Alban Sauret (Multiphase & Multiscale Flow Laboratory, University of California Santa Barbara, USA). Dry to wet transition and cohesive effects in granular flows.

Over the past decades, many rheological models have been developed to describe the flow of dry granular media and suspensions. Yet, many configurations, such as the transition from an initially dry granular material to a suspension, or the cohesive effects in powder flows are not captured through this approach.

I will first present our recent efforts to model the transition from dry grains to a particulate suspension when particles are poured in a liquid. This situation controls a variety of processes, from industrial blending to tsunami generation by landslides. Modeling is, therefore, critical to mixing optimization and natural hazard assessment, but the transition between the two regimes remains elusive.

I will then discuss the influence of cohesion in granular flows. Cohesive effects in powders (cement, pharmaceutical powders, or flours) modify the overall flow of grains. Using a Cohesion Controlled Granular Material, we consider the collapse of a column made of cohesive grains. This configuration has been extensively studied in the case of dry granular material and allows us to probe the influence of the inter-particles cohesive forces on the macroscopic flow.