Effects of anti-vortex plates on air entrainment by free vortex

Free surface vortex and air entrainment are not favorable experiences in hydropower and pumping projects. While complete omission of vortex and air entrainment is not always cost effective, partially weakened free-surface vortex flow is more economical and practical. Hence, in this study, a comprehensive set of experiments were conducted to partially reduce vortex strength and air entrainment at vertical pipe intakes, using rectangular anti-vortex plates. This phenomenon results in increasing water discharge compared with a corresponding free-surface vortex for the same water depth, i.e. in cases of shaft spillway. The plates were used as singles and in pairs and placed symmetrically and asymmetrically, with respect to the pipe axis. Accordingly, the results of partially entrained air using anti-vortex plates were presented as graphs and practical equations. Finally, design guides and recommendations were provided to predict the effects of plate geometries and positions on free-surface vortex strength.