Author(s): Yesheng Lu; Nian-Sheng Cheng; Olivier Eiff
Linked Author(s): Olivier Eiff
Keywords: Turbulence; Vegetation; Bed roughness; Open channel flows
Abstract: Vegetation-turbulence interactions in open channels critically influence sediment transport, pollutant dispersion, and flood resilience. While vegetation-induced drag and turbulence modulation are well-documented, the combined effects of vegetation and bed roughness on near-bed turbulence remain poorly understood—a significant knowledge gap given its implications for riverine processes. Recent studies emphasize vegetation's role in reshaping near-bed boundary layers, yet most research focuses on smooth beds, neglecting natural roughness. The interplay between roughness elements and vegetation in modulating near-bed boundary layer characteristics—particularly velocity gradients, Reynolds shear stress, and turbulent kinetic energy—remains unresolved. This study addresses this gap by investigating bed roughness effects on turbulence structures in emergent vegetated flows. High-resolution PIV measurements were conducted under three bed conditions: smooth and rough beds with sediment diameters of 1.78 mm and 3.30 mm. Spatial distributions of mean velocity, Reynolds shear stress, and turbulent kinetic energy were analyzed, complemented by quadrant analysis to elucidate roughness-driven momentum transport mechanisms.
Year: 2025