Assessment of the Curvature and Slope for the VC-Ogee Relationship Allowing for 3D Flow

Author: G. L. Coetzee, S. J., van Vuuren
Conference: AFRICA 2017
Date: March 14-16, 2017

The van Vuuren and Coetzee (VC) Ogee relationship was introduced at ICOLD 2016 (van Vuuren & Coetzee, 2016) and is the only Ogee profile relationship that compensates for the effects of 3-dimensional flow that results from the upstream approach channel. This VC-Ogee relationship is distinguishable due to its derivation from both physical and numerical modelling of prominent 3-dimensional flow in the approach channel. The derived relationship uses four parameters to adjust the curvature and slope of the Ogee profile, depending on the upstream approach channel layout conditions. When compares to existing relationships (accounting only for 2-dimensional flow), the VC-Ogee relationship improves the crest pressure distribution resulting in reduced negative pressures for flows exceeding the design head. Furthermore, the VC-Ogee relationship has a gradual slope, with no abrupt change in the curvature, thereby reducing the possibility of flow breakaway that may contribute to cavitation damage of the structure. 


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