T. J. Donohue

The Prediction of Permeability with the Aid of Computer Simulations

The particular area of focus for this study is the use of theory to predict the permeability of a material through the use of the Ergun equation and the Kozeny-Carman equation along with computer simulations. The Ergun equation is well known for estimating permeability, and the Kozeny-Carman equation has also been used to a lesser extent. Existing literature extensively covers the use of these equations with homogeneous materials containing mono-size particles. In this study, an alternative way is sought to characterize mixtures that is based on the structure of the porosity, or void size, rather than the traditional method of using mean particle diameter. In doing so, this allows the Ergun and Kozeny-Carman equations to be rewritten to provide for an expansion in the type of mixtures that they can be applied to. Results are presented in this article on the application of these equations to mixtures including mono-size particles, then modified to include binary and distributed mixtures.

A New Approach for Calculating the Mass Flow Rate of Entrained Air in a Freefalling Material Stream

This article presents the outcomes from a series of physical experiments to measure the air entrainment rates encountered within a stream of freefalling particles. The experimental work presented spans a range of particle parameters and hopper geometries. From these results a new theory for the prediction of air entrainment is developed and presented. This new method was developed specifically to facilitate a better understanding in the area of fugitive dust control associated with material handling systems, which are driven by the air entrainment during freefalling. From the work presented in this article, a better prediction capability of freefalling bulk materials in either constrained, or unconstrained systems, will allow for the optimization of either passive or active dust control strategies. This article presents several distinct sections that detail the experimental work used to determine the freefall stream parameters that were conducted to allow the development of the entrainment equations.

Application of the image processing technique in identifying the particle dispersion from a centrifugal fertilizer spreader

ABSTRACT Particle dispersion in the vicinity of an agricultural fertilizer spreader is difficult to capture due to the rapid particle traveling motion. This paper introduced a granule impact indentation-based technique to simultaneously record the two-dimensional particle dispersion from a spinning concave disc type of spreader. A Nitrogen-Phosphorus-Potassium (NPK) type of fertilizer was utilized to induce indentations on aluminum foils placed on the wall panels confining an experimental spreader system. Subsequently, an image processing technique which is comprised of the multicolor edge detection, the curve closing, and the region merging techniques was purposely developed to automatically identify and locate the granule impacts on the sampled foil digital images. Overlapping impacts were characterized based on the granulometry of the fertilizer sample. The reconstructed particle dispersion pattern using the image processing method showed good agreement with the experimental observations. The outcome of this research enabled a fast and effective method for quantitatively assessing the particle distribution for a specific fertilizer spreader.

Application of the Coupled Discrete Element Modelling and Modelica Based Multi-body Dynamics in System-Level Modelling

Discrete element modelling (DEM) has been widely used in many industries to investigate the particulate interactions during the storage, handling and transport. However, in many cases, it is the interaction between the particulate assembly and the associate mechanical/electrical/hydraulic components determining the system performance, in which case DEM alone is not able to model. The research presented in this paper developed a framework for coupling DEM with multibody dynamics (MBD) to model not only inter-granular particle interactions, but also the influence of the particle contacts on other associated system components. The coupling principle and realization methods were initially discussed. A case study on sand mixing using a pneumatic motor was then performed to test the developed methodology. Results indicated that the coupled DEM-MBD framework is able to reflect system level dynamics more realistically than DEM alone.

On the Use of the Uniaxial Shear Test for DEM Calibration

Discrete Element Modelling (DEM) is a widely used and useful tool in the materials handling field. It is commonly used in the design of transfer chutes, bins, hoppers and feeders. However, there is still uncertainty in the translation of material characteristics that are measured experimentally in the laboratory to DEM parameters. There is a vast array of literature on this topic, with most of this work focusing on physical tests in the laboratory such as the angle of repose test, shear tests, compression tests and sliding friction tests. This paper investigates the use of a uniaxial shear test, conducted on a large scale with gravity switched off, for the development of flow functions to allow ease of comparison to experimental tests. A linear cohesion contact model was used in the simulations presented in this study.

DEM Modelling of Silo Loads Asymmetry Induced by Eccentric Discharge

The eccentric discharge of bulk solids from a silo can lead to asymmetry in the normal pressure distribution around the silo walls. In this study, the wall loads of square silos during the eccentric discharge operation were investigated by performing a range of DEM simulations. The DEM results indicate that the wall pressure on the side furthest from the eccentric discharge location was larger than that on the nearest side, being comparable to those derived from AS3774. The DEM results also show significant variation in the wall load distributions around the silo walls. The DEM simulations are also used to explore the effects of a number of parameters, i.e. particle-particle friction coefficient, rolling friction coefficient and outlet eccentricity.

Investigation of belt conveyor transfer chute configurations to reduce dust generation using CFD modeling

“Passive” dust control systems for belt conveyor transfer stations have become increasingly popular in recent years. Effective design relies on a fundamental understanding of the flow of granular material and air throughout the transfer chute. This paper presents an investigation into the flow properties of the air and particles in the enclosure for different transfer chutes based on computational fluid dynamics (CFD) modelling. A multiphase Euler-Euler model was applied to develop a 3D model of the transfer chute. Experiments were undertaken to verify the theoretical models, with overall results indicating good correlation. Furthermore, a number of alternative transfer chute configurations were modelled to investigate the effect of geometry on dust generation.