Abstract
With the re-evaluation and revision of a number of design floods, several embankment overtopping protection systems have been developed and a common technique is the construction of a stepped spillway on the downstream slope. For such moderate slope stepped channels, detailed air–water flow measurements were performed in a large facility with a focus on the rate of energy dissipation, flow resistance, air–water interfacial areas and re-aeration rates. Past and present experimental results showed a significant aeration of the flow. The median dimensionless residual head was about 3 × dc for the 21.8° sloping chute and smaller than that for flatter slopes (θ = 3.4° and 15.9°). The flow resistance results yielded an equivalent Darcy friction factor of about 0.25 implying a larger flow resistance for the 21.8° slope angle than for smaller slope angles. The re-aeration rate was deduced from the integration of the mass transfer equation using measured air–water interfacial areas and air–water flow velocities. The results suggested an increasing re-aeration rate with increasing rate of energy dissipation. The stepped invert contributed to intense turbulence production, free-surface aeration and large interfacial areas. The experimental data showed however some distinctive seesaw pattern in the longitudinal distribution of air–water flow properties with a wave length of about two step cavities. While these may be caused by the interactions between successive adjacent step cavities and their interference with the free-surface, the existence of such “instabilities” implies that the traditional concept of normal flow might not exist in skimming flows above moderate-slope stepped spillways.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
References
Amador A, Sanchez-Juny M, Dolz J (2006) Characterization of the non-aerated flow region in a stepped spillway by PIV. J Fluids Eng, ASME 128(6): 1266–1273. doi:10.1115/1.2354529
ASCE Task Committee (1994) Alternatives for overtopping protection of dams. ASCE, New York, 139 pp (Task Committee on Overtopping Protection)
Baker R (1994) Brushes clough wedge block spillway—progress report no 3. SCEL project report no SJ542-4. University of Salford, UK, 47 pp
Bakhmeteff BA (1932) Hydraulics of open channels. 1st edn. McGraw-Hill, New York, p 329
Boes RM (2000) Zweiphasenstroömung und Energieumsetzung an Grosskaskaden (Two-Phase Flow and Energy Dissipation on Cascades), PhD thesis, VAW-ETH, Zürich, Switzerland (in German)
Brattberg T, Chanson H, Toombes L (1998) Experimental investigations of free-surface aeration in the developing flow of two-dimensional water jets. J Fluids Eng Trans ASME 120(4): 738–744
Carosi G, Chanson H (2008) Turbulence characteristics in skimming flows on Stepped spillways. Can J Civ Eng 35(9): 865–880. doi:10.1139/L08-030
Chamani MR (2000) Air inception in skimming flow regime over stepped spillways. In: Minor HE, Hager WH (eds) International workshop on hydraulics of stepped spillways. Balkema Publ, Zürich, pp 61–67
Chanson H (1995) Hydraulic design of stepped cascades, channels, weirs and spillways. Pergamon, Oxford, p 292
Chanson H (2001) The hydraulics of stepped chutes and spillways. Balkema, Lisse, The Netherlands, p 418
Chanson H (2004) Environmental hydraulics of open channel flows. Elsevier Butterworth-Heinemann, Oxford, p 483
Chanson H (2006) Hydraulics of skimming flows on stepped chutes: the effects of inflow conditions?. J Hydraul Res, IAHR 44(1): 51–60
Chanson H, Toombes L (2001) Experimental investigations of air entrainment in transition and skimming flows down a stepped chute. Application to embankment overflow stepped spillways. Research report no CE158, Departmnt of Civil Engineering, The University of Queensland, Brisbane, Australia, 74 pp
Chanson H, Toombes L (2002a) Energy dissipation and air entrainment in a stepped storm waterway: an experimental study. J Irrigat Drain Eng, ASCE 128(5): 305–315
Chanson H, Toombes L (2002b) Experimental study of gas-liquid interfacial properties in a stepped cascade flow. Environ Fluid Mech 2(3): 241–263. doi:10.1023/A:1019884101405
Chanson H, Toombes L (2003) Strong interactions between free-surface aeration and turbulence in an open channel flow. Exp Therm Fluid Sci 27(5): 525–535. doi:10.1016/S0894-1777(02)00266-2
Chanson H, Yasuda Y, Ohtsu I (2002) Flow resistance in skimming flows and its modelling. Can J Civ Eng 29(6): 809–819. doi:10.1139/l02-083
Dodu J (1957) Etude de la Couche Limite d’Air autour d’un Jet d’Eau à Grande Vitesse (Study of the Boundary Layer around a High Velocity Water Jet). In: Proceedings of the 7th IAHR Congress, Lisbon, Portugal, paper D6 (in French)
Felder S, Chanson H (2008) Turbulence and turbulent length and time scales in skimming flows on a stepped spillway. Dynamic similarity, Physical modelling and scale effects, report no CH64/07. Division of Civil Engineering, The University of Queensland, Brisbane, Australia, 217 pp
Gonzalez CA (2005) An Experimental study of free-surface aeration on embankment stepped chutes. PhD thesis, Department of Civil Engineering, The University of Queensland, Brisbane, Australia, 240 pp
Gonzalez CA, Chanson H (2004) Interactions between cavity flow and main stream skimming flows: an experimental study. Can J Civ Eng 31(1): 33–44. doi:10.1139/l03-066
Gonzalez CA, Chanson H (2006) Flow characteristics of skimming flows in stepped channels. Discussion. J Hydraul Eng, ASCE 132(5): 537–539. doi:10.1061/(ASCE)0733-9429(2006)132:5(537)
Gonzalez CA, Chanson H (2007a) Experimental measurements of velocity and pressure distribution on a large broad-crested weir. Flow Meas Instrum 18(3–4): 107–113. doi:10.1016/j.flowmeasinst.2007.05.005
Gonzalez CA, Chanson H (2007) Hydraulic design of stepped spillways and downstream energy dissipators for embankment dams. Dam Eng 17(4): 223–244
Gosse P, Gregoire A (1997) Dispositif de Réoxygénation Artificielle du Sinnamary à l’Aval du Barrage de Petit-Saut (Guyane) (Artificial re-oxygenation of the sinnamary, downstream of Petit-Saut dam (French Guyana)). Hydroécol Appl 9(1–2): 23–56 (in French)
Grinchuk AS, Pravdivets YP, Shekhtman NV (1977) Test of earth slope revetments permitting flow of water at large specific discharges (Gidrotekhnicheskoe Stroitel’stvo (4):22–26 (in Russian)). (Translated in Hydrotechnical Construction, 1978, Plenum Publ, pp 367–373)
Henderson FM (1966) Open Channel Flow. MacMillan Company, New York
Jempson MA (2001) Flood and debris loads on bridges. PhD thesis, University of Queensland, Department of Civil Engineering, Australia, 429 pp
Kawase Y, Moo-Young M (1992) Correlations for liquid-phase mass transfer coefficients in bubble column reactors with Newtonian and non-Newtonian fluids. Can J Chem Eng 70(Feb): 48–54
Matos J (2000) Hydraulic design of stepped spillways over RCC dams. In: Minor HE, Hager WH (eds) Intl Workshop on Hydraulics of Stepped Spillways. Balkema Publ, Zürich, pp 187–194
Meireles I, Cabrita J, Matos J (2006) Non-aerated skimming flow properties on stepped chutes over small embankment dams. In: Matos J, Chanson H (eds) Proceedings of the international junior researcher and engineer workshop on hydraulic structures, IAHR, Montemor-o-Novo, Portugal, 2–4 Sept, hydraulic model report no CH61/06, Division of Civil Engineering, The University of Queensland, Brisbane, Australia, pp 91–99
Ohtsu I, Yasuda Y, Takahashi M (2004) Flow Characteristics of skimming flows in stepped channels. J Hydraul Eng, ASCE, 130(9):860–869. Discussion 132(5):527–542
Peyras L, Royet P, Degoutte G (1991) Ecoulement et Dissipation sur les Déversoirs en Gradins de Gabions (Flows and Dissipation of Energy on Gabion Weirs). J La Houille Blanche (1):37–47 (in French)
Rajaratnam N (1990) Skimming Flow in Stepped Spillways. J Hydraul Eng, ASCE 116(4):587–591. Discussion 118(1):111–114
Relvas AT, Pinheiro AN (2008) Inception point and air concentration in flows on stepped chutes lined with wedge-shaped concrete blocks. J Hydraul Eng, ASCE 134(8): 1042–1051
Robison R (1994) Chicago’s waterfalls. Civ Eng, ASCE 64(7): 36–39
Thorwarth J, Köngeter J (2006) Physical model tests on a stepped chute with pooled steps. Investigations of flow resistance and flow Instabilities. In: Marcano A, Martinez A (eds) Proceedings of the International symposium on hydraulic structures. IAHR, Ciudad Guayana, Venezuela, pp 477–486
Toombes L (2002) Experimental study of air–water flow properties on low-gradient stepped cascades. PhD thesis, Department of Civil Engineering, The University of Queensland, Brisbane, Australia
Toombes L, Chanson H (2005) Air–water mass transfer on a stepped waterway. J Environ Eng, ASCE 131(10): 1377–1386
Yasuda Y, Ohtsu IO (1999) Flow Resistance of skimming flow in stepped channels. In: Proceedings of the 28th IAHR Congress. Graz, Austria, Session B14, 6 pp
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Felder, S., Chanson, H. Energy dissipation, flow resistance and gas-liquid interfacial area in skimming flows on moderate-slope stepped spillways. Environ Fluid Mech 9, 427–441 (2009). https://doi.org/10.1007/s10652-009-9130-y
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10652-009-9130-y