Flow characteristics and stresses on cylindrical objects immersed in a flow of inelastic hard disks

Granular flows have some applications in industry and nature which can be described and modeled similarly. Debris flow, snow avalanches and landslide are examples of natural events along with silos, hoppers and fluidized beds as industrial cases where flows of grains usually encounter with solid objects. In this paper, cylindrical objects of different radii with controllable surface roughness are exposed to a stream of inelastic hard disks in the absence or presence of gravity. A granular shock wave is developed around the solid object whose features are dependent of different geometric and physical parameters. In simulations, the event-driven algorithm has been used with binary inelastic collisions. The surface of cylindrical object is either smooth or covered by hard disks as the same ones in the main stream. Stresses due to successive collisions are calculated in normal and tangential directions at the surface of cylindrical object. Voronoi tessellation is performed to visualize the packing density in particle level. Results revealed that the coefficient of restitution has considerable effect on the features of granular shock wave where gravity displayed mild influence. However, the presence of gravitational acceleration raises the stress with a quadratic function though the ratio of stress and the flow pattern reaches to steady state fairly quickly. The surface roughness in the same order as the flow particles size yields a double amount for stresses in comparison to a perfectly smooth surface. The smaller object size was also found to tolerate larger force fluctuations with a weaker quality of flow branching. For local stresses, the peak value of fluctuations can reach 5 times greater than its mean.

A stream of granular matter hits a solid object yielding granular shock wave in front of object. The stream is either divided into two branches, or scattered. The stresses and corresponding fluctuations on the object are considered. They have various applications in landslide, debris flow, avalanches, silos, hoppers and fluidized beds. Particle dynamics simulations are used to study such flows.Figure optionsDownload as PowerPoint slideHighlights
► Packing of monodisperse disks in a rectangular region using hard disk model.
► Stresses and fluctuations with Voronoi tessellation are calculated.
► Effects of restitution coefficient, gravity, surface roughness and object size.
► Coefficient of restitution affects considerably on the granular shock wave anatomy.
► Surface roughness and object size notably affect on stress and stress fluctuations.