Design of Stilling Basin for Decreasing Back Water in the Dam Foot (original) (raw)
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Journal of Water Resource Engineering and Management, 2018
The water flowing over the spillway acquires a lot of kinetic energy by the time it reaches near the toe of the spillway. If precautionary measures are not made to dissipate this huge kinetic energy of water, large scale scour can take place on down stream side near the toe of dam and away from it. The kinetic energy of this supercritical flow can be dissipated by converting supercritical flow into subcritical flow by creating hydraulic jump. The phenomenon of hydraulic jump occurs, by providing stilling basin, end weir. Hydraulic jump type energy dissipaters are widely accepted techniques of energy dissipation while designing the hydraulic structures like dams, weirs and barrages. They are popular for their simplicity and efficiency, but have certain limitations when variations occur in discharge conditions. The energy dissipaters satisfactorily function at design discharge condition. But in case of varying discharges they are not efficient as the location of hydraulic jump tends to shift on apron. This would result in percentage reduction in energy dissipation. Therefore, it is necessary to address the issue of controlling the location of hydraulic jump and evolve a technique for the same. Local scour downstream of hydraulic structures due to hydraulic jump is considered one of the tedious and complicated problems facing their stability. This paper discusses the design of hydraulic jump type stilling basin for the overflow Spillway at Gunjwani dam. A model study is carried out by applying Froude’s model.
IRJET, 2022
A spillway is a crucial component of any dam project. The improper dam design is to blame for the failure of several dams. The planning and construction of the spillway should be done properly. The Himalayan region has recently developed orifice spillways. Since the efficacy of a gated overflow spillway depends on the depth of flow between the FRL and overflow crest elevation, only the widest practical gates are suitable. The incorporation of a breast wall enables orifice spillways, which combine the benefits of deeper flows over the crest with modestly sized gates. The dissipation of kinetic energy generated at the toe of the spillway is essential for bringing the flow velocity of the river back to normal in shortest distance. The energy dissipation arrangement is the most vital part and needs to be done carefully. However hydraulic jump type stilling basin found to be suitable for this project. In the present case an entire design of a spillway suitable to suit the typical site conditions has administered. Spillway has designed for maximum flood discharge of 15,800 m 3 /s.
Development of Stilling Basin Models with Appurtenances
International Journal of Engineering and Management Research
This research paper describes about the experimental work leading to the sustainable hydraulic structures by developing new stilling basin model as compared to USBR VI stilling basin model for pipe outlet using with sills. The experimental study was carried out for three Froude numbers namely 3.85, 2.85 and 1.85 for non-circular pipe outlet. Performance index (PI) has been used to evaluate the performance of stilling basin models tested using same sand base material and test run time. The scour pattern was measured for each test run and flow pattern was also observed. After 21 tests runs, it was found that the performance of stilling basin model improved even by reducing the length of basin from 8.4 d to 6 d by introducing intermediate sill of square cross section along with USBR VI impact wall and end sill. Performance of this model was found to be better than USBR VI impact basin for similar flow condition at reduced length of 6 d from 8.4d where d is the equivalent diameter o...
Numerical Modeling of Flow in USBR II Stilling Basin with End Adverse Slope
2019
Hydraulic jump is one of the effective ways of energy dissipation in stilling basins that the energy is highly dissipated by jumping. Adverse slope surface at the end stilling basin is caused to increase energy dissipation and stability of the hydraulic jump. In this study, the adverse slope has been added to end of United States Bureau of Reclamation (USBR) II stilling basin in hydraulic model of Nazloochay dam with scale 1:40, and flow simulated into stilling basin using Flow-3D software. The numerical model is verified by experimental data of water depth in stilling basin. Then, the parameters of water level profile, Froude Number, pressure, air entrainment and turbulent dissipation investigated for discharging 300 m<sup>3</sup>/s using K-Ɛ and Re-Normalization Group (RNG) turbulence models. The results showed a good agreement between numerical and experimental model as numerical model can be used to optimize of stilling basins.
NEW DESIGN OF STILLING BASIN MODEL WITH SQUARE SILL
Sustainable irrigation management system required efficient and economical design of stilling basin .The stilling basins are used to dissipate the energy of flowing water and protect the downstream structures like spillways, canals, etc. from the scouring. The aim of the present experimental investigation is to design the new stilling basin models for non circular pipe outlet using intermediate sill of square cross section. Performance of new stilling basin models were determined with performance index (PI), by operating the constant test run time of one hour and same base material downstream end sill. Increased values of PI indicate better performance of the stilling basin model. After experimentation with thirty test runs, it was found that when intermediate sill of square cross section is placed in suitable location in the stilling basin model, performance of basin improved significantly as compared to USBR VI impact basin model
Design of Hydraulic Jump Type Stilling Basin at Warana Canal
https://www.elixirpublishers.com/, 2015
Hydraulic jump type energy dissipaters are widely accepted methods of energy dissipation while designing the hydraulic structures like dams, weirs and barrages. They are popular for their simplicity and efficiency, but have certain limitations when there is variation in discharge conditions. The energy dissipaters satisfactorily function at design discharge condition. But in case of varying discharge conditions they are not efficient as the location of hydraulic jump tends to shift on apron. This would result in percentage reduction in energy dissipation and in turn damage hydraulic structures and adversely affect tail channel conditions. Therefore it is necessary to address the issue of controlling the location of hydraulic jump and evolve a new technique for the same. This paper discusses the design of hydraulic jump type stilling basin for the overflow weir of canal escape at Warana dam (India). It also throws light on the aspect of jump location and percentage energy dissipation. A physical model study is carried out by applying Froude’s model law.
International Journal on Engineering Technology (InJET), 2023
The difficulty of experimental methods to modify the complex model motivated the researchers to explore alternative solutions. Tanahu Hydropower Project is a storage-type hydropower project. It has an installed capacity of 140 MW and 140 m high concrete dam along with chute-type stilling basin followed by a complex topography. Computational fluid dynamic (CFD) model is a numerical approximation of partial differential equations. It has been widely used to simulate the fluid flow. In this study, a fluid flow is simulated through the stilling basin using the numerical model for different return period floods. The model's predictions for flow parameters are validated with the results taken from the 1:60 scaled physical models for the same project. The results regarding the flow velocities and water surface level are within 30% and 1.92 m accuracy respectively. The validated model is run for the three modification cases: i) by opening only two of the three spillway gates, ii) by decreasing the depth of the stilling basin, and iii) by decreasing the length of the basin, aiming to recommend the best alternative solution for the effective dissipation of the high kinetic energy of flow from the 140 m high dam. The results reveal that the base case model is the best solution compared to these three modified cases to pass the flood effectively. This study concludes that the CFD model is the effective alternative tool to analyze the fluid flow problems even in the complex geometry and is recommended to use for the design and modification processes.
New Perspectives on the Design of Stilling Basins
B P International, 2024
In the design of hydraulic structures, the velocity of water flow should be maintained at acceptable levels. The high velocity of water in an earthen channel or a natural river causes erosion of the channel bed and walls, which may cause irreparable damage to the facilities adjacent to the river. Also, in many cases, factors such as the steep slope of the channel floor, the large energy difference between two sections, the free fall of water, or the kinetic energy of the water flow is more than expected. This inevitably requires designing structures to reduce the kinetic energy. Such hydraulic facilities are called energy dissipater structures. Different types of energy dissipaters are available, the most common of which are stilling basins. In some way, the flow is depleted due to the hydraulic jump and the creation of strong turbulence in the stilling basin. For a better understanding of the energy available in the water velocity at the toe of the spillway, we can refer to the Grand Coulee dam. This dam is built on the Columbia River in America. The designed discharge of the dam spillway is 28320 m3/s and the water level upstream and downstream for this discharge is 393.8 and 308.23 m, respectively. If it is assumed that the energy loss on the spillway is insignificant, the energy of the water downstream of the spillway is equal to 23 GW according to the relation E=ρgQH, where H is the difference in water level between the upstream and downstream sections. If the energy is not restrained properly, even the best conditioned downstream stone protection will undergo severe erosion. The design and construction of stilling basins in the downstream of dam spillways is one of the most common methods of water energy control, which is the subject of this study.