Analysis of granular flow in aerated and vibrated chutes

Granular materials in flow exhibit behavior that is both solid-like and fluid-like. When subjected to slow deformation in a dense state, the stress within a granular medium is independent of the rate of deformation. In this regime, individual grains are in semi-permanent contact with their neighbors and stress is generated as a result of 'rubbing' between grains. In a very different regime, which occurs during rapid deformation and at moderate to low densities, the grains are in vigorous motion and momentum is transferred as a result of short-term collisions between grains. The stress in this situation has a quadratic dependence on the rate of deformation. These two regimes are extremes, though, and most practical situations fall somewhere in between. Recently, a constitutive theory has been proposed for general situations where both modes of momentum transport may be present. This 'frictional-collisional' constitutive theory has been used in this thesis to study granular flow in chutes, aided by the mechanisms of aeration and vibration.;In many situations of industrial import, the interaction of grains with the interstitial fluid plays an important role in determining the nature of the flow. This thesis attempts to incorporate the effect of the interstitial fluid on granular motion. The two phases are treated as interacting continua and the coupled equations of motion for both phases are given. This theory is then applied to the problem of granular flow in an inclined, aerated chute. The flow of the fluid (air) in this problem is perpendicular to the direction of flow of the granular medium. The governing equations for aerated chute flow are solved numerically for a range of flow parameters, such as the angle of inclination of the chute, the aeration velocity and the flow depth. In addition, experiments of aerated chute flow were conducted and measurements were made of the mass flow rate, mass holdup, flow depth and velocity profiles for a variety of conditions. The predictions of the theory are compared with experimental observations.;Aeration acts to relieve the stress in the granular medium and, as a result, increases the bulk flow velocity. The effect of vibration as a stress relieving mechanism is also explored in this work. A boundary condition that accounts for the production of fluctuational energy at a vibrating boundary is derived and applied to the problem of granular flow in a chute with a vibrating base. The governing equations for vibrated chute flow are again solved and the predictions of the theory are given. In addition, it is shown that the interplay of the frictional and collisional stresses leads to a variety of interesting behavior, including multiplicity of solutions, for chute flow in general.