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Effect of the dynamic slip boundary condition on the near-wall turbulent boundary layer

Wang, Cong and Gharib, Morteza (2020) Effect of the dynamic slip boundary condition on the near-wall turbulent boundary layer. Journal of Fluid Mechanics, 901 . Art. No. A11. ISSN 0022-1120. doi:10.1017/jfm.2020.514.

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The manipulation of near-wall turbulent structures in a turbulent boundary layer (TBL) is an effective way to reduce the turbulent frictional drag. This paper demonstrates the effectiveness of a novel approach for the manipulation of near-wall structures in a TBL with Reynolds number (R_eθ) set to 1200. The manipulation is achieved by employing a sustainable wall-attached air-film array. The static and dynamic interface configuration of the air film can be modulated, which generates a dynamic slip boundary condition. For modulation frequencies within the TBL receptivity, this approach shows that it can effectively modify the TBL near-wall velocity/vorticity field. For a typical modulation frequency of 50 Hz, the near-wall mean streamwise velocity decreases and the wall-normal velocity increases when compared to the canonical flat plate TBL. The mean transverse vorticity is suppressed in the near-wall region and its peak is ‘pushed’ outward away from the wall. In the vicinity of modulated air-film array, the phase-locked velocity/vorticity field demonstrates harmonic motions such as a Stokes-type oscillatory motion. The distribution of shear stresses indicates suppressed momentum transfer toward the wall. Estimation of the wall skin friction via the Clauser chart method indicates a reduction of the wall skin friction up to 40 % in the downstream region of the air-film array. A control volume analysis shows that the TBL gains a significant amount of momentum over the oscillating air films, which suggests that the oscillating air film acts like a source of momentum. This pumping effect could potentially explain the observed wall skin friction reduction effect.

Item Type:Article
Related URLs:
URLURL TypeDescription
Wang, Cong0000-0002-8271-5637
Gharib, Morteza0000-0003-0754-4193
Additional Information:© The Author(s), 2020. Published by Cambridge University Press. Received 3 November 2019; revised 11 May 2020; accepted 13 June 2020. Published online by Cambridge University Press: 24 August 2020. This work was supported by the Office of Naval Research under grant no. N00014-15-1-2479. C.W. was supported by the Stanback fellowship at GALCIT, Caltech. The authors appreciate the communication and discussion with Professor G.L. Brown. The authors report no conflict of interest.
Funding AgencyGrant Number
Office of Naval Research (ONR)N00014-15-1-2479
Subject Keywords:turbulence control, turbulent boundary layers, drag reduction
Record Number:CaltechAUTHORS:20200917-145619942
Persistent URL:
Official Citation:Wang, C., & Gharib, M. (2020). Effect of the dynamic slip boundary condition on the near-wall turbulent boundary layer. Journal of Fluid Mechanics, 901, A11. doi:10.1017/jfm.2020.514
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:105437
Deposited By: Tony Diaz
Deposited On:17 Sep 2020 23:37
Last Modified:16 Nov 2021 18:43

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