Thesis (PhD (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2004. / Granular flow occurs in a broad spectrum of industrial applications that
range from separation and mixing in the pharmaceutical industry, to grinding
and crushing, blasting, stockpile construction, flow in and from hoppers,
silos, bins, and conveyer belts, agriculture, mining and earthmoving.
Two totally different approaches of modelling granular flow are the Discrete
Element Method (DEM) and continuum methods such as Finite Element
Methods (FEM). Continuum methods can be divided into nonpolar or
classic continuum methods and polar continuum methods. Large displacements
are usually present during granular flow which, without remeshing,
cannot be solved with standard finite element methods due to severe mesh
distortion. The Particle-in-Cell (PIC) method, which is a so-called meshless
method, eliminates this problem since all the state variables are traced by
material points moving through a fixed mesh.
The main goal of this research was to model the flow of noncohesive
granular material in front of flat bulldozer blades and into excavator buckets
using a continuum method. A PIC code was developed to model these processes
under plane strain conditions. A contact model was used to model
Coulomb friction between the material and the bucket/blade. Analytical
solutions, published numerical and experimental results were used to validate
the contact model and to demonstrate the code’s ability to model large
displacements and deformations.
The ability of both DEM and PIC to predict the forces acting on the blade
and bucket and the material flow patterns were demonstrated. Shear bands
that develop during the flow of material were investigated. As part of the
PIC analyses, a comparison between classic continuum and polar continuum
(Cosserat) results were made. This includes mesh size and orientation
dependency, flow patterns and the forces acting on the blade and the
bucket.
It is concluded that the interaction of buckets and blades with granular
materials can successfully be modelled with PIC. In the cases conducted
here, the nonpolar continuum was more accurate than the polar continuum,
but the polar continuum results were less dependent on the mesh
size. The next step would be to apply this technology to solve industrial
problems.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/1334 |
| Date | 03 1900 |
| Creators | Coetzee, Corne J. |
| Contributors | Basson, A. H., Vermeer, P. A., University of Stellenbosch. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | University of Stellenbosch |
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