Identification of the solid and fluid regimes of a granular medium

Abstract

We performed experiments that identified the solid and fluid phases of a granular medium. The fluidity of the medium was determined by measuring the final depth of a cylinder dropped into it. We also developed a force model to describe the dynamics of the cylinder in the material, and compared the model to the experimental data. The final depth of the dropped cylinder was found to decay exponentially with increasing radius, its value becoming negligible at some value r_threshold. This value marks the transition from the fluid phase to the solid phase. A criterion was developed for identifying this threshold value, which was found to vary with the mass of the dropped cylinder.