Hydraulics of Perforated Riser Inlets for Underground-Outlet Terraces
ABSTRACT Ageneral depth-discharge relationship for perforated riser inlets with bottom orifices is derived from basic principles. An idealized pressure distribution inside the riser is the key simplifying assumption. The shape of the depth-discharge curve depends upon the values of two nondimensional parameters. To assess the validity of the theoretical relationships, depth-discharge data for nine riser-inlet configurations were measured in the laboratory. The theoretical depth-discharge curves for these nine configurations fit the experimental data very closely. Three guidelines for designing hydraulically efficient riser inlets are: (a) the total side-orifice area should be large relative to the bottom-orifice area; (b) the side orifices should be concentrated near the bottom of the riser; and (c) the bottom orifice plate should be installed as far below the side orifices as is feasible