The transport of solid particles as bed load by a fluid flow is widely encountered in industrial and environmental applications. For example, it can be found in rivers, oceans, petroleum pipelines, sewer systems, and dredging lines. Bed load transport is a kind of dense granular flow and it is known to segregate grains by size and by shape. Understanding the dynamics between the granular material and the fluid remains challenging. Therefore, the problem is still open. This project proposes an experimental study of the influence of particle shape on bed load transport by a laminar flow. The experiments will be carried out in a laboratory flume with a granular bed composed of sediments of bimodal shape. For this, we shall form a bed consisting of PMMA beads mixed with PMMA particles of other shapes (disks or cubes), and submit it to a laminar-shear flow. We shall use refractive-index-matching to track particles' motion and determine the local rheology from the surface to deep inside the bed. The individual motion of particles will be filmed with a digital camera and numerical codes will be developed to post-process the images. Therefore, the objectives of this project are to better understand how the presence of two different shapes in the bed can modify the velocity profiles of grains along the height of the granular bed, as well as explore the mechanisms of segregation for this specific problem. This work will be developed in the research group of Professor Douglas J. Jerolmack (PennSed Group) at the University of Pennsylvania. Professor Douglas J. Jerolmack has a renowned experience in experimental geophysics, with a focus on geomorphology, including the physics of fluid-driven (water and wind) sediment transport; landform dynamics; stochastic and nonlinear transport processes; and landscape response to dynamic boundary conditions such as climate.
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