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{Hwang:2021:10.1017/jfm.2021.1057,
author = {Hwang, Y and Hutchins, N and Marusic, I},
doi = {10.1017/jfm.2021.1057},
journal = {Journal of Fluid Mechanics},
pages = {1--24},
title = {The logarithmic variance of streamwise velocity and k−1 conundrum in wall turbulence},
url = {http://dx.doi.org/10.1017/jfm.2021.1057},
volume = {933},
year = {2021}
}
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RIS format (EndNote, RefMan)

TY  - JOUR
AB  - The logarithmic dependence of streamwise turbulence intensity has repeatedly beenobserved in recent experimental and direct numerical simulation data. However, itsspectral counterpart, a well-developed k−1spectrum (k is the spatial wavenumber ina wall-parallel direction), has not been convincingly observed from the same data. Inthe present study, we revisit the spectrum-based attached eddy model of Perry andco-workers, who proposed the emergence of k−1spectrum in the inviscid limit, forsmall but finite z/δ and for finite Reynolds numbers (z is the wall-normal co-ordinateand δ the outer length scale). In the upper logarithmic layer (or inertial sublayer),a reexamination reveals that the intensity of the spectrum must vary with the wallnormal location at order of z/δ, consistent with the early observation argued with‘incomplete similarity’. The streamwise turbulence intensity is subsequently calculated,demonstrating that the existence of a well-developed k−1spectrum is not a necessarycondition for the approximate logarithmic wall-normal dependence of turbulence intensity– a more general condition is the existence of pre-multiplied power-spectral intensity ofO(1) for O(1/δ) < k < O(1/z). Furthermore, it is shown that the Townsend-Perryconstant must weakly be dependent on the Reynolds number. Finally, the analysis issemi-empirically extended to the lower logarithmic layer (or mesolayer), and a near-wallcorrection for the turbulence intensity is subsequently proposed. All the predictions ofthe proposed model and the related analyses/assumptions are validated with high-fidelityexperimental data (Samie et al., J. Fluid Mech., 2018, vol. 851, pp. 391–415).
AU  - Hwang,Y
AU  - Hutchins,N
AU  - Marusic,I
DO  - 10.1017/jfm.2021.1057
EP  - 24
PY  - 2021///
SN  - 0022-1120
SP  - 1
TI  - The logarithmic variance of streamwise velocity and k−1 conundrum in wall turbulence
T2  - Journal of Fluid Mechanics
UR  - http://dx.doi.org/10.1017/jfm.2021.1057
UR  - https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/logarithmic-variance-of-streamwise-velocity-and-k1-conundrum-in-wall-turbulence/1EF3B223C23015595222D8454FC483CA
UR  - http://hdl.handle.net/10044/1/93137
VL  - 933
ER  -
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