Stresses on Rapidly Sheared Fluid-Solid Mixtures

Constitutive equations were derived describing the stress in a rapidly sheared mixture of granular cohesionless solids and a Newtonian fluid. These equations are considered to describe the flow of mixtures such as coal and oil in a pipeline or sediment suspended in a river. The stress is found to depend upon the following properties of the solid: diameter and density of the granular material, coefficient of kinetic friction, coefficient of restitution, and volumetric concentration. The density and viscosity of the interstitial fluid was also found to affect the stress within the granular mixture. The theoretically predicted shear stresses were found to be in good agreement with measured stresses determined from experimental studies where rapid shear flows were produced in mixtures formed from polystyrene spheres in air, polystyrene spheres in water, glass spheres in air and polystyrene spheres in air.