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Disturbance growth in a laminar separation bubble subjected to free-stream turbulence

Published online by Cambridge University Press:  09 February 2023

Tomek Jaroslawski Open the ORCID record for Tomek Jaroslawski [Opens in a new window] ,
Maxime Forte ,
Olivier Vermeersch Open the ORCID record for Olivier Vermeersch [Opens in a new window] ,
Jean-Marc Moschetta  and
Erwin R. Gowree Open the ORCID record for Erwin R. Gowree [Opens in a new window]
Tomek Jaroslawski*
Affiliation:
ONERA, DMPE, Universite de Toulouse, 31055 Toulouse, France
Maxime Forte
Affiliation:
ONERA, DMPE, Universite de Toulouse, 31055 Toulouse, France
Olivier Vermeersch
Affiliation:
ONERA, DMPE, Universite de Toulouse, 31055 Toulouse, France
Jean-Marc Moschetta
Affiliation:
ISAE-SUPAERO, Universite de Toulouse, 31055 Toulouse, France
Erwin R. Gowree
Affiliation:
ISAE-SUPAERO, Universite de Toulouse, 31055 Toulouse, France
*
†Email address for correspondence: [email protected]
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Abstract

Experiments were conducted to study the transition and flow development in a laminar separation bubble (LSB) formed on an aerofoil. The effects of a wide range of free-stream turbulence intensity ($0.15\,\%< Tu<6.26\,\%$) and streamwise integral length scale ($4.6\ {\rm mm}<\varLambda _{u}<17.2\ {\rm mm}$) are considered. The co-existence of modal instability due to the LSB and non-modal instability caused by streaks generated by free-stream turbulence is observed. The flow field is measured using hot-wire anemometry, which showed that the presence of streaks in the boundary layer modifies the mean-flow topology of the bubble. These changes in the mean flow field result in the modification of the convective disturbance growth, where an increase in turbulence intensity is found to dampen the growth of the modal instability. For a relatively fixed level of $Tu$, the variation of $\varLambda _{u}$ has modest effects. However, a slight advancement of the nonlinear growth of disturbances and eventual breakdown with the decrease in $\varLambda _{u}$ is observed. The data show that the streamwise growth of the disturbance energy is exponential for the lowest levels of free-stream turbulence and gradually becomes algebraic as the level of free-stream turbulence increases. Once a critical turbulence intensity is reached, there is enough energy in the boundary layer to suppress the laminar separation bubble, resulting in the non-modal instability taking over the transition process. Linear stability analysis is conducted in the fore position of the LSB. It accurately models incipient disturbance growth, unstable frequencies and eigenfunctions for configurations subjected to turbulence intensity levels up to 3 %, showing that the mean-flow modification due to the non-modal instability dampens the modal instability.

JFM classification

Boundary Layers: Boundary layer stability Boundary Layers: Boundary layer separation
Type
JFM Papers
Information
Journal of Fluid Mechanics , Volume 956 , 10 February 2023 , A33
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© The Author(s), 2023. Published by Cambridge University Press

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References

Andersson, P., Berggren, M. & Henningson, D.S. 1999 Optimal disturbances and bypass transition in boundary layers. Phys. Fluids 11 (1), 134–150.CrossRefGoogle Scholar
Arnal, D. & Julien, J.C. 1978 Contribution expérimentale à l'etude de la receptivité d'une couche limite laminaire, à la turbulence de l’écoulement generale. Tech. Rep. 1/5018 AYD.Google Scholar
Balzer, W. & Fasel, H. 2016 Numerical investigation of the role of free-stream turbulence in boundary-layer separation. J. Fluid Mech. 801, 289–321.CrossRefGoogle Scholar
Benedict, L.H. & Gould, R.D. 1996 Towards better uncertainty estimates for turbulence statistics. Exp. Fluids 22 (2), 129–136.CrossRefGoogle Scholar
Boutilier, M.S.H. & Yarusevych, S. 2012 Separated shear layer transition over an airfoil at a low Reynolds number. Phys. Fluids 24 (8), 084105.CrossRefGoogle Scholar
Boutilier, M.S.H. & Yarusevych, S. 2013 Sensitivity of linear stability analysis of measured separated shear layers. Eur. J. Mech. (B/Fluids) 37, 129–142.CrossRefGoogle Scholar
Boutilier, M.S.H. 2011 Experimental investigation of transition over a NACA 0018 airfoil at a low Reynolds number. Master's thesis, University of Waterloo.Google Scholar
Brandt, L., Schlatter, P. & Henningson, D.S. 2004 Transition in boundary layers subject to free-stream turbulence. J. Fluid Mech. 517, 167.CrossRefGoogle Scholar
Breuer, M. 2018 Effect of inflow turbulence on an airfoil flow with laminar separation bubble: an LES study. Flow Turbul. Combust. 101 (2), 433–456.CrossRefGoogle Scholar
Bridges, T.J. & Morris, P.J. 1984 Differential eigenvalue problems in which the parameter appears nonlinearly. J. Comput. Phys. 55 (3), 437–460.CrossRefGoogle Scholar
Bruun, H.H. 1996 Hot-wire Anemometry: Principles and Signal Analysis. Oxford University Press.Google Scholar
Burattini, P. & Antonia, R.A. 2005 The effect of different X-wire calibration schemes on some turbulence statistics. Exp. Fluids 38 (1), 80–89.CrossRefGoogle Scholar
Burgmann, S. & Schröder, W. 2008 Investigation of the vortex induced unsteadiness of a separation bubble via time-resolved and scanning PIV measurements. Exp. Fluids 45 (4), 675–691.CrossRefGoogle Scholar
Carmichael, B.H. 1981 Low Reynolds number airfoil survey, volume 1. NASA Contractor Rep. 165803.Google Scholar
Cherubini, S., Robinet, J.-Ch. & De Palma, P. 2010 The effects of non-normality and nonlinearity of the Navier–Stokes operator on the dynamics of a large laminar separation bubble. Phys. Fluids 22 (1), 014102.CrossRefGoogle Scholar
Dellacasagrande, M., Barsi, D., Lengani, D., Simoni, D. & Verdoya, J. 2020 Response of a flat plate laminar separation bubble to Reynolds number, free-stream turbulence and adverse pressure gradient variation. Exp. Fluids 61 (6).CrossRefGoogle Scholar
Diwan, S.S. & Ramesh, O.N. 2009 On the origin of the inflectional instability of a laminar separation bubble. J. Fluid Mech. 629, 263–298.CrossRefGoogle Scholar
Dovgal, A.V., Kozlov, V.V. & Michalke, A. 1994 Laminar boundary layer separation: instability and associated phenomena. Prog. Aerosp. Sci. 30 (1), 61–94.CrossRefGoogle Scholar
Drela, M. 1989 XFOIL: an analysis and design system for low Reynolds number airfoils. In Low Reynolds Number Aerodynamics (ed. T.J. Mueller), Lecture Notes in Engineering, vol. 54, pp. 1–12. Springer.CrossRefGoogle Scholar
Fransson, J.H.M., Matsubara, M. & Alfredsson, P.H. 2005 Transition induced by free-stream turbulence. J. Fluid Mech. 527, 1–25.CrossRefGoogle Scholar
Fransson, J.H.M. & Shahinfar, S. 2020 On the effect of free-stream turbulence on boundary-layer transition. J. Fluid Mech. 899, A23.CrossRefGoogle Scholar
Gaster, M. 1967 The structure and behaviour of laminar separation bubbles. Tech. Rep. 3595. Aeronautical Research Council.Google Scholar
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 (1777), 3193–3205.CrossRefGoogle Scholar
Häggmark, C.P., Hildings, C. & Henningson, D.S. 2001 A numerical and experimental study of a transitional separation bubble. Aerosp. Sci. Technol. 5 (5), 317–328.CrossRefGoogle Scholar
Hislop, G.S. 1940 The transition of a laminar boundary layer in a wind tunnel. PhD thesis, University of Cambridge.Google Scholar
Hosseinverdi, S. 2014 Influence of free-stream turbulence on laminar-turbulent transition in long laminar separation bubbles: direct numerical simulations. Master's thesis, University of Arizona.CrossRefGoogle Scholar
Hosseinverdi, S. & Fasel, H. 2019 Numerical investigation of laminar–turbulent transition in laminar separation bubbles: the effect of free-stream turbulence. J. Fluid Mech. 858, 714–759.CrossRefGoogle Scholar
Houdeville, R. 1992 Three-dimensional boundary layer calculation by a characteristic method. In Fifth Symposium on Numerical and Physical Aspects of Aerodynamic Flows, Long Beach, January 1992. California State University.Google Scholar
Hurst, D. & Vassilicos, J.C. 2007 Scalings and decay of fractal-generated turbulence. Phys. Fluids 19 (3), 035103.CrossRefGoogle Scholar
Istvan, M.S. & Yarusevych, S. 2018 Effects of free-stream turbulence intensity on transition in a laminar separation bubble formed over an airfoil. Exp. Fluids 59 (3), 52.CrossRefGoogle Scholar
Jaroslawski, T., Forte, M., Moschetta, J.-M., Delattre, G. & Gowree, E.R. 2022 Characterisation of boundary layer transition over a low Reynolds number rotor. Exp. Therm. Fluid Sci. 130, 110485.CrossRefGoogle Scholar
Jonáš, P., Mazur, O. & Uruba, V. 2000 On the receptivity of the by-pass transition to the length scale of the outer stream turbulence. Eur. J. Mech. (B/Fluids) 19 (5), 707–722.CrossRefGoogle Scholar
Jones, L.E., Sandberg, R.D. & Sandham, N.D. 2010 Stability and receptivity characteristics of a laminar separation bubble on an aerofoil. J. Fluid Mech. 648, 257–296.CrossRefGoogle Scholar
Kendall, J. 1998 Experiments on boundary-layer receptivity to freestream turbulence. AIAA Paper 98-0530.CrossRefGoogle Scholar
Klebanoff, P.S. & Tidstrom, K.D. 1972 Mechanism by which a two-dimensional roughness element induces boundary-layer transition. Phys. Fluids 15 (7), 1173–1188.CrossRefGoogle Scholar
Kurelek, J. 2021 The vortex dynamics of laminar separation bubbles. PhD thesis, University of Waterloo.Google Scholar
Kurelek, J.W., Kotsonis, M. & Yarusevych, S. 2018 Transition in a separation bubble under tonal and broadband acoustic excitation. J. Fluid Mech. 853, 1–36.CrossRefGoogle Scholar
Kurelek, J.W., Lambert, A.R. & Yarusevych, S. 2016 Coherent structures in the transition process of a laminar separation bubble. AIAA J. 54 (8), 2295–2309.CrossRefGoogle Scholar
Kurian, T. & Fransson, J.H.M. 2009 Grid-generated turbulence revisited. Fluid Dyn. Res. 41 (2), 021403.CrossRefGoogle Scholar
Li, H.J. & Yang, Z. 2019 Separated boundary layer transition under pressure gradient in the presence of free-stream turbulence. Phys. Fluids 31 (10), 104106.Google Scholar
Luchini, P. 2000 Reynolds-number-independent instability of the boundary layer over a flat surface: optimal perturbations. J. Fluid Mech. 404, 289–309.CrossRefGoogle Scholar
Lueptow, R.M., Breuer, K.S. & Haritonidis, J.H. 2004 Computer-aided calibration of X-probes using a look-up table. Exp. Fluids 6 (2), 115–118.CrossRefGoogle Scholar
Makita, H. & Sassa, K. 1991 Active turbulence generation in a laboratory wind tunnel. In Advances in Turbulence 3 (ed. A.V. Johansson & P.H. Alfredsson), pp. 497–505. Springer.CrossRefGoogle Scholar
Mamidala, S.B., Weingärtner, A. & Fransson, J.H.M. 2022 Leading-edge pressure gradient effect on boundary layer receptivity to free-stream turbulence. J. Fluid Mech. 935, A30.CrossRefGoogle Scholar
Marxen, O. & Henningson, D.S. 2011 The effect of small-amplitude convective disturbances on the size and bursting of a laminar separation bubble. J. Fluid Mech. 671, 1–33.CrossRefGoogle Scholar
Marxen, O., Kotapati, R.B., Mittal, R. & Zaki, T. 2015 Stability analysis of separated flows subject to control by zero-net-mass-flux jet. Phys. Fluids 27 (2), 024107.CrossRefGoogle Scholar
Marxen, O., Lang, M. & Rist, U. 2013 Vortex formation and vortex breakup in a laminar separation bubble. J. Fluid Mech. 728, 58–90.CrossRefGoogle Scholar
Marxen, O., Lang, M., Rist, U. & Wagner, S. 2003 A combined experimental/numerical study of unsteady phenomena in a laminar separation bubble. Flow Turbul. Combust. 71 (1–4), 133–146.CrossRefGoogle Scholar
Matsubara, M. & Alfredsson, P.H. 2001 Disturbance growth in boundary layers subjected to free-stream turbulence. J. Fluid Mech. 430, 149.CrossRefGoogle Scholar
Michelis, T., Yarusevych, S. & Kotsonis, M. 2017 Response of a laminar separation bubble to impulsive forcing. J. Fluid Mech. 820, 633–666.CrossRefGoogle Scholar
Morkovin, M.V. 1985 Bypass transition to turbulence and research desiderata. Trans. Turbines 2386, 161–204.Google Scholar
Nolan, K.P., Walsh, E.J. & McEligot, D.M. 2010 Quadrant analysis of a transitional boundary layer subject to free-stream turbulence. J. Fluid Mech. 658, 310.CrossRefGoogle Scholar
Olson, D.A., Katz, A.W., Naguib, A.M., Koochesfahani, M.M., Rizzetta, D.P. & Visbal, M.R. 2013 On the challenges in experimental characterization of flow separation over airfoils at low Reynolds number. Exp. Fluids 54 (2), 1–11.CrossRefGoogle Scholar
Ovchinnikov, V., Choudhari, M.M. & Piomelli, U. 2008 Numerical simulations of boundary-layer bypass transition due to high-amplitude free-stream turbulence. J. Fluid Mech. 613, 135–169.CrossRefGoogle Scholar
Pauley, L.L. 1994 Structure of local pressure-driven three-dimensional transient boundary-layer separation. AIAA J. 32 (5), 997–1005.CrossRefGoogle Scholar
Pauley, L.L., Moin, P. & Reynolds, W.C. 1990 The structure of two-dimensional separation. J. Fluid Mech. 220, 397–411.CrossRefGoogle Scholar
Rist, U. & Maucher, U. 2002 Investigations of time-growing instabilities in laminar separation bubbles. Eur. J. Mech. (B/Fluids) 21 (5), 495–509.CrossRefGoogle Scholar
Rodríguez, D. & Gennaro, E.M. 2019 Enhancement of disturbance wave amplification due to the intrinsic three-dimensionalisation of laminar separation bubbles. Aeronaut. J. 123 (1268), 1492–1507.CrossRefGoogle Scholar
Rodríguez, D., Gennaro, E.M. & Juniper, M.P. 2013 The two classes of primary modal instability in laminar separation bubbles. J. Fluid Mech. 734, R4.CrossRefGoogle Scholar
Rodríguez, D., Gennaro, E.M. & Souza, L.F. 2021 Self-excited primary and secondary instability of laminar separation bubbles. J. Fluid Mech. 906, A13.CrossRefGoogle Scholar
Rodríguez, D. & Theofilis, V. 2010 Structural changes of laminar separation bubbles induced by global linear instability. J. Fluid Mech. 655, 280–305.CrossRefGoogle Scholar
Schmid, P.J. & Henningson, D.S. 2000 Stability and Transition in Shear Flows, vol. 142. Springer Science & Business Media.Google Scholar
Serna, J. & Lázaro, B.J. 2014 The final stages of transition and the reattachment region in transitional separation bubbles. Exp. Fluids 55 (4), 1–17.CrossRefGoogle Scholar
Simoni, D., Lengani, D., Ubaldi, M., Zunino, P. & Dellacasagrande, M. 2017 Inspection of the dynamic properties of laminar separation bubbles: free-stream turbulence intensity effects for different Reynolds numbers. Exp. Fluids 58 (6), 66.CrossRefGoogle Scholar
Studer, G., Arnal, D., Houdeville, R. & Seraudie, A. 2006 Laminar–turbulent transition in oscillating boundary layer: experimental and numerical analysis using continuous wavelet transform. Exp. Fluids 41 (5), 685–698.CrossRefGoogle Scholar
Veerasamy, D., Atkin, C.J. & Ponnusami, S.A. 2021 Aerofoil wake-induced transition characteristics on a flat-plate boundary layer. J. Fluid Mech. 920, A29.CrossRefGoogle Scholar
Verdoya, J., Dellacasagrande, M., Lengani, D., Simoni, D. & Ubaldi, M. 2021 Inspection of structures interaction in laminar separation bubbles with extended proper orthogonal decomposition applied to multi-plane particle image velocimetry data. Phys. Fluids 33 (4), 043607.CrossRefGoogle Scholar
Volino, R.J. 1998 A new model for free-stream turbulence effects on boundary layers. ASME. J. Turbomach. 120 (3), 613–620.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
Westin, K.J.A., Boiko, A.V., Klingmann, B.G.B., Kozlov, V.V. & Alfredsson, P.H. 1994 Experiments in a boundary layer subjected to free stream turbulence. Part 1. Boundary layer structure and receptivity. J. Fluid Mech. 281, 193–218.CrossRefGoogle Scholar
Wissink, J.G. & Rodi, W. 2006 Direct numerical simulations of transitional flow in turbomachinery. J. Turbomach. 128 (4), 668–667.CrossRefGoogle Scholar
Xu, D. & Wu, X. 2021 Elevated low-frequency free-stream vortical disturbances eliminate boundary-layer separation. J. Fluid Mech. 920, A14.CrossRefGoogle Scholar
Xu, H., Mughal, S.M., Gowree, E.R., Atkin, C.J. & Sherwin, S.J. 2017 Destabilisation and modification of Tollmien–Schlichting disturbances by a three-dimensional surface indentation. J. Fluid Mech. 819, 592–620.CrossRefGoogle Scholar
Yarusevych, S. & Kotsonis, M. 2017 Steady and transient response of a laminar separation bubble to controlled disturbances. J. Fluid Mech. 813, 955–990.CrossRefGoogle 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 conditions. J. Fluid Mech. 202, 403–442.CrossRefGoogle Scholar