Description
Vortex organization in the outer layer of a turbulent boundary layer overlying sparse, hemispherical roughness elements is explored with two-component particle-image velocimetry (PIV) in multiple streamwise-wall-normal measurement planes downstream and between elements. The presence of sparse roughness elements causes a shortening of the streamwise length scale in the near-wall region. These measurements confirm that vortex packets exist in the outer layer of flow over rough walls, but that their organization is altered, and this is interpreted as the underlying cause of the length-scale reduction. In particular, the elements shed vortices which appear to align in the near-wall region, but are distinct from the packets. Further, it is observed that ejection events triggered in the element wakes are more intense compared to the ejection events in smooth wall. We speculate that this may initiate a self-sustaining mechanism leading to the formation of hairpin packets as a much more effective instability compared to those typical of smooth-wall turbulence.
Details
Title
- Vortex organization in a turbulent boundary layer overlying sparse roughness elements
Contributors
- Guala, Michael (Author)
- Tomkins, Christopher D. (Author)
- Christensen, Kenneth T. (Author)
- Adrian, Ronald (Author)
- Ira A. Fulton Schools of Engineering (Contributor)
- School for the Engineering of Matter, Transport and Energy (Contributor)
Date Created
The date the item was original created (prior to any relationship with the ASU Digital Repositories.)
2012-09-09
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Identifier
- Digital object identifier: 10.1080/00221686.2012.729229
- Identifier TypeInternational standard serial numberIdentifier Value0022-1686
- Identifier TypeInternational standard serial numberIdentifier Value1814-2079
Note
- This is an Author's Accepted Manuscript of an article published as Michele Guala , Christopher D. Tomkins , Kenneth T. Christensen , Ronald J. Adrian. (2012) Vortex organization in a turbulent boundary layer overlying sparse roughness elements, Journal of Hydraulic Research, 50(5), 465-481 http://dx.doi.org/10.1080/00221686.2012.729229, opens in a new window Copyright Taylor & Francis, available online at: http://www.tandfonline.com/doi/abs/10.1080/00221686.2012.729229, opens in a new window
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Michele Guala , Christopher D. Tomkins , Kenneth T. Christensen , Ronald J. Adrian. (2012) Vortex organization in a turbulent boundary layer overlying sparse roughness elements, Journal of Hydraulic Research, 50(5), 465-481 http://dx.doi.org/10.1080/00221686.2012.729229