Title: Controlling granular instabilities using fluidization

Author (Table Talk): Mario Ibrahim, Columbia University

Abstract:

Rayleigh-Taylor (RT) instabilities arise during granular chute flows where large, dense particles are imposed on small, less dense particles. Following the initially segregated configuration, particles are left to flow down an incline and RT plumes form during vertical mixing of the particles. Allowing the particles to flow farther yields a final segregated state, where the large, dense particles are beneath the small, less dense particles. Through numerical simulations of polydisperse granular chute flows, we observe the simultaneous formation of an additional granular instability, analogous to the Kelvin-Helmholtz (KH) instability in fluids, that is driven by shear between particle species. Further, we find that fluidizing the flow, by injecting air through the granular bed, may accelerate the onset of vertical mixing, and, in some cases, prevent the flow from achieving the final vertically segregated state.