Effects of debris density and morphology on grate inlet clogging and drainage performance: A VOF-DEM study

Study Region: Urban road catchment areas with shallow-water drainage systems, where grate inlet clogging by floating debris frequently exacerbates flooding. Study Focus: This study employs a coupled Volume of Fluid-Discrete Element Method (VOF-DEM) model, validated by physical experiments, to simulate the transport and clogging behavior of three typical urban debris types—foam (300 kg/m³), leaves (1000 kg/m³), and plastic bags (1500 kg/m³)—under shallow-water drainage conditions. The objective is to investigate how material-specific properties (density and morphology) govern clogging dynamics and drainage performance. New Hydrological Insights for the Region: Results reveal that density governs movement patterns: low-density foam floats and migrates widely with minimal direct clogging; near-water-density leaves suspend and accumulate at grate gaps and corners; high-density plastic bags rapidly settle and cover the grate surface, reducing effective flow area. Morphology synergizes with density to enhance clogging stability. Clogging reduces drainage efficiency, with an average water level backwater of 3.2 mm and flow velocity reduction of 0–15.4%, showing spatial heterogeneity. This study establishes a multi-scale framework linking material properties to hydraulic response, providing quantitative references for anti-clogging grate design, targeted maintenance, and risk assessment of stormwater inlets in the study region. • VOF-DEM model examines float body traits' effect on clogging and drainage. • Low/high-density debris reduce flow via suspension or surface coverage. • Clogging impact varies spatially, most severe near outlets with water rise.