Introduction
Sediment flushing is a significant phenomenon in hydraulic engineering, influencing both river morphology and environmental stability downstream of diversion dam. Experimental studies in this domain are often costly and time-consuming. Consequently, numerical modeling has emerged as a practical and efficient method for analyzing sediment transport processes. This study focuses on modeling the impact of varying channel slopes and gate openings on sediment bed evolution in sediment slice canals of diversion dams using Flow-3D software.
Methodology
The study utilized experimental data from a laboratory flume at the University of Tehran to calibrate the numerical model. The flume, measuring 2.5 m in length, 0.16 m in width, and 0.35 m in height, featured a centrally positioned vertical sluice gate. Sediment material consisted of uniform sand particles with a mean diameter of 3.5 mm. Simulations were performed using the Volume of Fluid (VOF) method in Flow-3D, applying different gate openings (25%, 50%, 100%) and channel slopes (5%, 10%, 15%). Three turbulence models (RNG, k-ε, and LES) were tested, and the RNG model was selected due to its better agreement with experimental results.
Results and Discussion
Simulation results revealed that reduced gate openings led to increased scour depth and more pronounced formation of sediment mounds downstream. The sediment bed profile exhibited minimal variation beyond 70% gate opening. Moreover, increasing the channel slope resulted in greater scour depth near the gate and sequential sediment mound formation further downstream. The RNG turbulence model achieved a calibration error of only 3.4%, outperforming the other models. Temporal analysis indicated that sediment transport and profile formation occurred rapidly after gate opening, but profile changes were less significant beyond 0.6 seconds, suggesting that time was a secondary factor compared to slope and gate opening.
Conclusion
The study demonstrates that numerical modeling using Flow-3D with the RNG turbulence model provides a reliable approach for simulating sediment bed evolution downstream of sediment flushing structures. Gate opening and channel slope significantly influence the depth and pattern of sediment scour. For gate openings exceeding 70%, further increases have negligible effects. These findings can inform future designs of sediment flushing systems and support the development of optimized hydraulic structures in irrigation and water distribution networks.