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Solving Spillway Geometry for Three-dimensional Flow

Author: G.L. Coetzee, S.J. van Vuuren
Conference: 87th Annual Meeting of the International Commission on Large Dams
Date: June 9-14, 2019

ABSTRACT

The Ogee profile is one of the most studied hydraulic relationships used in the design of spillways. The high discharge efficiency and nappe-shaped profile ensure an effective hydraulic system, if applied under the correct conditions. However, in a recent study, the existing Ogee profile relationship, formulated for two-dimensional flow conditions, proved to be insufficient for three-dimensional flow conditions. Data obtained from a detailed physical model study and extensive computational fluid dynamic simulations allowed for a qualitative and quantitative comparison of the bottom nappe of the fluid profile across an aerated sharp-crested weir. The study concluded in the derivation of the VC-Ogee relationship that estimates the Ogee profile under three-dimensional flow conditions. Four parameters A, B, C and D, were incorporated to accommodate the effect of three-dimensional flow. A set of VC-Ogee design curves for these parameters, for an asymmetrical approach channel with side contraction of the spillway, is presented in this paper. Further design curves to accommodate symmetrical, contracted and uncontracted approach channels as well as combinations of these conditions, will be made available in future.

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