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Experimental and numerical investigation of scour downstream contracted spillways

Tarek H. Nasralla

Journal of Water and Land Development | 2022 | No 52 | 53-59 | DOI: 10.24425/jwld.2021.139943

Keywords buffers contraction downstream Flow 3D scour spillway

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Abstract

A study of scour downstream of free hydraulic jump in stilling basin of stepped spillways was carried out. This paper employed an experimental study to investigate the stepped spillway with the movable bed material of D50 = 3.1 mm. The effect of the contraction ratio of the stepped spillway was highlighted. Different downstream divergent angle was studied to minimise the scour depth, the results showed that the relative scour depth was reduced by 23% for divergent angle is equal to 170°, different shapes of buffer in stilling basin were also studied to reduce the scour depth where the considered buffer decrease the relative scour depth up to 84%. This study was simulated by Flow 3D program to analyse the scour hole formed using velocity vectors at the bed. The simulated results well agreed with the measured data.

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Authors and Affiliations

Tarek H. Nasralla

Benha University, Benha Faculty of Engineering, Civil Engineering Department, 13512, Benha, Qalubiya, Egypt

Numerical investigations of stilling basin efficiency downstream radial gates – A case study of New Assuit Barrage, Egypt

Mohamed Elberry Abdelazim Ali Fahmy Abdelhaleem Amir Ibrahim

Journal of Water and Land Development | 2023 | No 59 | 126-134 | DOI: 10.24425/jwld.2023.147237

Keywords Flow-3D New Assuit Barrage riprap stability stilling basin verification

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Abstract

Radial gates are more common than vertical sluice gates for a number of reasons. They are simpler to use, cause less flow disturbance, require less lifting force, and deliver better discharge. Radial gates are commonly used in new barrages, such as the New Assuit Barrage. Prior researchers used physical investigations to study the efficiency of stilling basin downstream radial gates, but physical studies cost a lot of money and time, so numerical solutions should be investigated. The current study aimed to explore numerically the influence of stilling basin shape and baffle block arrangement on the stability of bed protection, near-bed velocity, energy dissipation, and hydraulic jump characteristics downstream of radial gates. Different 12 discharges were investigated, and their results were compared with previous physical results to verify the performance of the numerical results. The results obtained from the numerical model from all trials are almost identical to the physical model results. Five different alternative designs were carried out numerically to enhance the design of the New Assuit Barrage (NAB) spillway stilling basin. Results showed that alternatives 4 (changing the geometry of the basin by removing the end step and concrete slab) and 5 (as alternative 4 in addition to adding rounded baffle blocks presented in two rows arranged in a staggered way) gave good velocity distribution with low turbulence, low values of near-bed velocities, and stability of bed protection. Also, it is more economical because of the lower cost of concrete and excavation.

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Authors and Affiliations

Mohamed Elberry

Abdelazim Ali

Fahmy Abdelhaleem

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Amir Ibrahim

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Canadian International College (CIC), New Cairo Campus, 11835, 1 Khaled Ebn Elwaleed St, Zone (B), Cairo, Egypt
Hydraulics Research Institute (HRI), National Water Research Center, Cairo, Egypt
Benha University, Faculty of Engineering, Civil Engineering Department, Benha, Egypt

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Experimental and numerical investigation of scour downstream contracted spillways

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Numerical investigations of stilling basin efficiency downstream radial gates – A case study of New Assuit Barrage, Egypt

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Authors and Affiliations