The Study Of Particle Dynamics And Size Segregation In A Cylinder Sheared Granular Materials

Many particle flow phenomenon,such as landslide,debris flow,food processing and drug production,widely exist in nature and industrial manufacture.The behavior of particle materials exhibit different phases such as solid-liquid phases under different conditions.But even in the fluid state,its behavior is obviously different from the fluid.In order to study the particle flow characteristics,a continuous particle flow model should be established.The cylinder couette flow is that particles are confined in a coaxial cylinder flow by inner and outer cylinder rotation.As the inner cylinder diameter is relatively small,the particle flow region becomes narrower.For the investigation of flow characteristics and the size separation in a wider range,the experiment adopts the device in which outer cylinder rotate and inner cylinder is fixed.The main works of this paper are as follows:1.Using high-speed camera technology investigate the particle circular motion,radial motion and shear band in terms of the rotating speed,initial height of particles and influence of bottom boundary roughness.The results show that radial separation movement of particles occurs on the free surface.A critical ring appears in the radial direction of shear band.With the increasing of rotating speed,the critical ring toward to the outer cylinder.With the initial height of particles,the critical ring toward to the inter cylinder continually.The roughness of bottom boundary inhibit the particles motion.The roughness of bottom boundary reduce rotating speed and narrow the shear band.At the same time,the critical ring toward to the outer cylinder.2.Using high-speed camera technology trace the spherical shell rising in the particles flow to investigate the size separation.The spherical shell's rising time and angular displacement is studied from outer cylinder rotating speed,the sizes,initial radial displacement and weight of spherical shell,and initial height of particles.The results show that with the increasing of rotating speed and the particle flow-velocity the rising time of spherical shell is shortened,and the angular displacement increases.With the increasing of diameter of spherical shell and"buoyancy",the rising time of spherical shell is shortened,and the angular displacement decreases.With the increasing of radial displacement between spherical shell and outer cylinder,the particle flow-velocity slow.As the angular velocity fast decaying along the outer cylinder,rising time of spherical shell is shortened,and the angular displacement decreases.With the increasing of initial height of particles and the weight of spherical shell,the longer rising time of spherical shell make the angular displacement increases.