Author(s): Z. Ahmad

Linked Author(s): Ahmad Zia Rafat

Keywords: Dam; Overflow spillway; Under sluice spillway; Physical modelling; Stilling basin; Cavitation

Abstract: Physical model study of spilling arrangement of the dam of Malana-II hydroelectric project has been carried out to ensure the safety of the dam. The discharging capacity of the under sluice spillways and an overflow spillway has been studied under their individual and joint operations. Cavitation index of the flow over the spillway surface has also been estimated to ensure cavitation free flow. Initial proposal of provision of flip bucket for energy dissipation of flow through overflow spillway has been replaced by hydraulic jump type stilling basin by pooling the water by a submerged weir. The discharging capacity of joint operation of both the under sluice spillways was lower than the summation of discharges under their operation in isolation, which can be attributed to interference of their zone of influence at inlet. Negligible cavitation was found in the flow of overflow spillway. Flow onwards to the toe of the overflow spillway was chaotic and full of strong cross-currents. The flip bucket was also not performing well due to rise in depth of flow and mixed directional flow as a result of cross-currents upstream of the bucket. For the facilitation of energy dissipation, flip bucket arrangement was replaced with hydraulic jump type stilling basin by pooling the water with provision of a submerged broad crested weir with steps downstream of the weir. Knowledge gathered from this model study shall be useful for the design of such type of the structures in future.

DOI: https://doi.org/10.15142/T35934

Year: 2018