127 / 2025-07-16 14:09:06

Turbulence-Driven Particle Kinematics in Bedload Transport: A CFD-DEM Study

Bedload transport governs sediment flux in riverine and engineered systems through turbulence-modulated interactions between near-bed coherent structures and granular particles. Despite foundational advances by pioneers like Einstein and Bagnold, predictive models exhibit persistent discrepancies against field data due to unresolved turbulence-particle coupling at the grain scale. This study employs a coupled Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) framework to resolve turbulence effects on particle kinematics across subcritical to supercritical Shields regimes. Simulations capture: (1) Turbulence-driven particle entrainment initiating below the critical Shields threshold via intermittent sweeps and ejections; (2) Bedform evolution from small-scale ripples to dunes linked to turbulent kinetic energy anisotropy; (3) Particle saltation dynamics (trajectory geometry, rest periods, collision statistics) modulated by near-bed turbulence intensity. Quantitative analysis reveals that turbulence fluctuations affect particle-scale mobilization thresholds and transport intermittency. These results establish a mechanistic link between microscale turbulence structures and bulk sediment flux, providing a physics-based framework to refine predictive models through explicit incorporation of turbulence-particle phase interactions.