Imperial College London
Alternate

Dr. Yongyun Hwang

Faculty of Engineering, Department of Aeronautics

Reader in Fluid Mechanics
 
 
 
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Contact

 

+44 (0)20 7594 5078y.hwang

 
 
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Location

 

337City and Guilds BuildingSouth Kensington Campus

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Summary

 

Publications

Citation

BibTex format

@article{de:2016:10.1017/jfm.2016.665,
author = {de, Giovanetti M and Hwang, Y and Choi, H},
doi = {10.1017/jfm.2016.665},
journal = {Journal of Fluid Mechanics},
pages = {511--538},
title = {Skin-friction generation by attached eddies in turbulent channel flow},
url = {http://dx.doi.org/10.1017/jfm.2016.665},
volume = {808},
year = {2016}
}
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RIS format (EndNote, RefMan)

TY  - JOUR
AB  - Despite a growing body of recent evidence on the hierarchical organization of the selfsimilarenergy-containing motions in the form of Townsend’s attached eddies in wallboundedturbulent flows, their role in turbulent skin-friction generation is currentlyknown very little. In this paper, the contribution of each of these self-similar energycontainingmotions to turbulent skin friction is explored up to Reτ  4000. Threedifferent approaches are employed to quantify the skin-friction generation by the motions,the spanwise length scale of which is smaller than a given cut-off wavelength: 1) FIKidentity in combination with the spanwise wavenumber spectra of the Reynolds shearstress; 2) confinement of the spanwise computational domain; 3) artificial damping ofthe motions to be examined. The near-wall motions are found to continuously lose theirrole in skin-friction generation on increasing the Reynolds number, consistent with theprevious finding at low Reynolds numbers. The largest structures given in the form ofvery-large-scale and large-scale motions are also found to be of limited importance: dueto a non-trivial scale-interaction process, their complete removal yields only 5 ∼ 8% ofskin-friction reduction at all the Reynolds numbers considered, although they are foundto be responsible for 20 ∼ 30% of total skin friction at Reτ  2000. Application of all thethree approaches consistently reveals that the largest amount of skin friction is generatedby the self-similar motions populating the logarithmic region. It is further shown thatthe contribution of these motions to turbulent skin friction gradually increases with theReynolds number, and that these coherent structures are eventually responsible for mostof turbulent skin-friction generation at sufficiently high Reynolds numbers.
AU  - de,Giovanetti M
AU  - Hwang,Y
AU  - Choi,H
DO  - 10.1017/jfm.2016.665
EP  - 538
PY  - 2016///
SN  - 1469-7645
SP  - 511
TI  - Skin-friction generation by attached eddies in turbulent channel flow
T2  - Journal of Fluid Mechanics
UR  - http://dx.doi.org/10.1017/jfm.2016.665
UR  - https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/skinfriction-generation-by-attached-eddies-in-turbulent-channel-flow/41EACC90D8139214012C7FD1F26E4969
UR  - http://hdl.handle.net/10044/1/41313
VL  - 808
ER  -
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