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{Doohan:2022:10.1017/jfm.2022.686,
author = {Doohan, P and Bengana, Y and Yang, Q and Willis, A and Hwang, Y},
doi = {10.1017/jfm.2022.686},
journal = {Journal of Fluid Mechanics},
pages = {1--36},
title = {The state space and travelling-wave solutions in two-scale wall-bounded turbulence},
url = {http://dx.doi.org/10.1017/jfm.2022.686},
volume = {947},
year = {2022}
}
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RIS format (EndNote, RefMan)

TY  - JOUR
AB  - The computation of invariant solutions and the visualisation of the associated state spacehave played a key role in the understanding of transition and the self-sustaining processin wall-bounded shear flows. In this study, an extension of this approach is sought for aturbulent flow which explicitly exhibits multi-scale behaviour. The minimal unit of multiscale near-wall turbulence, which resolves two adjacent spanwise integral length scalesof motion, is considered using a shear stress-driven flow model (Doohan et al., J. FluidMech., vol. 913, 2021, A8). The edge state, twenty-six travelling waves and two periodicorbits are computed, which represent either the large- or small-scale self-sustainingprocesses. Given that the spanwise length scales are not widely separated here, it could beenvisaged that turbulent trajectories visit these solutions in the state space. Consideringthe intra- and inter-scale dynamics of the flow, numerous phase portraits are examined,but the turbulent state is not found to approach any of these solutions. A detailedanalysis reveals that this is due to the lack of scale interaction processes captured bythe invariant solutions, including the mean-fluctuation interaction, the energy cascade inthe streamwise wavenumber space and the cascade-driven energy production discoveredrecently. There is a single solution that resembles turbulence much more than the others,which captures two-scale energetics and a scale interaction process involving energyfeeding from small to large spanwise scales through the subharmonic sinuous streakinstability mode. Based on these observations, it is conjectured that the state space viewof turbulent trajectories wandering between solutions would need suitable refinement tomodel multi-scale turbulence, when each solution does not represent multi-scale processesof turbulence. In particular, invariant solutions that are inherently multi-scale would berequired.
AU  - Doohan,P
AU  - Bengana,Y
AU  - Yang,Q
AU  - Willis,A
AU  - Hwang,Y
DO  - 10.1017/jfm.2022.686
EP  - 36
PY  - 2022///
SN  - 0022-1120
SP  - 1
TI  - The state space and travelling-wave solutions in two-scale wall-bounded turbulence
T2  - Journal of Fluid Mechanics
UR  - http://dx.doi.org/10.1017/jfm.2022.686
UR  - https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/state-space-and-travellingwave-solutions-in-twoscale-wallbounded-turbulence/3C40F9D2F776778BF2C61CB6AADD21C7
UR  - http://hdl.handle.net/10044/1/99003
VL  - 947
ER  -
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