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

Elberry Mohamed, Ali Abdelazim, Abdelhaleem Fahmy, Ibrahim Amir

Journal of Water and Land Development

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2023

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no. 59

126--134

EN

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.

2

An experiment of energy dissipation on USBR IV stilling basin - Alternative in modification

Bantacut Alfiansyah Yulianur, Azmeri Azmeri, Jemi Faris Zahran, Ziana Ziana, Muslem Muslem

Journal of Water and Land Development

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2022

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no. 53

68--72

EN

Previous researchers have been widely studied the equation for calculating the energy dissipation in USBR Type IV, applied in the stilling basin structure as an energy dissipator. However, inefficient energy dissipating basins are commonly found in the field due to the large discharge and high water head, potentially damaging the bottom of the energy dissipating basin and its downstream river. Therefore, an energy dissipator plan fulfilling the safe specifications for the flow behaviour that occurred is required. This study aimed to determine the variation of the energy dissipators and evaluate their effect on the hydraulic jump and energy dissipation. For this purpose, a physical model was undertaken on the USBR Type IV spillway system. The novelty of this experiment showed that combination and modification dissipation features, such as floor elevation, end threshold and riprap lengthening, could effectively dissipate the impact of energy downstream. The final series exhibited a significantly higher Lj/y1 ratio, a favourable condition due to the compaction of the hydraulic jump. There was also a significant increase in the downstream tailwater depth (y2) during the jump formation. Therefore, the final series energy dissipator was better in the stilling basin design for hydraulic jump stability and compaction. The increase in energy dissipation for the final series type was the highest (98.4%) in Q2 and the lowest (84.8%) in Q10 compared to the original series. Therefore, this type can better reduce the cavitation risk damaging to the structure and downstream of the river.

3

Laboratory study of stilling basin using trapezoidal bed elements

Al-Fatlawi Thair J.M., Al-Mansori Nassrin J.H., Othman Nariman Y.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

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2020

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Vol. 29, No. 4

409--420

EN

When designing dam spillway structures, the most significant consideration is the energy dissipation arrangements. Different varieties of baffle blocks and stilling basins have been used in this context. However, the hydraulic jump form of stilling basin is considered to be the most suitable. The main objective of this research was to introduce four different baffle block shapes (models arranged from A to D, installed at slopes 0.00, 0.04, 0.06 and 0.08 in the stilling basins). To illustrate the consequences for the qualities of pressure-driven bounce, each model was attempted in the bowl. The trials applied Froude numbers between 6.5 and 9.2. The puzzle square model D provided the best outcomes compared to the models A, B, C and smooth. Model D with different models at inclines 0.00, 0.04, 0.06 and 0.08 was used to consider the impacts of perplex hinders on water driven-bounce when bed slants were changed. When the model D baffle used instead of a smooth bed at 0.08 slope, the reduction in y2 / y1 reached 12.8%, and Lj / y1 was 18.9%. Among the different bed slopes, a normal decrease in y2 / y1 ranged from approximately 10.3%, whereas the normal decrease in Lj / y1 was about 13.8% when the model D baffle was used instead of the model A baffle with a horizontal slope bed of 0.00. The results show that the new shapes led to a decrease in sequent profundity proportion and length of jump proportion; however, the energy dissipation proportion increased.

4

The impact of deepening the stilling basin on the characteristics of hydraulic jump

Siuta T.

Technical Transactions

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2018

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Vol. 115, iss. 3

173--186

EN

In this article, the results of computational fluid dynamic (CFD) modelling of the hydraulic jump conditions occurring in the experimental prismatic rectangular stilling basin with sudden crosswise expansion are presented. The FLOW 3D software program was used to numerically solve Reynolds Navier-Stokes (RANS) equations with the application of the k-ε turbulence model. The influence of the depth magnitude of the stilling basin and the ending sill installation on the hydraulic jump turbulent characteristics and submergence condition changes was investigated. Based on the results of the numerical modelling, it was found that various spatial flow processes contribute to the submergence condition of the hydraulic jump. These processes include: crosswise flow expansion within the stilling basin; local tail water surface level increase and total head loss due to vertical flow contraction; installation of the additional terminal sill. This contribution to the submergence condition allows a reduction in the required depth of the stilling basin, calculated on the basis of a one-dimensional simplified approach without consideration to the spatial characteristic of the hydraulic jump.

PL

W artykule przedstawiono przykład zastosowania techniki CFD (Numeryczna Mechanika Płynów) do modelowania warunków wystąpienia odskoku hydraulicznego w eksperymentalnej pryzmatycznej niecce wypadowej z nagłym poszerzeniem. W celu rozwiązania równań Reynolds Navier-Stokes (RANS) wraz z modelem turbulencji typu k-ε użyto programu FLOW 3D. Przedmiotem badania był wpływ głębokości niecki wypadowej i wysokości progu wylotowego na zmianę charakterystyki przepływu turbulentnego i warunki zatopienia odskoku. Na podstawie uzyskanych wyników modelowania stwierdzono, iż przestrzenne procesy przepływu, takie jak: poprzeczna ekspansja strumienia w niecce wypadowej, lokalne podniesienie poziomu zwierciadła wody dolnej na skutek kontrakcji pionowej przepływu w przekroju wyjściowym z niecki, instalacja progu wylotowego mogą przyczynić się w istotny sposób do zatopienia odskoku hydraulicznego, a tym samym pozwalają na redukcję wymaganej głębokości niecki wypadowej obliczanej na podstawie uproszczonej jednowymiarowej analizy przepływu bez uwzględnienia przestrzennego charakteru badanego odskoku hydraulicznego.

5

Długość odskoku hydraulicznego na modelu jazu

Urbański J.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

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2008

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Vol. 17, No. 1

3--12

EN

Results the investigation of length of submerged hydraulic jump are presented. Experiments were conducted on model taired construction with the outflow under the closure and with bottom stilling basins. Schema of investigated model and hydraulic parameters are typical for low head structures existing in the field. Measured length of hydraulic jump was compared with calculated according to different formulas. Relationships between nondimensional length of hydraulic jump λ0=L0/h1 with hydraulic parameters of flow q, v, Fr1 are calculated and compared with results of experiments.