Phase-detection measurements in free-surface turbulent shear flows

Chanson, Hubert (2016) Phase-detection measurements in free-surface turbulent shear flows. Journal of Geophysics and Engineering, 13 2: S74-S87. doi:10.1088/1742-2132/13/2/S74

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Author Chanson, Hubert
Title Phase-detection measurements in free-surface turbulent shear flows
Journal name Journal of Geophysics and Engineering   Check publisher's open access policy
ISSN 1742-2140
Publication date 2016-03-30
Sub-type Article (original research)
DOI 10.1088/1742-2132/13/2/S74
Open Access Status Not Open Access
Volume 13
Issue 2
Start page S74
End page S87
Total pages 14
Place of publication Bristol, United Kingdom
Publisher Institute of Physics Publishing
Collection year 2017
Language eng
Abstract High-velocity self-aerated flows are described as 'white waters' because of the entrained air bubbles. The air entrainment induces a drastic change in the multiphase flow structure of the water column and this leads to significant bubble-turbulence interactions, turbulence modulation and associated mixing processes impacting on the bulk flow properties. In these high-velocity free-surface turbulent flows, the phase-detection needle probe is a most reliable instrumentation. The signal processing of a phase-detection probe is re-visited herein. It is shown that the processing may be performed on the raw probe signal as well as the thresholded data. The latter yields the time-averaged void fraction, the bubble count rate, the particle chord time distributions and the particle clustering properties within the particulate flow regions. The raw probe signal analysis gives further the auto-correlation time scale and the power spectrum density function. Finally dimensional considerations are developed with a focus on the physical modelling of free-surface flows in hydraulic structures. It is argued that the notion of scale effects must be defined in terms of some specific set of air–water flow properties within well-defined testing conditions, while a number of free-surface flow characteristics are more prone to scale effects than others, even in large-size physical facilities.
Keyword Air bubble entrainment
Phase-detection probes
Void fraction
Bubble count rate
Interfacial velocity
Conductivity probes
Free-surface flows
High-velocity open channel flows
Hydraulic enginering
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
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Created: Fri, 01 Apr 2016, 05:55:24 EST by Hubert Chanson on behalf of School of Civil Engineering