Author(s): Pankaj Singh; Dhrubajyoti Sen

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Keywords: Scour; Energy dissipation; End-sill; Turbulent Kinetic Energy

Abstract: Hydraulic jump stilling basins are widely used in the spillways of dams and barrages for dissipating some of the flow's energy as it passes through the structure. Weirs used in practical engineering in India are equipped with a downstream stilling basin, followed by a secondary apron made of an arrangement of concrete blocks. The present study investigates the hydraulics of jumps occurring over the stilling basin for possible ways to reduce scour in the mobile bed downstream of the secondary apron. Experiments are carried out in one of the flumes at the hydraulics laboratory of IIT Kharagpur, India. The experiments examine the scour extent for different heights of the end-sill, located at the downstream edge of the stilling basin, along with the measurement of velocity at the end of the secondary apron using an Acoustic Doppler Velocimeter (ADV). The presence of an end-sill reduces the scour downstream of the apron; however, beyond a limiting height of the sill, the results show a reverse trend with an increase in scour. The near-bed turbulent kinetic energy (TKE) is higher for a stilling basin without an end-sill, which decreases for a model end-sill height of 12 mm. However, a higher end-sill height creates a flow separation and recirculation zone downstream of the stilling basin, which intensifies the near-bed turbulence, and leads to an increase in scour. The maximum scour depths obtained are correlated with the near-bed TKE-s for both free and submerged flows, suggesting that an intermediate sill height (12 mm) is optimal in reducing scour downstream of the experimental apron.

DOI: https://doi.org/10.64697/978-90-835589-7-4_41WC-P2064-cd

Year: 2025