Determination of critical submergence depth at horizontal intakes

Haspolat, Emre
The purpose of the study is to investigate the formation of air entraining vortices under both symmetrical and asymmetrical approach flow conditions in an experimental setup of a horizontal water intake structure composed of a reservoir-pipe system. To determine at which critical submergence the air entraining vortices forming; a series of experiments were conducted in the experimental setup with horizontal pipes of four different diameters. Approach channel side walls of the intake structure model are adjustable to create either symmetrical or asymmetrical approach flow towards the intake. Based on dimensional analysis, a dimensionless equation for the critical submergence was derived as a function of related hydraulic and geometric parameters. Empirical equations were derived for the critical submergence by using regression analysis and they were compared with similar ones available in the literature. Model scale effects on the values of experimentally measured critical submergence data were investigated and it was shown that neglecting some of the important flow parameters in the application of model laws causes significant variations on the values of critical submergence. To eliminate the formation of air-entraining vortices in front of the intake structure floating rafts of various dimensions were tested as anti-vortex devices and very succesful results were obtained.