Many mining operations use large quantities of water to separate valuable minerals from less valuable gangue. This
dependence on liquid separation has an environmental impact in terms of energy and water use and also implies a cap on
production due to the availability of water. To address these problems, the CSIRO has developed the CSIRO Rotational
Classifier, which - by using the phenomena of rotational segregation - can quickly separate dry granular material in
terms of size and/or density without the use of any liquids.
The purpose of this paper is to obtain a deeper understanding of how rotational segregation can separate particles of
different densities in a rotating cylinder, free from any interstitial fluids. This was accomplished by analyzing a cross
section at the 20% fill level in a 50% full classifier, which contained a 50-50 ratio of glass and lead beads. The granular
bed was sampled at different time intervals over a 60 second period with a classifier rotation rate of 2 rpm. These
experiments resulted in a high segregation level of 0.9 in 20 seconds and 0.95 by 60 seconds (where a level of 1 implies
full segregation). The results then underwent image analysis and were subsequently compared to results from a discrete
element method (DEM) model where similar segregation ratios, albeit at longer timescales, were obtained. This study
gave a further insight into the segregation process particularly in terms of axial formation of the segregated core which
may one day be used in the separation of minerals.
Scalar transport in closed potential flows is investigated for the specific case of a periodically reoriented dipole
flow. For scalar advection, Lagrangian chaos can be achieved with breakdown of the regular Hamiltonian structure,
which is governed by symmetry conditions imposed by the dipole flow. Instability envelopes associated
with period-doubling bifurcations of fixed points govern which regions of the flow control parameter space admits
global chaos. These are further refined via calculation of Lyapunov exponents. These results suggest
significant scalar transport enhancement is possible within potential flows, given appropriate programming of
stirring protocols.
Complex interactions between advection and diffusion give rise to enhanced scalar transport in cases where the
advective field generates Lagrangian chaos. As the dispersion rate is a complex function of scalar diffusivity and
parameters controlling the flow field, resolution of scalar dispersion over this parameter space is useful for better
understanding interactions between advection and diffusion. In this paper we resolve the fine-scale structure
asymptotic transport over the flow parameter space for Peclet numbers from 100 to 105 for a physically realizable
flow, yielding a 50-fold acceleration of scalar dispersion at Pe = 105. These results generate considerable insight
into the global structure of transport and facilitate identification of mechanisms governing scalar dispersion;
features include fractal distributions of dispersion rate, solution mode-locking, an order-disorder transition and
localisation of transport optima.
In nature dissipative fluxes of fluid, heat, and/or reacting species couple to each other and may also couple
to deformation of a surrounding porous matrix. We use the well-known analogy of Hele-Shaw flow to Darcy
flow to make a model porous medium with porosity proportional to local cell height. Time- and space-varying
fluid injection from multiple source/sink wells lets us create many different kinds of chaotic flow and chemical
concentration patterns. Results of an initial time-dependent potential flow model illustrate that this is a partially
open flow, in which parts of the flow remain in the cell forever and parts pass through with residence time and
exit time distributions that have self-similar features in the control parameter space of the stirring.
Proceedings Volume Editor (1)
This will count as one of your downloads.
You will have access to both the presentation and article (if available).
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.