Hydrograph-based investigation of scour reduction using baffles at circular culvert outlets with inlet obstruction effects

This study evaluated downstream scour at circular culvert outlets using experimental observations and validated numerical simulations. Two discharge hydrographs with peak flow rates of 13.8 l/s and 20 l/s were analyzed under inlet blockage levels of 0%, 25%, and 50%. The Renormalization Group (RNG) turbulence model was calibrated and validated against measured scour data, and ten downstream baffle configurations were tested under steady and unsteady flow conditions. Results showed that baffles significantly reduced scour depth in all cases. Under steady flow, scour reductions ranged from 14.77% to 18.44%, depending on discharge and blockage level. Under unsteady flow, reductions ranged from 25% to 49.32%, with the greatest improvement observed for the higher discharge hydrograph. Although the numerical model slightly overestimated scour depth, it showed good agreement with experimental measurements. The results demonstrate that downstream baffles are an effective measure for mitigating scour and enhancing the hydraulic performance and resilience of circular culvert systems.