of surface curvature. J. Fluid. Mech. 439, 305–333.CrossRefGoogle Scholar
Yarusevych, S. 2006 Investigation of airfoil boundary layer and turbulent wake development at low Reynolds numbers. PhD thesis, University of Toronto, Canada.CrossRefGoogle Scholar
Yarusevych, S., Sullivan, P. E. & Kawall, J. G. 2006 Coherent structures in airfoil boundary layer and wake at low Reynolds numbers. Phys. Fluids 18 (044101), 1–11.CrossRefGoogle Scholar
Zhang, W., Hain, R. & Kahler, J. 2008 Scanning PIV investigation of the laminar separation bubble on a SD7003 airfoil. Exp. Fluids 45, 725–743.CrossRefGoogle Scholar