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Rouhi, A. 
ORCID: 0000-0002-7837-418X, Fu, M.K., Chandran, D., Zampiron, A., Smits, A.J. and Marusic, I.,
2023.
Turbulent drag reduction by spanwise wall forcing. Part 1. Large-eddy simulations.
Journal of Fluid Mechanics, 968: A6.
ISSN 0022-1120
Abstract
Turbulent drag reduction (DR) through streamwise travelling waves of the spanwise wall oscillation is investigated over a wide range of Reynolds numbers. Here, in Part 1, wall-resolved large-eddy simulations in a channel flow are conducted to examine how the frequency and wavenumber of the travelling wave influence the DR at friction Reynolds numbers Reτ=951 and 4000. The actuation parameter space is restricted to the inner-scaled actuation (ISA) pathway, where DR is achieved through direct attenuation of the near-wall scales. The level of turbulence attenuation, hence DR, is found to change with the near-wall Stokes layer protrusion height ℓ0.01. A range of frequencies is identified where the Stokes layer attenuates turbulence, lifting up the cycle of turbulence generation and thickening the viscous sublayer; in this range, the DR increases as ℓ0.01 increases up to 30 viscous units. Outside this range, the strong Stokes shear strain enhances near-wall turbulence generation leading to a drop in DR with increasing ℓ0.01. We further find that, within our parameter and Reynolds number space, the ISA pathway has a power cost that always exceeds any DR savings. This motivates the study of the outer-scaled actuation pathway in Part 2, where DR is achieved through actuating the outer-scaled motions.
| Item Type: | Journal article | ||||||
|---|---|---|---|---|---|---|---|
| Publication Title: | Journal of Fluid Mechanics | ||||||
| Creators: | Rouhi, A., Fu, M.K., Chandran, D., Zampiron, A., Smits, A.J. and Marusic, I. | ||||||
| Publisher: | Cambridge University Press | ||||||
| Date: | 2023 | ||||||
| Volume: | 968 | ||||||
| ISSN: | 0022-1120 | ||||||
| Identifiers: |
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| Rights: | This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0), which permits unrestricted re-use, distribution and reproduction, provided the original article is properly cited. | ||||||
| Divisions: | Schools > School of Science and Technology | ||||||
| Record created by: | Jonathan Gallacher | ||||||
| Date Added: | 07 Aug 2023 07:46 | ||||||
| Last Modified: | 07 Aug 2023 08:09 | ||||||
| URI: | https://irep.ntu.ac.uk/id/eprint/49504 |
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