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Forced granular flowCoetzee, C. J. (Cornelis Jacobus) 12 1900 (has links)
Thesis (MEng)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: The main goal of the thesis is to validate the ability of discrete element methods (DEM)
to predict forced granular flow. Granular flow occurs in a broad spectrum of industrial
applications. The thesis focuses on earthmoving processes typical of the mining and
agricultural industries. Existing soil mechanics soil-tool models are also investigated
and general flow behaviour in and around blades and buckets are established.
Soil mechanics theories are used to predict the draft forces on a flat blade moving
through granular material. Com and wheat grains are used as material. The rupture
(slip) lines in front of the blade are predicted by soil mechanics and compared to
experimental results. A two-dimensional test bench is used to visualise the flow of the
granular material. Forces and moments that act on the tools are measured.
DEM can be used to model industrial granular flow with large displacements. Two
types of earthmoving equipment are simulated. The first is a flat blade and the second is
a bucket. The forces on these tools are determined using DEM and compared to
experimental results. The ability of DEM to predict material compressibility, the flow
of material in and around the tools, the rupture lines and the bucket fill rate are
investigated. A particle relative displacement method is used to determine the rupture
lines. / AFRIKAANSE OPSOMMING: Die hoofdoel van die tesis is om die vermoë van diskrete-element-metodes (DEM) om
geforseerde partikelvloei te voorspel, te ondersoek. Partikelvloei word aangetref in 'n
breë spektrum van industriële toepassings. Die tesis fokus op grondverskuiwing soos
aangetref in myn- en landbouprosesse. Bestaande grondmeganika-modelle word ook
ondersoek, asook die algemene gedrag van partikelvloei in en rondom lemme en bakke.
Die grondmeganika-modelle word hoofsaaklik gebruik om die kragte op lemme te
voorspel. Glip (skuif)-vlakke word ondersoek en vergelyk met eksperimentele resultate.
'n Twee-dimensionele toetsbank word gebruik om die vloei waar te neem. Die kragte
en momente op die toerusting word ook gemeet. Mielie- en koringpitte word as
materiaal gebruik.
DEM kan gebruik word om industriële partikelvloei met groot verplasings te modelleer.
Twee tipes toerusting word gesimuleer. Die eerste is 'n plat lem en die tweede 'n bak.
Die kragte en momente op dié toerusting word bepaal m.b.V. DEM en dan vergelyk met
die eksperimentele resultate. Die vermoë van DEM om materiaalsamedrukking,
vloeipatrone, glipvlakke en bakvul-tempo's te voorspel word ondersoek. 'n Partikelrelatiewe-
verplasings-metode word gebruik om die glipvlakke te voorspel.
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An experimental and numerical study of granular hopper flowsSandlin, Matthew 13 January 2014 (has links)
In a proposed design for a concentrated solar power tower, sand is irradiated by
solar energy and transfers its energy to another fluid stream by means of a finned tube
heat exchanger. To maximize heat transfer and minimize potential damage to the heat
exchanger, it is desired to have a very uniform flow through the heat exchanger.
However, performing full scale flow tests can be expensive, impractical, and depending
upon the specific quantities of interest, unsuitable for revealing the details of what it
happening inside of the flow stream.
Thus, the discrete element method has been used to simulate and study particulate
flows. In this project, the flow of small glass beads through a square pyramid shaped
hopper and a wedge shaped hopper were studied at the lab scale. These flows were also
simulated using computers running two versions of discrete element modeling software –
EDEM and LIGGGHTS. The simulated results were compared against the lab scale flows
and against each other. They show that, in general, the discrete element method can be
used to simulate lab scale particulate flows as long as certain material properties are well
known, especially the friction properties of the material. The potential for increasing the
accuracy of the simulations, such as using better material property data, non-uniform
particle size distributions, and non-spherical particle shapes, as well as simulating heat
transfer within a granular flow are also discussed.
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