Shear dispersion in dense granular flows

What is it about?

The dispersal of a contaminant in a pipe flow is a classical fluid phenomenon. In the early 20th century, G. I. Taylor showed that, at long times and far downstream from the injection point, the process can be described by an averaged description in which contaminant is advected by the mean flow and diffuses with an effective diffusivity that is inversely proportional to the solute's molecular diffusivity. This paper extends Taylor's calculation to the rapid flow of dry cohesionless powders (granular materials) down an incline.

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Why is it important?

Understanding dispersal of particles in flow is relevant for industrial separation processes such as the drying of powders for the purposes of dehydrating food. Such processes also determine the distribution of debris upon the cessation of an avalanche or landslide, which can dictate the ecological impact of the geological event. This paper introduced the first mathematical theory of granular dispersion and provided specific analytical results and scaling laws to help guide practical research.