The impact of bar grate clogging on the discharge capacity of stormwater inlets in broad-crested weir mode

Grate inlets are crucial to urban stormwater drainage, influencing network efficiency and flood risk. Previous studies lack data on discharge capacity and coefficients of sump inlets under clogging conditions. This study experimentally investigates the hydraulic characteristics of sump grate inlets under varying degrees of clogging in the broad-crested weir (BCW) mode. The results show that the discharge coefficient in BCW mode Cw remains relatively stable, averaging 0.858 ± 7% across a wide range of clogging conditions, with a perimeter contraction coefficient ranging from 0.178 to 1. Additionally, a clear functional relationship between the discharge coefficient Cw and the Froude number Frw was obtained. This relationship enables a quantitative assessment of the sum of kinetic energy coefficient and the equivalent coefficient of hydraulic resistance of the inlet. These findings provide some insights for the design and modelling of stormwater sump grate inlets in weir mode, taking into account clogging effects.