Abstract: One of the oldes problems of critical flow in open-channel hydraulics is rise in the channel bottom, which causes a critical flow at the weir crest. Although the classic hydraulic theory for parallel flow shows the usefulness of critical flow leading to unique head-discharge relations over the weir, in practice the parallel flow condition is unreal; theoretical analysis of round-crested weirs is thus restricted to teaching purposes or is used as a rough indication of flow characteristics before using more complete methods. The spillway problem has been treated previously with more laborious methods, either using two-dimensional (2D) hydrodynamic flow nets or accurate physical model experiments. A new extended Bernoulli energy equation, which is valid for moderately curved channel flows, is presented. From this equation, a higher-order critical flow condition suitable for a curved streamline flow has been developed. As a practical application, the flow over spillway profiles used in dam engineering has been studied. The proposed new critical flow theory makes it possible to simulate flow features with a reasonable agreement up to design conditions of the spillway, thus obtaining accurate results in situations in which the velocity is non-uniform, the pressure is non-hydrostatic and conventional critical flow theory is not valid.
Publication Year: 2008
Publication Date: 2008-01-01
Language: en
Type: article
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