Dilation, compression, and convection in granular shear experiments

Abstract

The flow of granular media in a liquid-like state is often dependent upon a competition between gravity and an external shear. As with granular gas experiments wherein the details of energy injection can affect the observed velocity fluctuations, the type of motion observed in dense granular flows often has subtle connections to the details of how the material is sheared and the geometry to which they are contained. A deeper understanding of how granular materials flow is thus dependent upon comparisons between experiments. Three separate experiments will be discussed that offer different roles for gravity and external shear in a circular geometry to examine the dynamics of granular media for both two-and three-dimensional flow. In the case of three-dimensional flow, a magnetic resonance imaging (MRI) resource has been utilized to investigate the motion of tracer particles within another granular species and data is obtained for different size and density ratios.