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{Hernandez:2020:10.1017/jfm.2020.678,
author = {Hernandez, C and Hwang, Y},
doi = {10.1017/jfm.2020.678},
journal = {Journal of Fluid Mechanics},
pages = {A11--1--A11--26},
title = {Spectral energetics of a quasilinear approximation in uniform shear turbulence},
url = {http://dx.doi.org/10.1017/jfm.2020.678},
volume = {604},
year = {2020}
}
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RIS format (EndNote, RefMan)

TY  - JOUR
AB  - The spectral energetics of a quasilinear (QL) model is studied in uniform shear turbulence. For the QL approximation, the velocity is decomposed into a mean averaged in the streamwise direction and the remaining fluctuation. The equations for the meanare fully considered, while the equations for the fluctuation are linearised around the mean. The QL model exhibits an energy cascade in the spanwise direction, but this is mediated by highly anisotropic small-scale motions unlike that in direct numerical simulation mediated by isotropic motions. In the streamwise direction, the energy cascadeis shown to be completely inhibited in the QL model, resulting in highly elevated spectral energy intensity residing only at the streamwise integral length scales. It is also found that the streamwise wave number spectra of turbulent transport, obtained with the classical Reynolds decomposition, statistically characterizes the instability of the linearised fluctuation equations. Further supporting evidence of this claim is presented by carrying out a numerical experiment, in which the QL model with single streamwise Fourier mode is found to generate the strongest turbulence for Lx/Lz= 1∼3, consistent with previous findings (Lx and Lz are the streamwise and spanwise computational domains, respectively). Finally, the QL model is shown to completely ignore the role of slow pressure in the fluctuations, resulting in a significant damage of pressure-strain transport at all length scales. This explains the anisotropic turbulence of the QL model throughout the entire wavenumber space as well as the inhibited nonlinear regeneration of streamwise vortices in the self-sustaining process.
AU  - Hernandez,C
AU  - Hwang,Y
DO  - 10.1017/jfm.2020.678
EP  - 1
PY  - 2020///
SN  - 0022-1120
SP  - 11
TI  - Spectral energetics of a quasilinear approximation in uniform shear turbulence
T2  - Journal of Fluid Mechanics
UR  - http://dx.doi.org/10.1017/jfm.2020.678
UR  - https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/spectral-energetics-of-a-quasilinear-approximation-in-uniform-shear-turbulence/8B2A4CC37BCE43FC98209CD2E67FA07E
UR  - http://hdl.handle.net/10044/1/82218
VL  - 604
ER  -
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