Experimental investigation of a vortex-flow restrictor: Rain-blocker performance tests

Flow restrictors, or rain blockers, are commonly used at inlets of storm-drain networks to limit the peak flow entering storm sewers. This reduces the likelihood of the sewer system becoming hydraulically overloaded, thus preventing sewer backups and residential flooding. The vortex-flow restrictor limits flow by forcing flow through a helicoidal chamber followed by sudden expansions and contractions that create high levels of turbulence. The high turbulence produced in a vortex-flow restrictor limits flow rates much more than a simple orifice, while maintaining a relatively large flow opening that can reduce the chances of clogging. Hydraulic tests were conducted with a vortex-flow restrictor (FR Type I) as well as a modified version in which the vortex chamber was removed (FR Type II), in which case the restrictor works a simple orifice plate. Discharge coefficients were calculated for the tested flow restrictor configurations and were compared to the case in which no flow restrictor was in place.