Unraveling erosive mechanisms in curved river channels: Insights from a controlled 180° meander experiment
摘要
Riverbank erosion in meandering channels is a complex process driven by hydrodynamic forces, turbulence, and sediment properties. This study investigates cohesive bank erosion mechanisms in a 180° meandering channel under controlled laboratory conditions. Using flume experiments at four different Reynolds numbers (1.0x104, 2.0x104, 3.0x104 and 6.0x104), the study examines undercut height, depth, and length evolution over time, emphasizing the role of turbulence, secondary circulation, and shear stress variations. Results indicate that erosion follows a two-phase mechanism: an initial rapid sediment detachment phase, driven by high shear stress and turbulence intensities, followed by an equilibrium phase where erosion stabilizes. Maximum erosion occurs between 60° and 90° of the meander bend, where secondary currents amplify shear stress along the outer bank. Reynolds shear stress (RSS) and turbulent kinetic energy (TKE) peak at the bank toe, confirming the role of curvature-induced secondary flow in sediment entrainment. This study provides critical insights into near-bank turbulence dynamics, showing that flow separation, recirculation, and helical flow structures significantly influence undercut elongation and widening. These insights contribute to sustainable sediment management and erosion mitigation, essential for protecting riverbanks, floodplains, and infrastructure in meandering river systems.
Research highlightsControlled flume study captures erosion dynamics in a 180° meandering channel. Undercut initiation shifts downstream with increasing Reynolds number flow. Peak shear stress and TKE at 90° confirm curvature-driven sediment detachment. Integrated ADV and visual tools track undercut growth across angular positions. Erosion transitions from particle-scale to mass failure with rising turbulence.