An energy-efficient pathway to turbulent drag reduction
Abstract
Simulations and experiments at low Reynolds numbers have suggested that skin-friction drag generated by turbulent fluid flow over a surface can be decreased by oscillatory motion in the surface, with the amount of drag reduction predicted to decline with increasing Reynolds number. Here, we report direct measurements of substantial drag reduction achieved by using spanwise surface oscillations at high friction Reynolds numbers (Re_τ) up to 12,800. The drag reduction occurs via two distinct physical pathways. The first pathway, as studied previously, involves actuating the surface at frequencies comparable to those of the small-scale eddies that dominate turbulence near the surface. We show that this strategy leads to drag reduction levels up to 25% at Re_τ = 6,000, but with a power cost that exceeds any drag-reduction savings. The second pathway is new, and it involves actuation at frequencies comparable to those of the large-scale eddies farther from the surface. This alternate pathway produces drag reduction of 13% at Re_τ = 12,800. It requires significantly less power and the drag reduction grows with Reynolds number, thereby opening up potential new avenues for reducing fuel consumption by transport vehicles and increasing power generation by wind turbines.
Additional Information
© The Author(s) 2021. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. Received 25 March 2021; Accepted 09 September 2021; Published 04 October 2021. The research was funded through the Deep Science Fund of Intellectual Ventures. We thank the Scientific Instrument Manufacturing and Test Group at Intellectual Ventures Laboratory for the fabrication of SATB, and Wayt Gibbs for the review of the paper and helpful comments. Computing resources were provided through the Spartan High-Performance Computing service at The University of Melbourne, the Pawsey Supercomputing Centre, and the National Computing Infrastructure (NCI) programme with funding from the Australian Government and the Government of Western Australia. Data availability: The datasets generated during the current study are available in the University of Melbourne Figshare repository, https://doi.org/10.26188/1655706038. Code availability: The code to support the findings in this work is available upon request from the authors. Author Contributions: All authors contributed to the writing of the paper and in shaping the results and conclusions. I.M. and A.J.S. conceived the original ideas and contributed to all aspects of the work; D.C. and M.K.F. lead the experimental studies; D.W. and B.H. lead the design and development of the SATB; and A.R. and D.C. lead the numerical studies. The authors declare no competing interests. Peer review information: Nature Communications thanks the anonymous reviewer(s) for their contribution to the peer review of this work.Attached Files
Published - s41467-021-26128-8.pdf
Supplemental Material - 41467_2021_26128_MOESM1_ESM.pdf
Supplemental Material - 41467_2021_26128_MOESM2_ESM.docx
Supplemental Material - 41467_2021_26128_MOESM3_ESM.mp4
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Additional details
- Eprint ID
- 111177
- Resolver ID
- CaltechAUTHORS:20211004-200124074
- Intellectual Ventures
- Australian Government
- Government of Western Australia
- Created
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2021-10-04Created from EPrint's datestamp field
- Updated
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2021-10-04Created from EPrint's last_modified field
- Caltech groups
- GALCIT