Turbulent drag reduction by spanwise wall forcing. Part 1. Large-eddy simulations

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Rouhi, A ORCID: https://orcid.org/0000-0002-7837-418X, Fu, MK, Chandran, D, Zampiron, A, Smits, AJ 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

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Official URL: https://doi.org/10.1017/jfm.2023.499

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:	Number Type 10.1017/jfm.2023.499 DOI 1787823 Other
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