CFD Analysis of Hybrid Spur Dike Field for Enhanced Flood Carrying Capacity of Rivers

ABSTRACT This study numerically investigates the three‐dimensional flow characteristics within a hybrid spur dike field to evaluate how alternating impermeable (I) and pile (P) spur dikes influence channel hydraulics and sediment transport potential. Using ANSYS Fluent with the standard k − ε model, six geometric configurations (each maintaining identical first and last impermeable spur dikes) and three discharges were simulated to analyze the effects of permeability ratio and spatial arrangement on internal circulation and velocity distribution. Results show that impermeable spur‐dike field systems generate a single compact recirculation cell extending over approximately 4–5 m, with near‐bank velocity reductions exceeding 70%, leading to strong stagnation and sediment‐deposition potential. In contrast, hybrid configurations (particularly the balanced 3I‐2P and fully hybridized 4I‐3P layouts) develop multiple smaller vortices that enhance shear‐layer instability and fluid exchange between the main flow and the inner zone. The 4I‐3P configuration achieved the most favorable hydraulic performance, shortening the reattachment length to 3.3 m (50% reduction relative to the impermeable case) and increasing near‐bank velocities to 0.12–0.15 m s −1 . These results indicate a 40%–65% improvement in momentum redistribution and a 60% reduction in stagnation area compared to impermeable layouts. Overall, the findings demonstrate that an equal or well‐distributed combination of impermeable and pile spur dikes provides the optimal balance between flow conveyance and morphological stability. The proposed hybrid system offers a hydraulically efficient and sustainable approach for enhancing flood‐carrying capacity and reducing sediment accumulation in long river reaches.