Energy Dissipation and Air Entrainment in a Stepped Storm Waterway: an Experimental Study

Chanson, H. and Toombes, L. (2002) Energy Dissipation and Air Entrainment in a Stepped Storm Waterway: an Experimental Study. Journal of Irrigation and Drainage Engineering, 128 5: 305-315.

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Author Chanson, H.
Toombes, L.
Title Energy Dissipation and Air Entrainment in a Stepped Storm Waterway: an Experimental Study
Journal name Journal of Irrigation and Drainage Engineering   Check publisher's open access policy
ISSN 0733-9437
Publication date 2002-01-01
Sub-type Article (original research)
DOI 10.1061/(ASCE)0733-9437(2002)128:5(305)
Volume 128
Issue 5
Start page 305
End page 315
Total pages 11
Editor John C. Guitjens
Place of publication New York
Publisher Americaln Society of Civil Engineers, Irrigation and Drainage Division
Collection year 2002
Language eng
Subject 291100 Environmental Engineering
290802 Water and Sanitary Engineering
300105 Applied Hydrology (Drainage, Flooding, Irrigation, Quality, etc.)
290800 Civil Engineering
770400 Coastal and Estuarine Environment
Abstract For the last three decades, research focused on steep stepped chutes. Few studies considered flat-slope stepped geometries such as stepped storm waterways or culverts. In this study, experiments were conducted in a large, flat stepped chute (~3.4 degrees) based upon a Froude similitude. Three basic flow regimes were observed: nappe flow without hydraulic jump, transition flow, and skimming flow. Detailed air-water flow measurements were conducted. The results allow a complete characterization of the air concentration and bubble count rate distributions, as well as an accurate estimate of the rate of energy dissipation. The flow resistance, expressed in terms of a modified friction slope, was found to be about 2.5 times greater than in smooth-chute flow. A comparison between smooth- and stepped-invert flows shows that greater aeration and larger residence times take place in the latter geometry. The result confirms the air-water mass transfer potential of stepped cascades, even for flat slopes (<5 degrees).
Keyword stepped waterway
energy dissipation
flow aeration
air entrainment
spillway aeration device
physical modelling
References Brattberg, T., Chanson, H., and Toombes, L. (1998). Experimental investigations of free-surface aeration in the developing flow of twodimensional water jets. J. Fluids Eng., 120(4), 738-744. Chanson, H. (1989a). Study of air entrainment and aeration devices. J. Hydraul. Res., 27(3), 301-319. Chanson, H. (1989b). Flow downstream of an Aerator. Aerator spacing. J. Hydraul. Res., 27(4), 519-536. Chanson, H. (1995a). Hydraulic design of stepped cascades, channels, weirs, and spillways, Pergamon, Oxford. Chanson, H. (1995b). Air bubble entrainment in free-surface turbulent flows. Experimental investigations. Rep. No. CH46/95, Dept. of Civil Engineering, Univ. of Queensland, Australia. Chanson, H. (1996). Prediction of the transition nappe/skimming flow on a stepped channel. J. Hydraul. Res., 34(3), 421-429. Chanson, H. (1997a). Air bubble entrainment in free-surface turbulent shear flows, Academic, London. Chanson, H. (1997b). Air bubble entrainment in open channels. Flow structure and bubble size distributions. Int. J. Multiphase Flow, 23(1), 193-203. Chanson, H., and Brattberg, T. (2000). Experimental study of the air-water shear flow in a hydraulic jump. Int. J. Multiphase Flow, 26(4), 583-607. Chanson, H., and Toombes, L. (1997). Energy dissipation in stepped waterway. Proc., 27th IAHR Congress, San Francisco, Vol. D, F. M. Holly Jr. and A. Alsaffar, eds., 595-600. Cui, L. (1985). Air concentration distribution downstream of aeration ramp. Shuili Xuebao (J. Hydraul. Eng.), Beijing, China, 1, 45-50 (in Chinese). Evans, A. H. (1928). The Palace of Minos: A comparative account of the successive stages of the early Cretan civilization as illustrated by the discoveries at Knossos, Vol. II, Part 1, Macmillan, London. Kazemipour, A. K., and Apelt, C. J. (1983). Effects of irregularity of form on energy losses in open channel flow. Aust. Civil Eng. Trans., Vol. CE25, Institution of Engineers, Australia, 294-299. Low, H. S. (1986). Model studies of clyde dam spillway aerators. Research Rep. No. 86-6, Dept. of Civil Engineering, Univ. of Canterbury, Christchurch, New Zealand. Noori, B. M. A. (1984). Form drag resistance of two dimensional stepped steep open channels. Proc., 1st Int. Conf. on Hydraulic Design in Water Resources Engineering, Channels and Channel Control Structures, Southampton, U.K., K. V. H. Smith, ed., Springer, Berlin, 1.133-1.147. Ohtsu, I., and Yasuda, Y. (1997). Characteristics of flow conditions on stepped channels. Proc., 27th IAHR Biennal Congress, San Francisco, Theme D, 583-588. Rajaratnam, N. (1990). Skimming flow in stepped spillways. J. Hydraul. Eng., 116(4), 587-591. Robison, R. (1994). Chicago's waterfalls. Civ. Eng., 64(7), 36-39. Shi, Q., Pan, S., Shao, Y., and Yuan, X. (1983). Experimental investigation of flow aeration to prevent cavitation erosion by a deflector. Shuili Xuebao (J. Hydraul. Eng.), Beijing, China, 3, 1-13 (in Chinese).
Q-Index Code C1
Additional Notes 2004 American Society of Civil Engineers, Environmental and Water Resources Institute (ASCE-EWRI) award for the best practice paper in the Journal of Irrigation and Drainage Engineering

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Created: Mon, 22 Aug 2005, 10:00:00 EST by Hubert Chanson on behalf of School of Engineering