Air–water flow characteristics in high-velocity free-surface flows with 50% void fraction

Felder, Stefan and Chanson, Hubert (2016) Air–water flow characteristics in high-velocity free-surface flows with 50% void fraction. International Journal of Multiphase Flow, 85 186-195. doi:10.1016/j.ijmultiphaseflow.2016.06.004

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Author Felder, Stefan
Chanson, Hubert
Title Air–water flow characteristics in high-velocity free-surface flows with 50% void fraction
Journal name International Journal of Multiphase Flow   Check publisher's open access policy
ISSN 0301-9322
Publication date 2016-10
Year available 2016
Sub-type Article (original research)
DOI 10.1016/j.ijmultiphaseflow.2016.06.004
Open Access Status Not Open Access
Volume 85
Start page 186
End page 195
Total pages 10
Place of publication Kidlington, Oxford, United Kingdom
Publisher Pergamon Press
Collection year 2017
Language eng
Formatted abstract
High-velocity free-surface flows are complex two-phase flows and limited information is available about the interactions between air and water for void fractions of about 50%. Herein a detailed experimental study was conducted in the intermediate flow region (C ∼ 50%) on a stepped spillway and the microscopic air–water flow characteristics were investigated. The results showed differences in water and droplet chord times with comparatively larger number of air chord times (0–2 ms), and larger number of water chord times (2–6 ms). A monotonic decrease of particle chord modes was observed with increasing bubble count rates. Several characteristic time scales were identified based upon inter-particle arrival time analyses of characteristic chord time classes as well as spectral analyses of the instantaneous void fraction signal. Chord times of 3–5 ms appeared to be characteristic time scales of the intermediate flow region having similar time scales compared to the local correlation and integral turbulent time scales and to time scales associated with bubble break-up and turbulent velocity fluctuations. A further characteristic time scale of 100 ms was identified in a frequency analysis of instantaneous void fraction. This time scale was of the same order of magnitude as free-surface auto-correlation time scales suggesting that the air–water flow structure was affected by the free-surface fluctuations.
Keyword High-velocity free-surface flows
Air–water time scales
Interfacial aeration
Bubble droplet interactions
Microscopic flow properties
Characteristic frequencies
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ
Additional Notes The deposit is a preprint. The full bibliographic details are: FELDER, S., and CHANSON, H. (2016). "Air–water flow characteristics in high-velocity free-surface flows with 50% void fraction." International Journal of Multiphase Flow, Vol. 85, pp. 186-195(DOI: 10.1016/j.ijmultiphaseflow.2016.06.004) (ISSN 0301-9322).

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Civil Engineering Publications
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Created: Mon, 01 Aug 2016, 06:13:30 EST by Hubert Chanson on behalf of School of Civil Engineering