Journal article
Reorganisation of turbulence by large and spanwise-varying riblets
S Endrikat, R Newton, D Modesti, R García-Mayoral, N Hutchins, D Chung
Journal of Fluid Mechanics | Cambridge University Press | Published : 2022
DOI: 10.1017/jfm.2022.897
Abstract
We study the flow above non-optimal riblets, specifically large drag-increasing and two-scale trapezoidal riblets. In order to reach large Reynolds numbers and large scale separation while retaining access to flow details, we employ a combination of boundary-layer hot-wire measurements and direct numerical simulation (DNS) in minimal-span channels. Although the outer Reynolds numbers differ, we observe fair agreement between experiments and DNS at matched viscous-friction-scaled riblet spacings in the overlapping physical and spectral regions, providing confidence that both data sets are valid. We find that hot-wire velocity spectra above very large riblets with are depleted of near-wall ene..
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Grants
Awarded by Air Force Office of Scientific Research
Funding Acknowledgements
The authors gratefully acknowledge the support of the Australian Research Council Discovery Project DP170102595. This material is based upon work supported by the Air Force Office of Scientific Research under award number FA2386-21-1-4018 (program manager: Ryan Carr, AOARD). We also thank Doug Smith (EOARD). This research is undertaken with the assistance of computational resources from NCI that is supported by the Australian Government and from Pawsey that is funded by the Australian Government and the Government of Western Australia. S. E. was partially funded through the `Melbourne School or Engineering Write-Up Award.'