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Title: Computational investigation of flow over gabion spillways
Author: Zuhaira, Ali A. A.
ISNI:       0000 0004 7425 5209
Awarding Body: Swansea University
Current Institution: Swansea University
Date of Award: 2018
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A spillway is a hydraulic structure that is used to pass high discharges in flood seasons in a controlled way and also to release surplus water that cannot be safely stored in the reservoir to downstream. Stepped spillways and gabion stepped spillways have been used for centuries as an effective and efficient way of dissipating the energy of overflowing water. The steps of the spillway’s surface increase its roughness and therefore can generate high turbulence levels. Three main flow regimes can be identified over stepped spillways; namely nappe, transition and skimming flow depending on step size and water discharge. Under skimming flow conditions, the aerated and non-aerated flow regions can be clearly recognised over the chute slope depending on the air content. Investigation of the hydraulics of skimming flow conditions over gabion stepped spillways have been exclusively experimental to date, and have concentrated on the aerated zone under skimming flow conditions. Our knowledge of the flow properties in the non-aerated flow region over gabion steps is lacking and further research is required to improve the hydraulic structure design. This thesis describes the research undertaken to address this need. It is primarily a computational study but includes some experimental work for model validation. The numerical code is initially validated against different laboratory experimental data. The results indicated that the numerical code is robust in predicting flow field variables over gabion stepped spillways. The validated code is then applied to different cases of gabion stepped spillways, to explore the behaviour of the skimming flow with various step heights, chute slopes and step shapes. This work provides new insights into the hydraulics of skimming flow conditions in the non-aerated flow region over gabion stepped spillways. The computational results of this study have important implications for designing gabion stepped chutes, such as determining the position of free surface aeration and optimum step configuration.
Supervisor: Reeve, Dominic ; Karunarathna, Harshinie Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral