2022 CSDMS meeting-106

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Role of fluid-drag force and particle interactions on shape-induced segregation in sediment transport

Fernando David Cúñez, University of Rochester Rochester New York, United States. fcunezbe@ur.rochester.edu
Rachel Glade, University of Rochester Rochester New York, United States. rachel.glade@rochester.edu

Fluid-driven granular flows sculpt Earth's surface through processes such as soil creep, landslides and debris flows, and river bed-load and suspended sediment transport. In the case of river bed-load transport, grains may move by rolling, sliding, and jumping within a thin layer known as bed-load layer. In this layer, it is common for grains to segregate by size (a process that has been extensively studied) or shape, which has only recently been recognized as an important control. Here we perform numerical simulations to examine how shape-driven particle segregation is controlled by 1) purely granular interactions and 2) fluid-granular dynamics. To isolate granular dynamics, we construct a DEM model using LIGGGHTS to examine segregation of dry grains of different shapes in a rotating drum. To fold in the role of fluid drag, we use a CFD-DEM model (OpenFOAM + LIGGGHTS) to study particle segregation in open channel laminar flow. To efficiently simulate different shapes, we use bonded spherical particles to construct spheres, cubes, and cylinders. For the former, we use a horizontal cylinder filled with the same particles, and rotate it at low angular velocities. Meanwhile, for the latter, we set a periodic channel filled with spherical and non-spherical particles, of equal mean volume, sheared by a viscous Couette flow which imposes enough shear stress to move the particles by bed-load transport. For both, we investigate the statistical properties of the segregation by size and shape that non-spherical grains experience in the systems by tracking hundreds of individual trajectories throughout the entire bed, and the mechanisms involved that are mainly driven by particle collisions and fluid-grain interactions. These results illuminate the role of grain shape in controlling sediment transport, with implications for natural rivers, hillslopes, and aeolian systems.