Characterisation of interfacial aeration in high-velocity free-surface air-water flows: what does 50% void fraction mean?

Felder, S. and Chanson, H. (2014). Characterisation of interfacial aeration in high-velocity free-surface air-water flows: what does 50% void fraction mean?. In: Harun Chowdhury and Firoz Alam, The Proceedings of the 19th Australasian Fluid Mechanics Conference. 19AFMC: 19th Australasian Fluid Mechanics Conference, Melbourne, VIC, Australia, (1-4). 8-11 December, 2014.

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Author Felder, S.
Chanson, H.
Title of paper Characterisation of interfacial aeration in high-velocity free-surface air-water flows: what does 50% void fraction mean?
Conference name 19AFMC: 19th Australasian Fluid Mechanics Conference
Conference location Melbourne, VIC, Australia
Conference dates 8-11 December, 2014
Proceedings title The Proceedings of the 19th Australasian Fluid Mechanics Conference
Place of Publication Clayton, VIC, Australia
Publisher Australasian Fluid Mechanics Society
Publication Year 2014
Sub-type Fully published paper
Open Access Status
ISBN 9780646596952
Editor Harun Chowdhury
Firoz Alam
Issue Paper 235
Start page 1
End page 4
Total pages 4
Collection year 2015
Language eng
Formatted Abstract/Summary
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 50%. Herein a detailed experimental study was conducted in the intermediate flow region 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 chord modes with increasing bubble count rates was observed. Several characteristic time scales were identified based upon interparticle 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 turbulent time scales within this region of the flow. A further characteristic time scale of 100 ms was identified in a frequency analysis of the 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 free-surface instabilities.
Q-Index Code E1
Q-Index Status Confirmed Code
Institutional Status UQ

 
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Created: Wed, 03 Dec 2014, 06:39:35 EST by Hubert Chanson on behalf of School of Civil Engineering