Research
Erosion of Granular Beds by Shear Flows
Fluids in the natural world invariably flow over boundaries. In many cases, these surfaces are not simple rigid bodies; instead, they are complex granular materials. Examples include soils, sand, or sediment deposits. For such weakly cohesive materials, strong shear flows can significantly modify the boundary topography by entraining bed material. These changes can then feed back on the flow, leading to very complex behavior and the formation of fascinating large-scale landscapes. Erosion by strong fluid flows can also lead to signficant hazards, and so better approaches to erosion control would have important practical applications.
Current models of the entrainment of bed material by shear flows are crude and empirical, since the problem is tremendously complex. In collaboration with Corey O'Hern at Yale and Mark Shattuck at City College of New York, we are working to understand the erosion process in detail by combining measurements of the internal structure of the granular bed, the fluctuating flow field and wall shear stresses, and the evolution of the large-scale topography. By also performing detailed numerical simulations, we hope to shed new light on this old, difficult problem.
Representative Publications
A. H. Clark, M. D. Shattuck, N. T. Ouellette, and C. S. O'Hern, "Onset and cessation of motion in hydrodynamically sheared granular beds," Phys. Rev. E 92, 042202 (2015).