Author(s): S. Erpicum; B. Blancher; Y. Peltier; J. Vermeulen; P. Archambeau; B. Dewals; M. Pirotton
Linked Author(s): Sébastien Erpicum, Yann PELTIER, Benjamin J. Dewals
Keywords: Spillway; Free surface weir; Experimental modelling; Discharge coefficient; Quadrant geometry; Cavitation risk
Abstract: The effect on the flow characteristics of the upstream quadrant shape of four ogee spillways is investigated at high head operation by means of experimental modelling. Each spillway is designed following the latest recommendations of the U. S. Army Corps of Engineers. The upstream and downstream quadrants of the reference spillway have the same design head. The absence of scale-effects is verified with a second reference spillway designed with a smaller head. The last spillway has an upstream quadrant with a design head respectively larger and smaller than the one of the downstream quadrant. The discharge coefficient is evaluated until head ratios of five for each case and until seven for the smaller model. The discharge coefficient continuously increases until a head ratio of 5.5 and then drops due to a flow separation at the spillway crest. The spillway efficiency (discharge coefficient) reduces with an oversized upstream quadrant while an undersized quadrant has no effect, but it does affect the measured relative pressure and thus the risk of cavitation.