Sediment Erosion And Deposition In The Wake Flow Of Flexible Vegetation*

Sediment erosion and deposition downstream of thin rectangular flexible plates mimicking aquatic vegetations with aspect ratios ranging from 5 to 15, and width-based Reynolds numbers ranging from 2500 to 3900 were experimentally investigated. The sediment bedform and topography were characterized using a high-resolution surface scanner whose data was later utilized to calculate net erosion volume. The impacts of wake flow dynamics on sediment erosion patterns were further illustrated using time-resolved Three-dimensional Particle Image Velocimetry (3D-PIV). The results indicate that enhanced local turbulent intensities due to the presence of flexible plates caused sediment erosion right downstream of the obstacles. Sediment erosion rate was highly influenced by both aspect ratio and Reynolds numbers. Specifically, the growth of Reynolds number resulted in increased erosion rates. However, the trend was opposite with the growth of plate aspect ratio. Further investigation of three-dimensional flow statistics highlighted that higher aspect ratio led to larger Cauchy number and inclination angles at the base of flexible plates, which was accompanied with lower turbulent kinetic energy levels and therefore mitigated local sediment erosion.