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

H. Chanson, L. Toombes
2002 Journal of irrigation and drainage engineering  
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 ͑ϭ3.4°͒ 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
more » ... terization 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 ͑Ͻ5°͒.
doi:10.1061/(asce)0733-9437(2002)128:5(305) fatcat:eshm4a6apjgw5cz4t2rtufkogu