An experimental study of effects of step roughness in skimming flows on stepped chutes / Gonzalez, Carlos A. in Journal of hydraulic research, Vol. 46 extra issue (2008)  

An experimental study of effects of step roughness in skimming flows on stepped chutes = Etude expérimentale des effets de la rugosité des marches sur les écoulements d'écumage dans les évacuateurs en gradins [texte imprimé] / Gonzalez, Carlos A., Auteur ; Masayuki Takahashi, Auteur ; Chanson, Hubert, Auteur . - 2008 . - p. 24-35.
Hydraulique
Résumé en Français
Langues : Anglais (eng)
in Journal of hydraulic research > Vol. 46 extra issue (2008) . - p. 24-35

Mots-clés :	Stepped chute Skimming flow Step roughness Air-water Physical modelling Flow resistance Form drag Energy dissipation Gabion stepped spillway
Index. décimale :	627 Ingénierie des cours d'eau naturels, des ports, des rades et des cotes. Installations de navigation, de dragage, de récupération et de sauvetage. Barrages et centrales électriques hydrauliques
Résumé :	On a spillway chute, a stepped design increases the rate of energy dissipation on the chute itself and reduces the size of a downstream energy dissipater. Up to date, the effects of step roughness on the flow properties remain unknown despite the practical relevance to damaged concrete steps, rock chutes and gabions weirs. New measurements were conducted in a large-size laboratory facility with two step conditions (smooth and rough) and three types of step roughness. Detailed air-water flow properties were measured systematically for several flow rates. The results showed faster flow motion on rough step chutes. Although the finding is counter-intuitive, it is linked with the location of the inception point of free-surface aeration being located further downstream than for a smooth stepped chute for an identical flow rate. In the aerated flow region, the velocities on rough-step chutes were larger than those of smooth chute flows for a given flow rate and dimensionless location from the inception point of free-surface aeration both at step edges and between step edges. The results suggest that design guidelines for smooth (concrete) stepped spillway may not be suitable to rough stepped chutes including gabion stepped weirs, and older stepped chutes with damaged steps.
DEWEY :	627
ISSN :	0022-1686
En ligne :	http://www.journalhydraulicresearch.com/