Inception Point and Air Entrainment on Flows under Macroroughness Condition
Publication: Journal of Environmental Engineering
Volume 137, Issue 7
Abstract
Rock chutes or block ramps are fishway passages with low environmental impact. They also contribute to reaeration of rivers with low dissolved oxygen content, owing to the turbulence enhanced by their three-dimensional macroroughness conditions. This paper analyzes the air entrainment inception in flows over beds in macroroughness condition and the self-aerated flow features of the developing flow downstream of the inception point. Air concentration, inception point locations, and water depth elevations have been measured on two different scaled chutes for slopes ranging between 1V:5.88H and 1V:2.17H. Moreover, two different ogee crest lengths have been tested to assess the role of the inlet conditions on the location of the inception point. New equations have been developed to estimate the location of the point of inception and the respective water depth. Longitudinal variations of the mean air concentration downstream from the inception point have been studied and compared with data from the literature. An expression is presented to estimate the optimum length of the block ramp in natural rivers for maximizing air-water mixing.
Get full access to this article
View all available purchase options and get full access to this article.
References
André, S. (2004). “High velocity aerated flow on stepped chutes with macro-roughness elements.” Ph.D. thesis, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
Bathurst, J. C. (1985). “Flow resistance estimation in mountain rivers.” J. Hydraul. Eng., 111(4), 625–643.
Bindo, M., Gautier, J., and Çacroix, F. (1993). “The stepped spillway of M’Bali Dam.” Int. Water Power Dam Constr., 45(1), 35–36.
Boes, R. M. (2000). “Scale effects in modelling two-phase stepped spillway flow.” Proc., Hydraulics of Stepped Spillways, H.-E. Minor and W. H. Hager, eds., Balkema, Rotterdam, The Netherlands, 53–60.
Boes, R. M., and Hager, W. H. (2003a). “Hydraulic design of stepped spillways.” J. Hydraul. Eng., 129(9), 671–679.
Boes, R. M., and Hager, W. H. (2003b). “Two-phase flow characteristics of stepped spillways.” J. Hydraul. Eng., 129(9), 661–670.
Boes, R. M., and Minor, H.-E. (2000). “Guidelines for the hydraulic design of stepped spillways.” Proc., Hydraulics of Stepped Spillways, H.-E. Minor and W. H. Hager, eds., Balkema, Rotterdam, The Netherlands, 163–170.
Carosi, G., and Chanson, H. (2006). “Air-water time and length scales in skimming flows on a stepped spillway. Application to the spray characterisation.” Rep. No. CH59/06, Div. of Civil Engineering, The University of Queensland, Brisbane, Australia.
Castro-Orgaz, O., and Hager, W. H. (2010). “Drawdown curve and turbulent boundary layer development for chute flow.” J. Hydraul. Res., 48(5), 591–602.
Chamani, M. R. (2000). “Air inception in skimming flow regime over stepped spillways.” Proc., Int. Workshop on Hydraulics of Stepped Spillways, H.-E. Minor and W. H. Hager, eds., Balkema, Rotterdam, The Netherlands, 61–67.
Chanson, H. (1993). “Self-aerated flows on chutes and spillways.” J. Hydraul. Eng., 119(2), 220–243.
Chanson, H. (1994). “Hydraulics of skimming flows over stepped channels and spillways.” J. Hydraul. Res., 32(3), 445–460.
Chanson, H. (1995). “Air bubble entrainment in free-surface turbulent flows.” Rep. CH46/95, Dept. of Civil Engineering, Univ. of Queensland, Brisbane, Australia.
Chanson, H. (2001). “Hydraulic design of stepped spillways and downstream energy dissipators.” Dam Eng., 11(4), 205–242.
Chanson, H. (2006). “Hydraulics of skimming flows on stepped chutes: The effects of inflow conditions?” J. Hydraul. Res., 44(1), 51–60.
Chanson, H. (2009). “Embankment overflow protection system and earth dam spillways.” Dams: Impacts, stability and design, W. P. Hayes and M. C. Barnes, eds., Nova Science Publishers, Hauppauge, NY, 101–132.
Chanson, H., and Carosi, G. (2007). “Turbulent time and length scale measurements in high-velocity open channel flows.” Exp. Fluids, 42(3), 385–401.
Chanson, H., and Toombes, L. (2001). Experimental investigations of air entrainment in transition and skimming flows down a stepped chute: Application to embankment overflow stepped spillways. Rep. CE 158, Dept. of Civil Engineering, University of Queensland, Brisbane, Australia.
Chow, V. T. (1959). Open channel hydraulics, McGraw-Hill, New York.
Dey, S., and Raikar, R. V. (2007). “Characteristic of loose rough boundary streams at near threshold.” J. Hydraul. Eng., 133(3), 288–204.
Essery, I. T. S., Tebbutt, T. H. Y., and Rasaratnam, S. K. (1978). “Design of spillways for re-aeration of polluted waters.” CIRIA Rep. 72, London.
Ferrando, A. M., and Rico, J. R. (2002). “On the incipient aerated flow in chutes and spillways.” J. Hydraul. Res., 40(1), 95–97.
Ferro, V., Della Fontana, G., Pagliara, S., Puglisi, S., and Scotton, P. (2004). Opere di sistemazione idraulico-forestale a basso impatto ambientale (Hydraulic-forestal low environmental impact control structures), McGraw-Hill, Milan, Italy (in Italian).
Frizell, K. H., Mefford, B. W., Dodge, R. A., and Vermeyen, T. B. (1991). “Embankments dams: Methods of protection during overtopping.” Hydro Review, 10(2), 19–30.
Gangadharaiah, T., Rao, N. S. L., and Seetharamaiah, K. (1970). “Inception and entrainment in self-aerated flows.” J. Hydraul. Div., 96(HY7), 1549–1565.
Gaston, M. L. (1995). “Air entrainment and energy dissipation on a stepped block spillway.” M.Sc. thesis, Colorado State Univ., Fort Collins, CO.
Gonzalez, C. A. (2005). “An experimental study of free-surface aeration on embankment stepped chutes.” Ph.D. thesis, Univ. of Queensland, Brisbane, Australia.
Hughes, W. C., and Flack, E. J. (1984). “Hydraulic jump properties over a rough bed.” J. Hydraul. Eng., 110(12), 1755–1771.
Hunt, S. L., and Kadavy, K. C. (2009). “Inception point relationship for flat-sloped stepped spillways.” 2009 Annual International Meeting, American Society of Agricultural and Biological Engineers, Reno, NV.
James, C. S., et al. (2001). “Onset of skimming flow on stepped spillways.” J. Hydraul. Eng., 127(6), 519–525.
Kucukali, S., and Cokgor, S. (2009). “Energy concept for predicting hydraulic jump aeration efficiency.” J. Environ. Eng., 135(2), 105–107.
Mateos, I., and Elviro, G. (1997). “Initiation of aeration in stepped-spillways.” Proc. 27th International Association for Hydro-Environment Engineering Congress, Theme D, ASCE, Reston, VA, 589–594.
Matos, J. (1999). “Emulsionamento de ar e dissipação de energia do escoamento em descarregadores em degraus.” Ph.D. thesis, Technical Univ. of Lisbon, Lisbon, Portugal.
Matos, J. (2000a). “Discussion of hydraulics of skimming flow on modeled stepped spillways.” J. Hydraul. Eng., 126(12), 948–950.
Matos, J. (2000b). “Hydraulic design of stepped spillways over RCC dams.” Proc. Hydraulics of Stepped Spillways, H.-E. Minor and W. H. Hager, eds., Balkema, Rotterdam, The Netherlands, 187–194.
Matos, J., and Frizell, K. H. (1997). “Air concentration measurements in highly turbulent aerated flow.” 27th International Association for Hydro-Environment Engineering Congress, Theme B, ASCE, Reston, VA, 149–154.
Matos, J., and Frizell, K. H. (2000). “Air concentration and velocity measurements on self-aerated flow down stepped chutes.” Proc., ASCE 2000 Conf. (CD-ROM), ASCE, Reston, VA, 1–12.
Meireles, I., Matos, J., and Frizell, K. (2007). “Measuring air entrainment and flow bulking in skimming flow over steeply sloping stepped chutes.” Proc., Hydraulic Measurements and Experimental Methods Conf. (CD-ROM), ASCE Environmental and Water Resources Institute, Reston, VA.
Moog, D. B., and Jirka, G. H. (1999). “Stream reaeration in nonuniform flow: Macroroughness enhancement.” J. Hydraul. Eng., 125(1), 11–16.
Ohtsu, I., Yasuda, Y., and Takahashi, M. (2000). “Discussion of characteristics of skimming flow over stepped spillways by M. R. Chamani and N. Rajaratnam.” J. Hydraul. Eng., 126(11), 869–870.
Ohtsu, I., Yasuda, Y., and Takahashi, M. (2001). “Discussion of ‘Onset of skimming flow on stepped spillways’ by M. R. Chamani and N. Rajaratnam.” J. Hydraul. Eng., 127(6), 522.
Pagliara, S., Carnacina, I., and Roshni, T. (2010a). “Air-water flows in presence of staggered and row boulders under macro-roughness conditions.” Water Resour. Res., 46, W08535.
Pagliara, S., Carnacina, I., and Roshni, T. (2010b). “Self-aeration and friction over rock chutes in uniform flow conditions.” J. Hydraul. Eng., 136(11), 959–964.
Pagliara, S., Das, R., and Carnacina, I. (2008). “Flow resistance in large-scale roughness condition.” Can. J. Civ. Eng., 35(11), 1285–1293.
Pagliara, S., Roshni, T., and Carnacina, I. (2009). “Aeration and velocity profile over block ramp elements.” 33rd IAHR Congress—Water Engineering for a Sustainable Environment, International Association for Hydro-Environment Engineering, Vancouver, Canada, 4925–4932.
Pierson, W. L., and Cameron, S. (2006). “Design of rock protection to prevent erosion by water flows down steep slopes.” J. Hydraul. Eng., 132(10), 1110–1114.
Relvas, A. T., and Pinheiro, A. N. (2008). “Inception point and air concentration in flows on stepped chutes lined with wedge-shaped concrete blocks.” J. Hydraul. Eng., 134(8), 1042–1051.
Rice, C. E., Kadavy, K. C., and Robinson, K. M. (1998). “Roughness of loose rock riprap on steep slopes.” J. Hydraul. Eng., 124(2), 179–185.
Sorensen, R. M. (1985). “Stepped spillway hydraulic model investigation.” J. Hydraul. Eng., 111(12), 1461–1472.
Strom, K. B., and Papanicolaou, A. N. (2007). “ADV measurements around a cluster microform in a shallow mountain stream.” J. Hydraul. Eng., 133(12), 1379–1389.
Toombes, L., and Chanson, H. (2005). “Air-water mass transfer on a stepped waterway.” J. Environ. Eng., 131(10), 1377–1386.
Tozzi, M. J. (1992). Caracterização/Comportamento de escoamentos em vertedouros com paramento em degraus, Politechnic School of Univ. of Sao Paulo, Sao Paulo, Brazil.
Wood, I. R. (1983). “Uniform region of self aerated flow.” J. Hydraul. Eng., 109(3), 447–461.
Wood, I. R. (1985). “Air water flows.” Proc., 21st IAHR Congress, Melbourne, Australia, 18–29.
Wood, I. R., Ackers, P., and Loveless, J. (1983). “General method for critical-point on spillways.” J. Hydraul. Eng., 109(2), 308–312.
Information & Authors
Information
Published In
Journal of Environmental Engineering
Volume 137 • Issue 7 • July 2011
Pages: 629 - 638
Copyright
© 2011 American Society of Civil Engineers.
History
Received: Jul 29, 2010
Accepted: Jan 31, 2011
Published online: Feb 1, 2011
Published in print: Jul 1, 2011
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.