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Transverse instability and low-frequency flapping in incompressible separated boundary layer flows: an experimental study

Published online by Cambridge University Press:  13 June 2012

Pierre-Yves Passaggia ,
Thomas Leweke  and
Uwe Ehrenstein
Pierre-Yves Passaggia
Affiliation:
IRPHE, UMR 7342 CNRS, Aix–Marseille Université, F-13384 Marseille CEDEX 13, France
Thomas Leweke*
Affiliation:
IRPHE, UMR 7342 CNRS, Aix–Marseille Université, F-13384 Marseille CEDEX 13, France
Uwe Ehrenstein
Affiliation:
IRPHE, UMR 7342 CNRS, Aix–Marseille Université, F-13384 Marseille CEDEX 13, France
*
†Email address for correspondence: thomas.leweke@irphe.univ-mrs.fr
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Abstract

The unstable dynamics of a transitional laminar separation bubble behind a two-dimensional bump geometry is investigated experimentally using dye visualizations and particle image velocimetry measurements. For Reynolds numbers above a critical value, the initially two-dimensional recirculation bubble is subject to modulations in the spanwise direction which can trigger vortex shedding. Increasing the Reynolds number further, the unstable behaviour is dominated by a low-frequency flapping motion, well known in transonic flows, and here investigated for the first time experimentally in an incompressible flow regime. These phenomena are characterized by non-intrusive measurements of the spatial structure and the frequencies of the unsteady motion. The results are in excellent agreement with previous numerical and theoretical predictions for the same geometry.

JFM classification

Boundary Layers: Boundary layer separation Instability: Instability
Type
Papers
Information
Journal of Fluid Mechanics , Volume 703 , 25 July 2012 , pp. 363 - 373
Copyright
Copyright © Cambridge University Press 2012

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References

1. Barkley, D., Gomes, M. G. M. & Henderson, R. D. 2002 Three-dimensional instability in flow over a backward-facing step. J. Fluid Mech. 473, 167–190.CrossRefGoogle Scholar
2. Beaudoin, J.-F., Cadot, O., Aider, J.-L. & Wesfreid, J. 2004 Three-dimensional stationary flow over a backward facing step. Eur. J. Mech. B 23, 147–155.CrossRefGoogle Scholar
3. Bernard, A., Foucaut, J. M., Dupont, P. & Stanislas, M. 2003 Decelerating boundary layer: a new scaling and mixing length model. AIAA J. 41, 248–255.CrossRefGoogle Scholar
4. Cherry, N. J., Hiller, R. & Latour, M. P. 1984 Unsteady measurements in a separating and reattaching flow. J. Fluid Mech. 144, 13–46.CrossRefGoogle Scholar
5. Cherubini, S., Robinet, J.-C. & De Palma, P. 2010a The effects of non-normality and nonlinearity of the Navier–Stokes operator on the dynamics of a large laminar separation bubble. Phys. Fluids 22, 014102.CrossRefGoogle Scholar
6. Cherubini, S., Robinet, J.-C., De Palma, P. & Alizard, F. 2010b The onset of three-dimensional centrifugal global modes and their nonlinear development in a recirculating flow over a flat surface. Phys. Fluids 22, 114102.CrossRefGoogle Scholar
7. Crouch, J. D., Garbaruk, A., Magidov, D. & Travin, A. 2009 Origin of transonic buffet in aerofoils. J. Fluid Mech. 628, 357–369.CrossRefGoogle Scholar
8. Dovgal, A. V., Kozlov, V. V. & Michalke, M. M. 1994 Laminar boundary layer separation: instability and associated phenomena. Prog. Aerosp. Sci. 30, 61–94.CrossRefGoogle Scholar
9. Ehrenstein, U. & Gallaire, F. 2008 Two-dimensional global low-frequency oscillations in a separating boundary-layer flow. J. Fluid Mech. 614, 315–327.CrossRefGoogle Scholar
10. Gallaire, F., Marquillie, M. & Ehrenstein, U. 2007 Three-dimensional transverse instabilities in detached boundary layers. J. Fluid Mech. 571, 221–233.CrossRefGoogle Scholar
11. Häggmark, 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
12. Kaiktsis, L., Karniadakis, G. E. & Orszag, S. A. 1996 Unsteadiness and convective instabilities in two-dimensional flow over a backward-facing step. J. Fluid Mech. 321, 157–187.CrossRefGoogle Scholar
13. Marquillie, M. & Ehrenstein, U. 2003 On the onset of nonlinear oscillations in a separating boundary-layer flow. J. Fluid Mech. 490, 169–188.CrossRefGoogle Scholar
14. Meunier, P. & Leweke, T. 2003 Analysis and treatment of errors due to high velocity gradients in particle image velocimetry. Exp. Fluids 35, 408–421.CrossRefGoogle Scholar
15. Pauley, L. L, Moin, P. & Reynolds, W. C. 1990 The structure of two-dimensional separation. J. Fluid Mech. 220, 397–411.CrossRefGoogle Scholar
16. Piponniau, S., Dussauge, J.-P., Debieve, J. & Dupont, P. 2009 A simple model for low-frequency unsteadiness in shock induced separation. J. Fluid Mech. 629, 87–108.CrossRefGoogle Scholar
17. Roy, C., Leweke, T., Thompson, M. C. & Hourigan, K. 2003 Experiments on the elliptic instability in vortex pairs with axial core flow. J. Fluid Mech. 677, 383–416.CrossRefGoogle Scholar
18. Sinha, S. N., Gupta, A. K. & Oberai, M. M. 1981 Laminar separating flow over backsteps and cavities. Part 1. Backsteps. AIAA J. 19, 1527–1530.CrossRefGoogle Scholar
19. Sirovich, L. 1987 Turbulence and the dynamics of coherent structures. J. Appl. Math. 45, 561–590.Google Scholar