Multi-parameter evaluation for optimizing spur dike spacing in river engineering

This study identifies the spacing threshold for hydraulic independence between two emerged impermeable spur dikes using validated computational fluid dynamics modeling. Numerical simulations analyzed velocity, turbulent kinetic energy (TKE), turbulence intensity (TI), and wall shear stress (WSS) across discharges (0.0336-0.2352 m³/s) and spacings (1-6 m). The results demonstrate that smaller spacings (<5 m) induce strong interactions. The downstream spur dike experiences a 25%-40% velocity reduction due to upstream shielding, while its TKE exceeds upstream values by 30%-50%. A critical threshold of 5-6 m emerges, beyond which tip velocities converge, TKE and TI disparities stabilize, and hydraulic independence is achieved. Increasing discharge amplifies turbulence magnitude but does not alter this threshold. Spacings below 5 m create merged wake zones, elevating local WSS by up to 45% compared to the widest spacing case (6 m), thereby increasing scour risk, while spacings above 5-6 m limit WSS concentrations to <10% of peak values. The novelty of this work lies in applying a multi-parameter evaluation framework (velocity, TKE, TI, and WSS) to define independence more rigorously than single-parameter studies, and in identifying the progressive transition from strong interaction to full independence. This approach provides both theoretical insight and practical design guidance for spur dike spacing optimization.