Author(s): M. J. Ostadmirza; A. R. Zarrati; R. Roshan; Kh. Safavi
Linked Author(s):
Keywords: Cavitation; High speed flows; Tunnels; Annular aerators; Air concentration; Effective length
Abstract: Aerators are constructed in high speed flows to prevent cavitation attack. Although horseshoe or circular tunnel sections can be converted to rectangular shape to use aerators similar to chute spillways, such a solution needs expensive subsequent concrete operation. Alternatively, annular aerators could be constructed which fit well with the tunnel section. There is however no information for design of annular aerators available in the literature. In the present study different annular aerator sizes were tested in a large physical model of a bottom outlet 40 m long and 0.38 m in diameter. Flow discahrge and depth as well as air concentration near the tunnel invert were measured to compare different aerators' performance. Each aerator was tested at different flow discharges and upstream gate openings. Experiments showed that the aerator shape should follow the tunnel section. The effect of aerator geometry and flow condition on air concentration reduction in deaeration zone was also found in these experiments. Based on experimental data an empirical equation was also developed for the effective length of annular aerators.
Year: 2011