Journal article
Effect of the dynamic slip boundary condition on the near-wall turbulent boundary layer
Journal of fluid mechanics, Vol.901, A11
10/25/2020
DOI: 10.1017/jfm.2020.514
Abstract
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 ($Re_\theta$) 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.
Details
- Title: Subtitle
- Effect of the dynamic slip boundary condition on the near-wall turbulent boundary layer
- Creators
- Cong Wang - California Institute of TechnologyMorteza Gharib - California Institute of Technology
- Resource Type
- Journal article
- Publication Details
- Journal of fluid mechanics, Vol.901, A11
- Publisher
- Cambridge University Press
- DOI
- 10.1017/jfm.2020.514
- ISSN
- 0022-1120
- eISSN
- 1469-7645
- Number of pages
- 32
- Language
- English
- Date published
- 10/25/2020
- Academic Unit
- Mechanical Engineering
- Record Identifier
- 9984446451302771
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