Experimental investigation of flow pattern and energy dissipation rate in stepped spillways

Mero, Shimal Khalid (2013) Experimental investigation of flow pattern and energy dissipation rate in stepped spillways. MSc dissertation, University of Portsmouth.

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    Abstract

    Stepped spillways are a hydraulic and cost effective measure to dissipate energy of large water flows over the spillway of a dam. Like other spillway types, it has some limitations and a measure to improve the energy dissipation is proposed. The hydraulics of stepped spillways with flat steps are well documented and some design guidelines exist for the slopes of the spillways as they apply to typical embankment dams. However, the hydraulic characteristics of alternative stepped designs are poorly understood. In the present study, a series of experiments was conducted on a large stepped spillway model with a moderate slope (26.6º) for a range of discharges between 0.0121 and 0.0213 m3/s. In some experiments, the stepped chute was fitted with uniform steps of 5 cm height, then in addition several new step configurations, such as horizontally inclined and curved steps with and without reflector blocks, were investigated. For each configuration, the flow pattern, energy dissipation and residual energy were measured for a range of discharges. The results over a flat stepped spillway were compared with the results over flat steps in a number of similar, previous studies, and with the results obtained from the new step configurations. Skimming, transitional and nappe flow regimes were all identified. The comparative study highlighted the similarity between the results over flat steps in this study and previous studies. The findings show that horizontally inclined and curved step configurations dissipated about twice as much energy as flat steps, but the flow pattern of the new step configurations showed some instabilities. Overall, the new step configurations exhibited rather less stable flow patterns than the flat stepped design, and were characterised by a higher rate of energy dissipation and lower residual energy than the flat step design, for the particular slope investigated (θ = 26.6°).

    Item Type: Dissertation
    Departments/Research Groups: Faculty of Technology > School of Civil Engineering and Surveying
    Depositing User: Beth Atkins
    Date Deposited: 01 Aug 2014 09:19
    Last Modified: 28 Jan 2015 12:39
    URI: http://eprints.port.ac.uk/id/eprint/15159

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