Andy Wilkins

• The Commonwealth Scientific and Industrial Research Organisation

In this study, we conduct a comprehensive history matching study for the FluidFlower benchmark model. This benchmark was prepared and organized by the University of Bergen, the University of Stuttgart, and Massachusetts Institute of Technology, for promoting understanding of the complex physics of geological carbon storage (GCS) through in-house ex...

The FluidFlower International Benchmark Study is a unique chance to assess the uncertainties introduced by numerical modelling through comparison to high-quality experimental data. A complete description of how the experiment was modelled by CSIRO is presented here, from the simplified model of the tracer tests and subsequent inversion of the perme...

The last 2 years have been a period of unprecedented growth for the MOOSE community and the software itself. The number of monthly visitors to the website has grown from just over 3,000 to now averaging 5,000. In addition, over 1,800 pull requests have been merged since the beginning of 2020, and the new discussions forum has averaged 600 unique vi...

This report presents the results of the research work performed under a Geoscience Australia – CSIRO collaboration to calculate diffuse rainfall recharge to the Great Artesian Basin groundwater system, with particular focus on the intake beds. The final result is shown in Figure 1. This data displayed in Figure 1, gridded to a 2.5km resolution, is...

Coal seam permeability is a critical factor in coal seam gas extraction and gas outburst control. In Australian coal mines, coal seam permeability is normally estimated using a packer test or drill stem test. In contrast, Chinese coal mines generally estimate a parameter called the “gas conductivity coefficient” by measuring natural gas flow rates...

Most of the published research on goaf-hole failures are performed using 2D numerical analyses. However, 2D analyses of the goaf-hole failure mechanism, which is truly a 3D problem, often do not provide a full picture of strata movement and stress change effect. In particular such 2D models completely fail to capture the longitudinal deformation an...

Chloride deposition-rate measurements at points within Australia are upscaled to the entire continent on a regular 0.05° grid. The upscaling uses a double-exponential correlation between deposition rate and distance to the coast, where the parameters in the double-exponential are spatially varying. These parameters are estimated using least-squares...

Aquifer Thermal Energy Storage (ATES) uses excess thermal energy to heat water which is stored in an aquifer until it is needed, at which time the hot water is recovered and the heat used for some purpose e.g. electricity generation. The recovery efficiency (i.e. the ratio of heat energy recovered to heat energy injected, R) is one of the most impo...

Realistic modelling of tightly coupled hydro-geomechanical processes is relevant for the assessment of many hydrological and geotechnical applications. Such processes occur in geologic formations and are influenced by natural heterogeneity. Current numerical libraries offer capabilities and physics couplings that have proven to be valuable in many...

The geomechanical response of a porous reservoir due to injection of fluid can result from a complex interplay between the changes in porepressure and temperature near the wellbore. As a result, predictions are usually made using either simplified analytical models, which may apply unrealistic assumptions in order to produce a tractable model, or d...

Numerical-simulation studies of transport and flow in porous media are essential in many practical fields of research. Including the coupling of different physical processes allows accurate modelling of the effects of fluid flow and temperature changes on the subsurface reservoir structure, and conversely, the effects of reservoir-structure changes...

Realistic modelling of tightly coupled hydro-geomechanical processes is relevant for the assessment of many hydrological and geotechnical applications. Such processes occur in geologic formations and are influenced by natural heterogeneity. Current numerical libraries offer capabilities and physics couplings that have proven to be valuable in many...

During underground longwall coal extraction, overburden strata deformation may result in vertical goaf drainage holes, which are drilled in advance of mining for tail gate gas management, to fail. The performance of these vertical goaf drainage holes is controlled by mine design parameters and local geomechanical properties. This paper investigates...

This paper presents an assessment of the hydrological impacts of proposed coal mines and coal seam gas (CSG) developments in the Gloucester, Hunter, Namoi and Galilee subregions of eastern Australia. Surface water and groundwater modelling was carried out to assess the cumulative regional-scale hydrological impacts of multiple coal and coal seam ga...

Microseismic monitoring in mining can potentially forecast catastrophic disasters, and help in the optimization of day-to-day operational and safety issues. However, it is difficult to fully utilize microseismic data due to the large quantity of small microseismic events and because automatically detecting events is frustrated by the pollution of t...

The Liu-Elsworth (1997) formalism that predicts permeability in deformed fractured rock has been highly useful and successful in numerous engineering situations involving mining, coal-bed methane and shale gas extraction. The formalism assumes the rock's fractures are aligned with three orthogonal axes and that the rock is subjected to strains alon...

Many models of plasticity are built using multiple, simple yield surfaces. Examples include geomechanical models and crystal plasticity. This leads to numerical difficulties, most particularly during the stress update procedure, because the combined yield surface is nondifferentiable, and when employing implicit time stepping to solve numerical mod...

Three new contributions to the field of multisurface plasticity are presented for general situations with an arbitrary number of nonlinear yield surfaces with hardening or softening. A method for handling linearly dependent flow directions is described. A residual that can be used in a line search is defined. An algorithm that has been implemented...

Synthetic rock mass modelling is based on estimating the mass scale properties of rock directly from properties of the intact material and observed jointing geometry and strength. This technique explicitly represents characteristics of the rock mass that are implicit in the widely applied, empirical Hoek-Brown strength criterion. We demonstrate her...

We demonstrate that care must be taken in a finite-element discretisation of multi-phase compressible Darcy flow, otherwise constraints of non-negativity of fluid mass can become violated. Generalising a technique pioneered by Dalen, a lumped, finite-difference-inspired approximation with upstream weighting is described. This is numerically cheap,...

The level-set method of topology optimization is used to design isotropic two-phase periodic multifunctional composites in three dimensions. One phase is stiff and insulating whereas the other is conductive and mechanically compliant. The optimization objective is to maximize a linear combination of the effective bulk modulus and conductivity of th...

The fracture resistance of structures is optimized using the level-set method. Fracture resistance is assumed to be related to the elastic energy released by a crack propagating in a normal direction from parts of the boundary that are in tension, and is calculated using the virtual crack extension technique. The shape derivative of the fracture-re...

Plastic yield criteria for porous ductile materials are explored numerically using the finite-element technique. The cases of spherical voids arranged in simple cubic, body-centred cubic and face-centred cubic arrays are investigated with void volume fractions ranging from 2 % through to the percolation limit (over 90 %). Arbitrary triaxial macrosc...

A one-dimensional computational model of pilling of a fibre assembly has been created. The model follows a set of individual fibres, as free ends and loops appear as fuzz and arc progressively withdrawn from the body of the assembly, and entangle to form pills, which eventually break off or are pulled out. The time dependence of the computation is...

Mechanistic models of pilling are discussed in general terms, and a framework for pilling simulations is thereby created. A fundamental flaw in earlier models of pilling is revealed. A more comprehensive model of fibre diffusion and withdrawal from the fabric is proposed, and this is solved in general terms to find the rate of fuzz growth. Fuzz wea...

Finite-element simulations are used to obtain many thousands of yield points for porous materials with arbitrary void-volume fractions with spherical voids arranged in simple cubic, body-centred cubic and face-centred cubic three-dimensional arrays. Multi-axial stress states are explored. We show that the data may be fitted by a yield function whic...

Previous studies of the mechanics of fiber assemblies have neglected fiber movements that are due to perturbations of the assembly. Axial movements, which are treated in the paper, are important in pilling, bagging, felting, and incremental drafting of yarns in weaving, but lateral movements may also occur. A dynamical model is analogous to molecul...

Eighteen cleaned and degreased Perendale wool fibres, which were as free as possible from external and internal stresses, were photographed, the images scanned to computer, and their space curves reconstructed. Various relations between the fibres' curvature and torsion were discovered which point to the possibility of a statistical description of...

Couplings between a closed string RR field and open strings are calculated in a system of coincident branes and antibranes of type II theory. The result can be written cleanly using the curvature of the superconnection.

We show how a theorem of Sullivan provides a precise mathematical statement of a 3D holographic principle, that is, the hyperbolic structure of a certain class of 3D manifolds is completely determined in terms of the corresponding Teichmüller space of the boundary. We explore the consequences of this theorem in the context of the Euclidean Bañados-...

We show how a theorem of Sullivan provides a precise mathematical statement of a 3d holographic principle, that is, the hyperbolic structure of a certain class of 3d manifolds is completely determined in terms of the corresponding Teichmuller space of the boundary. We explore the consequences of this theorem in the context of the Euclidean BTZ blac...

We compute the effective action for scattering of three well-separated extremal brane solutions, in 11d supergravity, with zero p− transfer and small transverse velocities. Using an interpretation of the conjecture of Maldacena, following Hyun, this can be viewed as the large N limit of the Matrix theory description of three supergraviton scatterin...

We compute the effective action for scattering of three well-separated extremal brane solutions, in 11d supergravity, with zero p_ transfer and small transverse velocities. Using an interpretation of the conjecture of Maldacena, following Hyun, this can be viewed as the large N limit of the Matrix theory description of three supergraviton scatterin...

The first massive level of closed bosonic string theory is studied. Free-field equations are derived by imposing Weyl invariance on the worldsheet. A two-parameter solution to the equation of motion and constraints is found in two dimensions with a flat linear-dilaton background. One-to-one tachyon scattering is studied in this background. The resu...

We examine the claim that the effective action of four-dimensional SU(2)_L gauge theory at high and low temperature contains a three-dimensional Chern-Simons term with coefficient being the chemical potential for baryon number. We perform calculations in a two-dimensional toy model and find that the existence of the term is rather subtle. Comment:...

Tegel Foods is New Zealand's leading producer and supplier of poultry prod-ucts, providing an extensive range of quality poultry products to New Zealanders for over thirty years. Tegel is a fully-integrated poultry producer involved in breed-ing, hatching, feeding, growing, processing and marketing of chicken and turkey in New Zealand. The problem...

Water-temperature control during the fill phase of a new kind of washing ma-chine being developed by Fisher and Paykel is considered. The machine and the fill method are described, and the factors which affect temperature control are explored. A steady-state mass and energy balance of the system, and a linearised analysis of the differential equati...