Convective and segregative mechanisms in vibrofluidised granular systems

Granular materials display a host of fascinating behaviours both remarkably similar to and strikingly different from those exhibited by classical solids, liquids and gases. Due to the ubiquity of granular materials, and their far-reaching importance in multitudinous natural and industrial processes, an understanding of their dynamics is of the utmost importance to modern society. In this thesis, we analyse in detail two phenomena, one from each of the above categories: granular convection, a behaviour directly analogous to the Rayleigh-Benard cells observable in classical fluids, and granular segregation, a phenomenon without parallel in classical, molecular physics, yet which is known to greatly impact various physical and industrial systems. Through this analysis, conducted using a combination of the experimental positron emission particle tracking technique and discrete particle method simulations, we aim to improve our knowledge of these processes on a fundamental level, gaining insight into the factors which may influence them, and hence how they may be effectively controlled, augmented or eliminated

Effect of cylinder wall parameters on the final packing density of mono-disperse spheres subject to three-dimensional vibrations

Achieving densely packed particles is desirable within the industries of ceramics, pharmaceuticals, defence and additive manufacturing. In this work, we use the discrete element method (DEM) to determine the effect of wall parameters on the final packing density of mono-disperse spheres subject to 4 varying three-dimensional vibration and fill conditions. We focus specifically on the impact of the container wall parameters on the particles' final packing density. Following on from the validation of the DEM simulation the particle-wall coefficient of restitution, the particle-wall coefficient of rolling friction and the particle-wall coefficient of sliding friction were varied individually and the effect on the final packing density analysed. For relatively low particle-particle friction glass beads, the effect of these wall properties had no discernible effect on the final packing density achieved. Following on from these findings the particle-wall properties were varied at the extreme values of particle-particle coefficient of rolling friction and particle-particle coefficient of sliding friction. For a particle-particle coefficient of sliding friction = 1, increases in particle-wall coefficient of restitution resulted in a minor increase in the final packing density of particles though this was not statistically significant. For a particle-particle coefficient of sliding friction = 1, increases in particle-wall coefficient of rolling friction resulted in a minor decrease in the final packing density of the particles though again not to a degree where the trend can, with complete certainty, be distinguished from the random error across the repeats. Finally, when the particle-particle coefficient of sliding friction = 1, increases in particle-wall coefficient of sliding friction resulted in a significant decrease in the final packing density of particles. This decrease was attributed to the propagation of force chains throughout the packing. The significant decrease in final packing density with particle-wall coefficient of sliding friction highlights the need to choose appropriate vessel materials to optimise packing of particles with a high particle-particle coefficient sliding friction. Conversely, for particles with minimal particle-particle friction, the particle-wall friction coefficient has no effect on the final packing density of particles - a potentially valuable finding for certain industrial applications. All simulations were run using the open-source DEM package LIGGGHTS on the University of Birmingham's high-performance computer: BlueBEAR. All the code files used within this paper can be found on Github: https://github.com/Jack-Grogan/DEM-Vibropacking-Wall-Effects

Mercury DPM: fast, flexible particle simulations in complex geometries part II: applications

MercuryDPM is a particle-simulation software developed open-source by a global network of researchers. It was designed ​ab initio to simulate realistic geometries and materials, thus it contains several unique features not found in any other particle simulation software. These features have been discussed in a companion paper published in the DEM7 conference proceedings; here we present several challenging setups implemented in MercuryDPM ​ . Via these setups, we demonstrate the unique capability of the code to simulate and analyse highly complex geotechnical and industrial applications.These tups implemented include complex geometries such as (i) a screw conveyor, (ii) steady-state inflow conditions for chute flows, (iii) a confined conveyor belt to simulate a steady-state breaking wave, and(iii)aquasi-2D cylindrical slice to efficiently study shear flows.​MercuryDPM is also parallel, which we showcase via a multi-million particle simulations of a rotating drum. We further demonstrate how to simulate complex particle interactions, including: (i)deformable, charged clay particles; and (ii) liquid bridges and liquid migration in wet particulates, (iii) non-spherical particles implemented via superquadrics. Finally, we show how to analyse and complex systems using the unique micro-macro mapping (coarse-graining) tool MercuryCG

Comparative return of imports into the state of Negri Sembilan during the years, 1916 and 1915.

Supplement to the F.M.S Government Gazette, May 11th, 1917. It also contains 'Comparative return of exports into the state of Negri Sembilan during the years, 1916 and 1915'

MercuryDPM: Fast, flexible particle simulations in complex geometries: Part B: Applications

MercuryDPM is a particle-simulation software developed open-source by a global network of researchers. It was designed ​ab initio to simulate realistic geometries and materials, thus it contains several unique features not found in any other particle simulation software. These features have been discussed in a companion paper published in the DEM7 conference proceedings; here we present several challenging setups implemented in MercuryDPM​. Via these setups, we demonstrate the unique capability of the code to simulate and analyse highly complex geotechnical and industrial applications. The setups implemented include complex geometries such as (i) a screw conveyor, (ii) steady-state inflow conditions for chute flows, (iii) a confined conveyor belt to simulate a steady-state breaking wave, and (iii) a quasi-2D cylindrical slice to efficiently study shear flows. ​MercuryDPM is also parallel, which we showcase via a multi-million particle simulations of a rotating drum. We further demonstrate how to simulate complex particle interactions, including: (i) deformable, charged clay particles; and (ii) liquid bridges and liquid migration in wet particulates, (iii) non-spherical particles implemented via superquadrics. Finally, we show how to analyse and complex systems using the unique micro-macro mapping (coarse-graining) tool MercuryCG