Title: Sediment transport and channelization in rivers and fractures

Author (Invited): Arshad Kudrolli, Clark University

Abstract:

We discuss a series of experiments towards developing an understanding of the physical processes important to sediment transport and erosion. We begin by focusing on a single grain at rest on a rough surface in a fluid flow, and discuss the shear stress required to dislodge the grain as a function of its properties and flow conditions. We then consider a granular bed which is sheared by a fluid flow and discuss the depth resolved granular transport that develops as a function of applied shear stress using refractive index matching techniques. We then compare and contrast the observed motion of the fluid and granular motion with forms derived from granular and suspension rheology. Finally, we discuss patterns that develop in a fracture filled with grains due to coupling of fluid flow and erosion. We demonstrate that channels form which grow upstream due to a convergence of fluid flow similar to those observed in curvature driven seepage erosion systems. We discuss a multiscale model which uses a statistical physics approach to capture the overall evolution of porosity in the experiments.