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Boundary layer stabilization using free-stream vortices

  • L. Siconolfi (a1), S. Camarri (a1) and J. H. M. Fransson (a2)

Abstract

In this numerical investigation we explore the possibility of applying free-stream vortices as a passive flow control method for delaying the transition to turbulence. The work is motivated by previous experimental studies demonstrating that stable streamwise boundary layer (BL) streaks can attenuate both two- and three-dimensional disturbances inside the BL, leading to transition delay, with the implication of reducing skin-friction drag. To date, successful control has been obtained using physical BL modulators mounted on the surface in order to generate stable streaks. However, surface mounted BL modulators are doomed to failure when the BL is subject to free-stream turbulence (FST), since a destructive interaction between the two is inevitable. In order to tackle free-stream disturbances, such as FST, a smooth surface is desired, which has motivated us to seek new methods to induce streamwise streaks inside the BL. A first step, in a systematic order, is taken in the present paper to prove the control idea of generating free-stream vortices for the attenuation of ordinary Tollmien–Schlichting waves inside the BL. In this proof-of-concept study we show that, by applying a spanwise array of counter-rotating free-stream vortices, inducing streamwise BL streaks further downstream, it is possible to alter the BL stability characteristics to such a degree that transition delay may be accomplished. For the demonstration we use direct numerical simulations along with stability analysis.

Copyright

Corresponding author

Email address for correspondence: jens.fransson@mech.kth.se

References

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Andersson, P., Brandt, L., Bottaro, A. & Henningson, D. S. 2001 On the breakdown of boundary layer streaks. J. Fluid Mech. 428, 2960.
Bagheri, S. & Hanifi, A. 2007 The stabilizing effect of streaks on TS and oblique waves: a parametric study. Phys. Fluids 19, 078103.
Batchelor, G. K. 1964 Axial flow in trailing line vortices. J. Fluid Mech. 20, 645658.
Camarri, S., Fransson, J. H. M. & Talamelli, A. 2013 Numerical investigation of the Afrodite transition control strategy. In Progress in Turbulence V (ed. Talamelli, A., Oberlack, M. & Peinke, J.), pp. 6569. Springer.
Cossu, C. & Brandt, L. 2002 Stabilization of Tollmien–Schlichting waves by finite amplitude optimal streaks in the Blasius boundary layer. Phys. Fluids 14, L57L60.
Cossu, C. & Brandt, L. 2004 On Tollmien–Schlichting-like waves in streaky boundary layers. Eur. J. Mech. (B/Fluids) 23, 815833.
Fransson, J. H. M., Brandt, L., Talamelli, A. & Cossu, C. 2004 Experimental and theoretical investigation of the nonmodal growth of steady streaks in a flat plate boundary layer. Phys. Fluids 16 (10), 36273638.
Fransson, J. H. M., Brandt, L., Talamelli, A. & Cossu, C. 2005 Experimental study of the stabilisation of Tollmien–Schlichting waves by finite amplitude streaks. Phys. Fluids 17, 054110.
Fransson, J. H. M. & Talamelli, A. 2012 On the generation of steady streamwise streaks in flat-plate boundary layers. J. Fluid Mech. 698, 211234.
Fransson, J. H. M., Talamelli, A., Brandt, L. & Cossu, C. 2006 Delaying transition to turbulence by a passive mechanism. Phys. Rev. Lett. 96, 064501.
Kachanov, Y. S. & Tararykin, O. I. 1987 Experimental investigation of a relaxing boundary layer. Proc. Siberian Div. USSR Acad. Sci., Ser. Tech. Sci. 18 (5), 919 (in Russian).
Landahl, M. T. 1980 A note on an algebraic instability of inviscid parallel shear flows. J. Fluid Mech. 98, 243251.
Piot, E., Casalis, G. & Rist, U. 2008 Stability of the laminar boundary layer flow encountering a row of roughness elements: biglobal stability approach and DNS. Eur. J. Mech. B 27, 684706.
Sattarzadeh, S. S., Fransson, J. H. M., Talamelli, A. & Fallenius, B. E. G. 2014 Consecutive turbulence transition delay with reinforced passive control. Phys. Rev. E 89, 061001(R).
Shahinfar, S., Fransson, J. H. M., Sattarzadeh, S. S. & Talamelli, A. 2013 Scaling of streamwise boundary layer streaks and their ability to reduce skin-friction drag. J. Fluid Mech. 733, 132.
Shahinfar, S., Sattarzadeh, S. S. & Fransson, J. H. M. 2014 Passive boundary layer control of oblique disturbances by finite-amplitude streaks. J. Fluid Mech. 749, 136.
Shahinfar, S., Sattarzadeh, S. S., Fransson, J. H. M. & Talamelli, A. 2012 Revival of classical vortex generators now for transition delay. Phys. Rev. Lett. 109, 074501.
Tani, I. & Komoda, H. 1962 Boundary layer transition in the presence of streamwise vortices. J. Aero. Sci. 29, 440444.
Velte, C. M., Hansen, M. O. L. & Okulov, V. L. 2008 Helical structure of longitudinal vortices embedded in turbulent wall-bounded flow. J. Fluid Mech. 619, 167177.
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Boundary layer stabilization using free-stream vortices

  • L. Siconolfi (a1), S. Camarri (a1) and J. H. M. Fransson (a2)

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