The hydraulics of flow on stepped ogee-profile spillways.

Title: The hydraulics of flow on stepped ogee-profile spillways.
Authors: Azhdary Moghaddam, Mehdi.
Date: 1997
Abstract: Because of its simple form, its effectiveness as an energy dissipator, and its contribution to dam stability, the stepped spillway is one of the oldest drop structure used in the construction of small dams. With the relatively recent introduction of Roller Compacted Concrete (RCC) and particularly (rockfill) gabions as dam construction materials, the stepped spillways continues to be an attractive option among the various traditional forms of drop structure for small dams. The steps on the spillway's downstream face significantly increase the energy dissipation thereon over that would occur on the equivalent smooth (ogee-profile) version. As a consequence stilling basin structures, usually introduced at the toe of spillways (to reduce excess energy in the spillway floor) can be either reduced in size or eliminated entirely. Although stepped spillways were first introduced around 694 B.C., in most previous studies dealing with the hydraulic performance of stepped spillways are site-specific. This research, which includes both mathematical and physical elements, investigates the effect of different step configurations, in contribution with different spillway slopes, on the hydraulic performance of (ogee-profile) stepped spillways. The main goal of the research was to develop improved criteria for the design of stepped spillways. The numerical study, a 2-D finite element model was developed to estimate, based on a trial-error procedure, the stepped spillway water surface for a given design head. In the supporting experimental programme three different spillway slopes (45$\sp\circ$, 50$\sp\circ$, and 60$\sp\circ$) were investigated and in each case the experiments were repeated for four different step configurations. This provides data set of 12 combinations of spillway slope and step arrangement. Improved criteria were developed to (i) distinguish between the possible flow regimes on stepped spillways, (ii) estimate both stepped spillway friction factors and energy dissipation rates, and (iii) determine optimum step configurations for a given set of boundary conditions.
CollectionTh├Ęses, 1910 - 2010 // Theses, 1910 - 2010
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