Dr. Gary W. Delaney

Digital Productivity Flagship,
CSIRO Melbourne, Australia

Research Interests

I lead the Industrial Systems Modelling Team at the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Melbourne. My primary research interests are in computational modelling and structural characterization of granular systems, and applications of Machine Learning in understanding and optimizing natural and industrial processes.


The packing properties of superellipsoids

We investigate the properties of packings of frictionless non-spherical particles utilizing a dynamic particle expansion technique. We employ superquadric particles (superellipsoids), which allows us to explore how a broad range of particle shapes affect both the macroscopic and the local configurational properties of the system. We smoothly transition from spherical particles possessing only translational degrees of freedom to large aspect ratio non-spherical grains where rotational degrees of freedom are highly important. We demonstrate that the degree of anisotropy and local surface curvature of the particles have a profound effect on their packing properties, determining whether a random or an ordered packing is readily formed. Details of this work is given in our paper The packing properties of superellipsoids .

Rotational Random Apollonian Packing (RRAP)

Scientists have long considered packing models in which non-overlapping grains of smaller and smaller sizes are placed according to a specified set of rules. These date back to the work of Apollonius of Perga ca. 200B.C. We have performed extensive numerical simulations using up to 106 grains for a range of polygonal and elliptical shapes using both the traditional Random Apollonian Packing (RAP) model and also a new model which takes into account the extra rotational degree of freedom of non-circular grains. We term this model Rotational Random Apollonian Packing (RRAP). Grains packed in the RRAP model are observed to generate denser packings. We explain the dependence of the packing efficiency on the grain shape via the identification of the key constraining lengths that limit the growth of the grains during the packing process. Full details of this work is given in our paper Relation Between Grain Shape and Fractal Properties in Random Apollonian Packing with Grain Rotation.

Random Packing of Ellipses

I have written a software package that employs a Monte-Carlo type packing algorithm to generate dense jammed random packings of 2D grains of arbitrary shape. We have used this to investigate the packing properties of elliptical grains, with a very interesting variation in the packing density of the grains observed as the ellipticity is varied. A video of the generation of a packing of ellipses with an aspect ratio of 0.7 can be downloaded here ( Mpeg 23.6MB). Full details of this work is given in our paper Random packing of elliptical disks.

Newton's Cradle - A 1D Granular System

In textbook descriptions of Newton's cradle, it is generally claimed that displacing one ball will result in a collision that leads to another ball being ejected from the line, with all others remaining motionless. It has however been shown that a realistic description is more subtle. We have performed simulations of Newton's cradle that reproduce the initial break-up of the line of balls at the first collision, the eventual movement of all the balls in phase, and is in good agreement with our experimentally obtained data. The first effect is due to the finite elastic response of the balls, and the second is a result of viscoelastic dissipation in the impacts. We have also analyzed a dissipation-free ideal Newton's cradle which displays complex dynamics. A video of our simulation can be downloaded here ( Mpeg 1.46MB). Full details of this work is given in our paper Rocking Newton's Cradle.

Onset of Rigidity for Stretched String Networks

We have defined and analysed an elementary model which has a close affinity to existing models that represent the compression of randomly packed soft spheres. That work is mainly founded on Hooke's Law type interactions which act under compression only. We have in effect turned this problem "inside-out", by defining Hooke's Law interactions under extension only, and hence a model of elastic strings that are loose under compression. Our simulations consist of a network of strings with random natural lengths. As this system is expanded, a threshold is reached where some of the strings form a taut string network. An animation of the expansion of a triangular network, with the loose strings colored black and the taut colored red, can be downloaded here ( Gif 5.9MB). Full details of this work is given in our paper Onset of rigidity for stretched string networks.

Selected Publications

1. "Onset of rigidity in 3D stretched string networks", G. W. Delaney and D. Khoury European Physical Journal B, 86, 44, 2013.

2. "Comparison of permeability of model porous media between SPH and LB", P.M. Dupuy, P. Austin, G.W. Delaney and M.P. Schwarz, Computer Physics Communications, 182, 2249-2258, 2012.

3. "Defining Random Loose Packing for Nonspherical Grains", G.W. Delaney, J.E. Hilton and P.W. Cleary, Physical Review E, 83, 051305, 2011.

4. "The packing properties of superellipsoids", G.W. Delaney and P.W. Cleary, Europhysics Letters , 89, 34002, 2010.

5. "Combining tomographic imaging and DEM simulations to investigate the structure of experimental sphere packings", G.W. Delaney, T. Di Matteo and Tomaso Aste, Soft Matter, 6, 2992-3006, 2010.

6. "Disordered spherical bead packs are anisotropic", G. E. Schroeder-Turk, W. Mickel, M. Schroeter, G. W. Delaney, M. Saadatfar, T. J. Senden, K. Mecke and T. Aste, Europhysics Letters , 90, 34001, 2010.

7. "Relation Between Grain Shape and Fractal Properties in Random Apollonian Packing with Grain Rotation", G.W. Delaney, S. Hutzler and T. Aste, Physical Review Letters, 101, 120602, 2008.

8. "Crystalline arrangements of microbubbles in monodisperse foams", A. van der Net, G.W. Delaney, W. Drenckhan, D. Weaire and S. Hutzler, Colloids And Surfaces A-Physicochemical And Engineering Aspects , 309 , 117-124, 2007.

9. "Onset of rigidity for stretched string networks", G.W. Delaney, D. Weaire and S. Hutzler, Europhysics Letters , 72 , 990-996, 2005.

10. "Rheology of ordered foams on the way to Discrete Microfluidics", W. Drenckhan, S.J. Cox, G. Delaney, H. Holste, D. Weaire and N. Kern, Colloids And Surfaces A-Physicochemical And Engineering Aspects , 263 52-64, 2005.

11. "Random packing of elliptical disks", G. Delaney, D. Weaire, S. Hutzler and S. Murphy, Philosophical Magazine Letters , 85 2005, 89-96, 2005.

12. " Rocking Newton's Cradle ", S. Hutzler, G. Delaney, D. Weaire and F. MacLeod, American Journal Of Physics , 72 2004, 1508-1516, 2004.

Email: gdelaney "AT" gmail "DOT" com