Abstract
This paper reports the modifications of near-wall low-speed streaks by local surface oscillations generated by a spanwise-aligned actuator array in a turbulent boundary layer over a flat plate at Re θ = 1,000. The streaks were educed from PIV-measured fluctuating velocities in the viscous sublayer using a procedure proposed by Schoppa and Hussain (2002). The wall-based perturbations, corresponding to a large skin-friction drag reduction (about 50 % at 17 wall units downstream of the actuator array), modified greatly the low-speed streaks, leading to a reduction by over 15 % in both the averaged width and spacing while an increase by 17 % in the streak center number. The alterations of velocity streak distributions are consistent with results from other techniques such as smoke-wire flow visualization and two-point cross-correlation, where the breakup of large-scale coherent structures into small-scale ones was observed.
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Bai HL, Zhou Y, Zhang WG, Xu SJ et al (2012) Active control of turbulent boundary layer based on local surface perturbation. J Fluid Mech (submitted)
Du Y, Symeonidis V, Karniadakis GE (2002) Drag reduction in wall-bounded turbulence via a transverse travelling wave. J Fluid Mech 457:1–34
Schoppa W, Hussain F (2002) Coherent structure generation in near-wall turbulence. J Fluid Mech 453:57–108
Acknowledgments
This work is supported by grants PolyU 5329/11E (HKSAR) and 11172085 (NSFC).
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© 2014 Springer-Verlag Berlin Heidelberg
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Bai, H.L., Zhou, Y., Zhang, W.G. (2014). Streaky Structures in a Controlled Turbulent Boundary Layer. In: Zhou, Y., Liu, Y., Huang, L., Hodges, D. (eds) Fluid-Structure-Sound Interactions and Control. Lecture Notes in Mechanical Engineering. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-40371-2_19
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DOI: https://doi.org/10.1007/978-3-642-40371-2_19
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Online ISBN: 978-3-642-40371-2
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