Hydraulic capacity of a grate inlet in supercritical flow: weir equation

Studies on the hydraulics of urban storm inlets have relied on dimensional analysis and numerical models to represent the capture process of grates using empirical equations. Because of the test hypotheses and proposed applications, various formulations generate scattered knowledge that is difficult to compare. The experiments of three grates at full scale (1:1) are reanalyzed, with total flows ranging from 10 to 81 l/s, transversal slopes ranging from 0.7% to 3%, and longitudinal slopes ranging from 2% to 8% to better understand the catchment of urban grate inlets. The traditional weir equation has been properly adjusted, with the hydraulic head, such as the flow velocity and depth head, as well as the discharge coefficient varying between 0.05 and 0.232, depending on the Froude number of the approaching flow.