Segregation in Bimodal Contact/Combined Load: Tilting-Flume Study

In this contribution, the effects of solids segregation on intense transport of solids and bed friction in a laboratory flume are evaluated by comparing bimodal solids flows with the corresponding flows of unimodal solids. The comparison is carried out for two types of solids transport: contact-load transport and combined-load transport. Experiments with intense transport of bimodal solids mixtures composed of two solids fractions that differ primarily in particle size showed a process of vertical sorting, resulting in partial segregation of the fractions in a flume. The segregation affected a layered structure of flow above the plane surface of an eroded bed. Lightweight solids fractions of different colors were used in the experiments to enable clear visual observation of the segregation. Measurements of integral quantities of steady, uniform solid-liquid flow were used to quantify solids transport parameters and bed friction parameters. The observed segregation patterns differ for the two types of solids transport and so differ their effects on solids discharge and bed friction coefficient in flows of the two bimodal mixtures.