Publication
Particle segregation is widespread in river channels and significantly influences bed grain size distribution. To date, most studies have investigated particle size segregation in straight river channels. Less studied is the case where particles segregate in meandering river channels with radial convection. To model this process, we conducted experiments by shearing bi-dispersed granular mixtures in an annular shear cell. Refractive-index matching (RIM) was used to visualize the bed’s inner structure. We reconstructed the particle spatial arrangement and three-dimensional particle velocity map from continuous series of image scans and Particle Tracking Velocimetry (PTV). In experiments, both axial and radial segregation was observed. Small particles tended to percolate downwards and accumulated radially to central regions, while large particles were squeezed upwards and gathered in outer regions. We observed logarithmic axial velocity profiles and radial particle convection from the three-dimensional velocity map. In the radial direction, bed height decreased while armor thickness increased, which led to a radially increasing segregation velocity. Sediment transport was estimated from particle spatial arrangement and corresponding particle velocity. We found that sediment transport was largest when the transport contribution from small particles matched that of large particles.