Hydraulic Jump in Stilling Basins with Perforated and Continuous Sills

Kinetic energy of the water over large spillways should be dissipated in the stilling basins by generation of a hydraulic jump in order to prevent scouring of riverbed and damaging the downstream structures. There are many types of stilling basins, and the most popular ones in practice are the standard USBR basins. The purpose of this study is to evaluate the behavior of perforated and continuous sills in stilling basin as well as their effects on the characteristics of a hydraulic jump including jump length and relative dissipated energy. Results of experiments indicate that the perforated sill, in comparison with the continuous one, has a better behavior in controlling and stabilization of hydraulic jump within the stilling basin which increases the energy dissipation and reduces the jump length. Furthermore, the results show that the perforated sill with 50% opening reduces the basin length about 61% of the required basin length for a free hydraulic jump. Moreover, perforated sill basins are able to dissipate 60% of the inflow energy at Froude number 4.5, while dissipation of energy increases to 90% at Froude number 12.