Size distributions in suspension over sand–pebble mixture: An experimental approach

Experiments were conducted in a laboratory flume to estimate the grain size distributions in suspension at different heights over five heterogeneous sediment beds of different values of bed roughness. The analysis had been performed to study the influences of velocity, bed roughness and ripple height on the size sorting, which developed the specific grain-size distribution in suspension. The observed size distributions in suspension were tested using three statistical distributions, such as, log-normal, log-hyperbolic and log-skew-Laplace. Tests indicated that log-hyperbolic distribution does not fit in suspension; even the original beds' grain size distributions were log-hyperbolic. It is observed from the experimental findings that the flow velocity influences the overall grain size distribution leading from log-normal to log-skew-Laplace distribution with the increase of velocity, but the bed roughness does not have any role in changing the size distribution from log-normality. The results of this study would be valuable to hydraulic engineers and sedimentologists to predict the nature of bed material from the size distributions of suspended materials.