Dynamic Similarity and Scale effects in Turbulent Free-Surface Flows above Triangular Cavities

Chanson, Hubert and Felder, Stefan (2007). Dynamic Similarity and Scale effects in Turbulent Free-Surface Flows above Triangular Cavities. In: Peter Jacobs, Tim McIntyre, Matthew Cleary, David Buttsworth, David Mee, Rose Clements, Richard Morgan and Charles Lemckert, 16th Australasian Fluid Mechanics Conference (AFMC). 16th Australasian Fluid Mechanics Conference (AFMC), Gold Coast, Queensland, Australia, (691-698). 3-7 December, 2007.

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Author Chanson, Hubert
Felder, Stefan
Title of paper Dynamic Similarity and Scale effects in Turbulent Free-Surface Flows above Triangular Cavities
Conference name 16th Australasian Fluid Mechanics Conference (AFMC)
Conference location Gold Coast, Queensland, Australia
Conference dates 3-7 December, 2007
Proceedings title 16th Australasian Fluid Mechanics Conference (AFMC)
Journal name Proceedings of the 16th Australasian Fluid Mechanics Conference, 16AFMC
Place of Publication Brisbane, Australia
Publisher School of Engineering, The University of Queensland
Publication Year 2007
Year available 2007
Sub-type Fully published paper
Open Access Status File (Author Post-print)
ISBN 978-1-864998-94-8
Editor Peter Jacobs
Tim McIntyre
Matthew Cleary
David Buttsworth
David Mee
Rose Clements
Richard Morgan
Charles Lemckert
Start page 691
End page 698
Total pages 8
Collection year 2007
Language eng
Abstract/Summary In high-velocity free-surface flows, air is continuously trapped and released through the interface, and the resulting air-water mixture are subjected to intense interactions between entrained air and turbulence. Two-phase flow properties were measured herein in high-velocity open channel flows above triangular cavities. Detailed turbulence measurements were conducted in a large-size facility to test the validity of the Froude and Reynolds similarities. The results showed consistently that the Froude similitude was not satisfied using a 2:1 geometric scaling ratio. Lesser number of entrained bubbles and comparatively greater bubble sizes were observed at the smaller Reynolds numbers, as well as lower turbulence levels and larger turbulent length and time scales. In practical terms, small-size models did underestimate the rate of energy dissipation and the aeration efficiency of prototype stepped spillways for similar flow conditions. Similarly a Reynolds similitude was tested. The results showed also some significant scale effects. However a number of self-similar relationships remained invariant under changes of scale and confirmed the analysis of Chanson and Carosi (2007). The finding is significant and suggests that self-similarity may provide a picture general enough to be used to characterise the air-water flow field in large prototype channels.
Subjects 290000 Engineering and Technology
290800 Civil Engineering
290802 Water and Sanitary Engineering
291800 Interdisciplinary Engineering
291803 Turbulent Flows
Keyword Turbulent skimming flows
Triangular cavity
Free-surface aeration
Dynamic similarity
Scale effects
Physical modelling
Froude similitude
Reynolds similitude
Stepped spillways
Air bubble entrainment
Integral turbulent length and time scales
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Q-Index Code E1
Additional Notes The full bibliographic details are: CHANSON, H., and FELDER, S. (2007). "Dynamic Similarity and Scale effects in Turbulent Free-Surface Flows above Triangular Cavities." Proc. 16th Australasian Fluid Mechanics Conference AFMC, Gold Coast, Australia, 2-7 December, P. JACOBS, T. McINTYRE, M. CLEARY, D. BUTTSWORTH, D. MEE, R. CLEMENTS, R. MORGAN, C. LEMCKERT Eds., pp. 691-698 (CD-ROM) (ISBN 978-1-864998-94-8).

 
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Created: Wed, 05 Dec 2007, 15:57:08 EST by Hubert Chanson on behalf of School of Engineering