Influence of submerged channel obstructions on flow patterns, turbulence, and bed morphology under ice cover - experimental study and numerical simulation

This dissertation explores the complex interactions between submerged angled spur dikes, rigid leafless vegetation, and ice cover in cold-region rivers, focusing on understanding their effects on flow dynamics, sediment transport, and scour formation. The research addresses a significant gap in existing knowledge by examining these interactions under various flow conditions, including open channel and ice-covered scenarios, through large-scale flume experiments and advanced numerical simulations. The study first investigates the influence of spur dike orientation, submergence level, and ice cover roughness on local scour depth and flow patterns. Results reveal that larger dike alignment angles (greater than 90°) reduce scour depth, while rough ice cover exacerbates scouring compared to smooth ice conditions. The research highlights the critical role of dike orientation and ice roughness in designing hydraulic structures to minimize erosion and protect riverbanks. Building on these findings, the second part of the study focuses on the turbulent flow structures around submerged angled spur dikes under ice cover. Quadrant analysis indicates that ice cover intensifies turbulence, mainly through increased ejection and sweep events near the dike tip, leading to more significant sediment mobilization and scour. The research emphasizes the importance of considering ice-covered flow dynamics in river engineering, especially in cold regions where ice significantly alters flow behavior. The final component of the dissertation examines the hydrodynamic characteristics within vegetated pools under ice cover representing regional obstruction to the flow field, emphasizing the role of vegetation configuration on flow modification. The study demonstrates that vegetation, particularly in staggered configurations, effectively reduces flow velocity and enhances sediment deposition, creating favorable conditions for aquatic habitats. However, ice cover introduces additional complexity by altering the velocity profiles and turbulence distribution, with implications for river management and restoration efforts. The findings of this research provide valuable insights into the design and implementation of river management strategies in cold climates. The study’s outcomes have practical applications in optimizing spur dike configurations, enhancing the effectiveness of vegetated riverbank stabilization, and improving the resilience of river ecosystems to ice-related challenges. Future research should further explore the synergistic effects of spur dikes and vegetation, integrate more diverse vegetation models, and validate these findings in natural river systems under varying climatic conditions.