نوع مقاله : مقاله پژوهشی
نویسندگان
1
Department of Civil Engineering, Faculty of Engineering, Behbahan Khatam Alanbia University of Technology, Behbahan, Iran
2
civil engineering, Faculty of Technology and Engineering, Behbahan Khatam Alnabia Technology University
10.22034/nawee.2026.583195.1221
چکیده
Objective: To experimentally assess how regular, connected three-dimensional volumetric porosity modifies the hydrodynamic and morphodynamic response of a spur dike, and to compare a fully porous modular Chine dike and a three-row hybrid porous-shell configuration (3RC) with a conventional impermeable spur dike under submerged and non-submerged conditions.
Materials and Methods: Experiments were conducted in a 6.0 m long, 0.60 m wide recirculating flume at a flow depth of 0.15 m and discharge of 25.7 L/s. The approach flow was subcritical (U = 0.286 m/s, Fr approximately 0.23) and near the clear-water threshold (U/Uc = 0.96) over uniform non-cohesive sand with d50 = 1.2 mm. All dikes had a transverse length of 0.12 m. The Chine configuration was assembled from 2 x 2 x 2 cm cubic blocks with connected openings and a geometric volumetric porosity of approximately 0.25. Three-component velocities were measured using a Nortek Vectrino II ADV at 50 Hz for 120 s at each sampling node. Velocity records were despiked and filtered using correlation and SNR criteria. Each scour test continued for 24 h, and equilibrium bed topography was surveyed on a 1 x 1 cm grid with a laser profiler; dye and yarn tracers supported interpretation of the measured flow structures.
Results and Discussion: Regular volumetric porosity produced a controlled bleed flow through the dike body, relieved upstream stagnation pressure, weakened near-bed downflow, and reduced the concentration of high-vorticity cores near the structure. Under submerged conditions, porous configurations reduced peak near-bed downflow by about 50% relative to the solid case, while the fully porous Chine reduced peak vorticity at the dike by about 84%. Maximum equilibrium scour depth decreased from 9.3 cm for the solid dike to 7.1 cm for the fully porous Chine under submerged flow (23.7% reduction) and from 12.3 to 9.5 cm under non-submerged flow (22.8% reduction). The fully porous configuration also reduced scour-hole width and longitudinal extent and shifted the submerged deposition-bar onset from 23.2 to 14.95 cm, 35.6% closer to the structure. The 3RC case showed intermediate hydraulic and morphodynamic behavior.
Conclusion: A regular, hydraulically connected three-dimensional pore network can redistribute momentum through the structure, weaken coherent near-bed erosive motions, and reduce both scour depth and scour-hole extent. Within the tested conditions, the fully porous Chine configuration provided the most consistent scour mitigation, indicating that pore-network topology, in addition to overall permeability, is an important design variable for permeable river-training structures.
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