Author(s): Goncalo Cardoso; Ines Meireles; Jorge Matos
Linked Author(s): Jorge Matos
Keywords: Baffle stilling basin; Stepped spillway; Hydraulic jump; Pressure head
Abstract: Among the large variety of existing energy dissipators, stilling basins are commonly used downstream of conventional or stepped spillways. An experimental study was conducted on a stilling basin downstream of a large-scale stepped chute assembled at the National Laboratory of Civil Engineering (LNEC), Lisbon. In the present paper, new data are presented on the development of the pressure head along stilling basins both without and with appurtenances, namely baffle blocks and end sill designed according to the USBR Type III basin. The results show that the presence of appurtenances influences the pressure head along the basin, with exception on the impact flow region, for identical location of the upstream hydraulic jump section. Near the downstream end of the jump, a reduction of 20% on the pressured head was observed in the baffle basin, against the values obtained without appurtenances. Empirical formulae are presented for predicting the pressure head values along both types of stilling basins. A comparative analysis on the length of the hydraulic jump on basins with and without appurtenances is included. The improvement on the performance of the baffle basin compared to that of the basin without appurtenances is fairly similar to that obtained when comparing USBR Type III and Type I basins.