Coupling between free-surface fluctuations, velocity fluctuations and turbulent Reynolds stresses during the upstream propagation of positive surges, bores and compression waves

Leng, Xinqian and Chanson, Hubert (2016) Coupling between free-surface fluctuations, velocity fluctuations and turbulent Reynolds stresses during the upstream propagation of positive surges, bores and compression waves. Environmental Fluid Mechanics, 16 4: 695-719. doi:10.1007/s10652-015-9438-8

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Author Leng, Xinqian
Chanson, Hubert
Title Coupling between free-surface fluctuations, velocity fluctuations and turbulent Reynolds stresses during the upstream propagation of positive surges, bores and compression waves
Journal name Environmental Fluid Mechanics   Check publisher's open access policy
ISSN 1573-1510
1567-7419
Publication date 2016-08
Year available 2015
Sub-type Article (original research)
DOI 10.1007/s10652-015-9438-8
Open Access Status File (Author Post-print)
Volume 16
Issue 4
Start page 695
End page 719
Total pages 25
Place of publication Dordrecht, Netherlands
Publisher Springer
Collection year 2016
Language eng
Abstract In open channel, canals and rivers, a rapid increase in flow depth will induce a positive surge, also called bore or compression wave. The positive surge is a translating hydraulic jump. Herein new experiments were conducted in a large-size rectangular channel to characterise the unsteady turbulent properties, including the coupling between free-surface and velocity fluctuations. Experiments were repeated 25 times and the data analyses yielded the instantaneous median and instantaneous fluctuations of free-surface elevation, velocities and turbulent Reynolds stresses. The passage of the surge front was associated with large free-surface fluctuations, comparable to those observed in stationary hydraulic jumps, coupled with large instantaneous velocity fluctuations. The bore propagation was associated with large turbulent Reynolds stresses and instantaneous shear stress fluctuations, during the passage of the surge. A broad range of shear stress levels was observed underneath the bore front, with the probability density of the tangential stresses distributed normally and the normal stresses distributed in a skewed single-mode fashion. Maxima in normal and tangential stresses were observed shortly after the passage of a breaking bore roller toe. The maximum Reynolds stresses occurred after the occurrence of the maximum free-surface fluctuations, and this time lag implied some interaction between the free-surface fluctuations and shear stress fluctuations beneath the surge front, and possibly some causal effect.
Keyword Tidal bores
Positive surges
Compression waves
Turbulence
Turbulent Reynolds stresses
Physical modelling
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Civil Engineering Publications
Official 2016 Collection
 
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