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:2022:10.1017/jfm.2022.499,
author = {Hernandez, C and Yang, Q and Hwang, Y},
doi = {10.1017/jfm.2022.499},
journal = {Journal of Fluid Mechanics},
title = {Generalised quasilinear approximations of turbulent channel flow: Part 2. Spanwise triadic scale interactions},
url = {http://dx.doi.org/10.1017/jfm.2022.499},
volume = {944},
year = {2022}
}
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RIS format (EndNote, RefMan)

TY  - JOUR
AB  - Continuing from Part 1 (Hernández et al., J. Fluid Mech., vol. 936, A33, 2022), a generalized quasilinear (GQL) approximation is studied in turbulent channel flow using a flow decomposition defined with spanwise Fourier modes: the flow is decomposed into a set of low-wavenumber spanwise Fourier modes and the rest high-wavenumber modes. This decomposition leads to the nonlinear low-wavenumber group that supports the self-sustaining process within the given integral length scales, whereas the linearised high-wave number group is not able to do so, unlike the GQL models in Part 1 which place a minimal mathematical description for the self-sustaining process across all integral scales. Despite the important physical difference, it is shown that the GQL models in this study share some similarities with those in Part 1: i.e. the reduced multi-scale behaviour and anisotropic turbulent fluctuations. Furthermore, despite not being able to support the self-sustaining process in the high-wavenumber group, the GQL models in the present study are found to reproduce some key statistical features in the high-wavenumber group solely through the ‘scattering’ mechanism proposed by previous studies. Finally, using the nature of the GQL approximation, a set of numerical experiments suppressing certain triadic nonlinear interactions are further carried out. This unveils some key roles played by the certain types of triadic interactions including energy cascade and inverse energytransfer in the near-wall region. In particular, the inhibition of inverse energy transfer in the spanwise direction leads to suppression of the near-wall positive turbulent transport at large scales.
AU  - Hernandez,C
AU  - Yang,Q
AU  - Hwang,Y
DO  - 10.1017/jfm.2022.499
PY  - 2022///
SN  - 0022-1120
TI  - Generalised quasilinear approximations of turbulent channel flow: Part 2. Spanwise triadic scale interactions
T2  - Journal of Fluid Mechanics
UR  - http://dx.doi.org/10.1017/jfm.2022.499
UR  - https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/abs/generalised-quasilinear-approximations-of-turbulent-channel-flow-part-2-spanwise-triadic-scale-interactions/4568DE57740CE87CF28CCC00DB12FDD9
UR  - http://hdl.handle.net/10044/1/97805
VL  - 944
ER  -
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