Start Date

2018 11:50 AM

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

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 US 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 spillways have 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 5 for each case and until 7 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 on the measured relative pressure and thus the risk of cavitation.

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May 16th, 11:50 AM

Experimental Study of Ogee Crested Weir Operation Above the Design Head and Influence of the Upstream Quadrant Geometry

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 US 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 spillways have 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 5 for each case and until 7 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 on the measured relative pressure and thus the risk of cavitation.