Particulate Matter Flow And Static Number Of Issues

In the last few decades, granular matter has gradually become an active field in physics. As one of the most popular materials in this world, it does very important role in the industrial and agricultural processes and in the understanding of geological processes. In this thesis, using experimental method and computer simulation, we have studied several problems in granular flow and the static properties of granular material. They are the effect of boundary restriction on the granular flow, the bulk elasticity of granular assemble and the effect of horizontal vibration on the sandpile avalanche.In the first chapter, it is a brief review of history and current status of the granular matter, mainly included the static properties, the flowing properties, the properties under vibration and the corresponding background of applications.In Chapter 2, the effect of channel width on the granular flow in a funnel is studied. The experiment has found that the granular flow is easier to be transferred from dilute to dense if it is in a wider channel without any change to the other conditions, such as the initial incoming flux, the exit size of the funnel. Molecular simulation (MD) reveals that the transition of the flow from dilute to dense is decided by the distribution of the collision orientation near the funnel exit. The channel width is able to influence this distribution as same as the exit size and the incoming flux.In Chapter 3, the boundary effect on the rapid chute granular flow is studied. Our experiment has found that the boundary roughness, chute width and incline all can influence the transverse profile of the flux. A double-humped transverse profile is also found. We studied the evolution of the density and velocity profiles of chute flow by MD simulation and found the double-humped transverse profile is a precursor, which informs the flow to be farther diffused by the boundary stimulation.In Chapter 4, we studied the bulk elasticity of a granular assemble by MD simulations. Simulation results show that it does has an exponent larger than 3/2 in the elastic expression when the deformation is small, as Ppiston= k(δ/d)α, a=3.5, which well matches the used experimental results. When the deformation becomes large, the elastic behavior will return to be a Hertz form with a= 1.5, but the assemble becomes more hard because the increasing of the coefficient k. Simulation reveals that this behavior is caused by the structural rearrangement under the outside pressure, and can be identified by the distribution of vertical stress in assemble.Finally, in Chapter 5, the mechanics of sandpile avalanche has been studied using a horizontal vibration as an outside perturbation. Experiment result reveals that the avalanche is mainly decided by the magnitude of the outside force but not its form. The size effect can be negative if the sandpile is large enough. Under the vibration, the pile itself has an inside shock absorption, and this behavior can be described by a corrected Mohr-Coulomb criterion. On the other hand, the surface of the sandpile is not able to resist large extrusion stress, which can be an additional criterion to describe the mechanics of sandpile avalanche.