http://espace.library.uq.edu.au/ The University of Queensland en Fez http://blogs.law.harvard.edu/tech/rss http://espace.library.uq.edu.au/view/UQ:287738 This paper describes a new boundary focused mesh generation algorithm. The algorithm produces quadrilateral meshes from images of multi-material structures. The challenge of meshing such images is to create high quality elements which are aligned with complex material boundaries. The approach proposed in this paper uses the following steps: (1) extract boundaries according to pixel colours; (2) smooth the jagged boundaries; (3) generate geodesic isolines aligned with smoothed boundaries; (4) generate a mesh from the boundaries and isolines; (5) optimize the mesh using the " Pisces" pattern (which is introduced in this paper). Application examples are presented to contrast the reliability and effectiveness of the new algorithm with existing approaches. 2012-12-23T00:28:17Z Liu, Yan og Xing, H. L. http://espace.library.uq.edu.au/view/UQ:142330 2008-06-10T00:00:00Z Huang, L. og Mora, P. R. og Fehler, M. http://espace.library.uq.edu.au/view/UQ:150855 2008-06-06T00:00:00Z Mora, P. R. og Place, D. G. http://espace.library.uq.edu.au/view/UQ:67270 2007-08-15T00:00:00Z Weatherley, D. K. og Mora, P. R. http://espace.library.uq.edu.au/view/UQ:74392 A statistical fractal automaton model is described which displays two modes of dynamical behaviour. The first mode, termed recurrent criticality, is characterised by quasi-periodic, characteristic events that are preceded by accelerating precursory activity. The second mode is more reminiscent of SOC automata in which large events are not preceded by an acceleration in activity. Extending upon previous studies of statistical fractal automata, a redistribution law is introduced which incorporates two model parameters: a dissipation factor and a stress transfer ratio. Results from a parameter space investigation indicate that a straight line through parameter space marks a transition from recurrent criticality to unpredictable dynamics. Recurrent criticality only occurs for models within one corner of the parameter space. The location of the transition displays a simple dependence upon the fractal correlation dimension of the cell strength distribution. Analysis of stress field evolution indicates that recurrent criticality occurs in models with significant long-range stress correlations. A constant rate of activity is associated with a decorrelated stress field. 2007-08-15T00:00:00Z Weatherley, D og Mora, P http://espace.library.uq.edu.au/view/UQ:142328 2008-06-10T00:00:00Z Jaume, S. C. og Weatherley, D. K. og Mora, P. R. http://espace.library.uq.edu.au/view/UQ:37046 The evolution of event time and size statistics in two heterogeneous cellular automaton models of earthquake behavior are studied and compared to the evolution of these quantities during observed periods of accelerating seismic energy release Drier to large earthquakes. The two automata have different nearest neighbor laws, one of which produces self-organized critical (SOC) behavior (PSD model) and the other which produces quasi-periodic large events (crack model). In the PSD model periods of accelerating energy release before large events are rare. In the crack model, many large events are preceded by periods of accelerating energy release. When compared to randomized event catalogs, accelerating energy release before large events occurs more often than random in the crack model but less often than random in the PSD model; it is easier to tell the crack and PSD model results apart from each other than to tell either model apart from a random catalog. The evolution of event sizes during the accelerating energy release sequences in all models is compared to that of observed sequences. The accelerating energy release sequences in the crack model consist of an increase in the rate of events of all sizes, consistent with observations from a small number of natural cases, however inconsistent with a larger number of cases in which there is an increase in the rate of only moderate-sized events. On average, no increase in the rate of events of any size is seen before large events in the PSD model. 2007-08-13T00:00:00Z Jaume, SC og Weatherley, D og Mora, P http://espace.library.uq.edu.au/view/UQ:61053 2007-08-14T00:00:00Z Jaume, S. C. og Weatherley, D. K. og Mora, P. R. http://espace.library.uq.edu.au/view/UQ:150845 2008-06-06T00:00:00Z Jaume, S. C. og Mora, P. R. og Bufe, C. G. http://espace.library.uq.edu.au/view/UQ:150877 2008-06-06T00:00:00Z Winter, M. http://espace.library.uq.edu.au/view/UQ:149059 2008-06-06T00:00:00Z Weatherley, D. K. og Mora, P. R. http://espace.library.uq.edu.au/view/UQ:75785 The new Australian Computational Earth Systems Simulator research facility provides a virtual laboratory for studying the solid earth and its complex system behavior. The facility's capabilities complement those developed by overseas groups, thereby creating the infrastructure for an international computational solid earth research virtual observatory. 2007-08-15T00:00:00Z Mora, P og Muhlhaus, H og Gross, L og Xing, H og Weatherley, D og Abe, S og Latham, S og Moresi, L http://espace.library.uq.edu.au/view/UQ:255508 We examine the confined elastic buckling of a single N-particle force chain. For a given set of material parameters, a characteristic load-carrying capacity is attained for a clearly defined range of force chain lengths N ≥ L*. The rotation and translation of particles along periodically located segments of the critical buckling mode, each of length L*, are on average consistent with those for particles inside the shear band. Preliminary results from postbuckling analysis show that the critical buckling mode is unstable and that buckling culminates in a localized response over one of these segments where observed shear band kinematics prevail. Thus, the localized buckling response is characterized by the rotation of a finite number of particles with a clearly defined length L*. For a wide range of material properties, L* is around eight particle diameters - the observed shear band thickness for many granular materials, most notably sand. 2011-10-13T00:00:00Z Tordesillas, Antoinette og Hunt, Giles og Shi, Jingyu http://espace.library.uq.edu.au/view/UQ:204568 Earth scientists are probing the predictability issue of earthquakes from basically two directions: one group of researchers uses the statistical physics based methods such as LURR (Load-Unload Response Ratio), AMR (Accelerate seismic Moment Release) and Pattern Informatics. They ignore the details inside the crust but instead only observe the change of the crust as a whole. By comparing the changing pattern of a target block of crust with the pattern in other areas where the history of the pattern are known, they can deduce the state of the crust and make temporal prediction of the stability of that crust. 2010-04-30T00:00:00Z Xing, H. L. og Yin, C. http://espace.library.uq.edu.au/view/UQ:35696 To translate and transfer solution data between two totally different meshes (i.e. mesh 1 and mesh 2), a consistent point-searching algorithm for solution interpolation in unstructured meshes consisting of 4-node bilinear quadrilateral elements is presented in this paper. The proposed algorithm has the following significant advantages: (1) The use of a point-searching strategy allows a point in one mesh to be accurately related to an element (containing this point) in another mesh. Thus, to translate/transfer the solution of any particular point from mesh 2 td mesh 1, only one element in mesh 2 needs to be inversely mapped. This certainly minimizes the number of elements, to which the inverse mapping is applied. In this regard, the present algorithm is very effective and efficient. (2) Analytical solutions to the local co ordinates of any point in a four-node quadrilateral element, which are derived in a rigorous mathematical manner in the context of this paper, make it possible to carry out an inverse mapping process very effectively and efficiently. (3) The use of consistent interpolation enables the interpolated solution to be compatible with an original solution and, therefore guarantees the interpolated solution of extremely high accuracy. After the mathematical formulations of the algorithm are presented, the algorithm is tested and validated through a challenging problem. The related results from the test problem have demonstrated the generality, accuracy, effectiveness, efficiency and robustness of the proposed consistent point-searching algorithm. Copyright (C) 1999 John Wiley & Sons, Ltd. 2007-08-13T00:00:00Z Zhao, CB og Hobbs, BE og Muhlhaus, HB og Ord, A http://espace.library.uq.edu.au/view/UQ:57706 A continuum model for regular block structures is derived by replacing the difference quotients of the discrete equations by corresponding differential quotients. The homogenization procedure leads to an anisotropic Cosserat Continuum. For elastic block interactions the dispersion relations of the discrete and the continuous models are derived and compared. Yield criteria for block tilting and sliding are formulated. An extension of the theory for large deformation is proposed. (C) 1997 by John Wiley & Sons, Ltd. 2007-08-13T00:00:00Z Sulem, J og Muhlhaus, HB http://espace.library.uq.edu.au/view/UQ:220537 2010-11-16T00:00:00Z http://espace.library.uq.edu.au/view/UQ:204723 2010-05-04T00:00:00Z Yu, W og Xing, H. L. http://espace.library.uq.edu.au/view/UQ:103214 2007-08-23T00:00:00Z Xing, H. og Mora, P. R. http://espace.library.uq.edu.au/view/UQ:225128 A discrete element method (DEM) is developed to simulate the heat transfer in granular assemblies in vacuum with consideration of the thermal resistance of rough contact surfaces. Average heat flux is formulated by the positions and heat flow rates of particles on the boundaries of the granular assemblies. Average temperature gradient is given as a best-fit formulation, which is computed from the relative position and temperature of particles. With the thermal boundary condition imposed on the border region, the effective thermal conductivity (ETC) of granular assemblies can be calculated from the average heat flux and temperature gradient obtained from DEM simulations. Moreover, the effects of particle size, solid volume fraction and coordination number on the ETC are also investigated. Simulation results show that granular assemblies with coarse particles and under large external compression forces exhibit a better heat conduction behavior. The effects of particle size and external compression forces on the ETC are in good agreement with experiment observations. © 2010. 2010-12-19T00:00:00Z Zhang, H. W. og Zhou, Q. og Xing, H. L. og Muhlhaus, H. http://espace.library.uq.edu.au/view/UQ:103209 2007-08-23T00:00:00Z Mora, P. R. og Saez, E. og Weatherley, D. K. og Gross, L. og Wang, C. M. http://espace.library.uq.edu.au/view/UQ:38323 A model for finely layered visco-elastic rock proposed by us in previous papers is revisited and generalized to include couple stresses. We begin with an outline of the governing equations for the standard continuum case and apply a computational simulation scheme suitable for problems involving very large deformations. We then consider buckling instabilities in a finite, rectangular domain. Embedded within this domain, parallel to the longer dimension we consider a stiff, layered beam under compression. We analyse folding up to 40% shortening. The standard continuum solution becomes unstable for extreme values of the shear/normal viscosity ratio. The instability is a consequence of the neglect of the bending stiffness/viscosity in the standard continuum model. We suggest considering these effects within the framework of a couple stress theory. Couple stress theories involve second order spatial derivatives of the velocities/displacements in the virtual work principle. To avoid C-1 continuity in the finite element formulation we introduce the spin of the cross sections of the individual layers as an independent variable and enforce equality to the spin of the unit normal vector to the layers (-the director of the layer system-) by means of a penalty method. We illustrate the convergence of the penalty method by means of numerical solutions of simple shears of an infinite layer for increasing values of the penalty parameter. For the shear problem we present solutions assuming that the internal layering is oriented orthogonal to the surfaces of the shear layer initially. For high values of the ratio of the normal-to the shear viscosity the deformation concentrates in thin bands around to the layer surfaces. The effect of couple stresses on the evolution of folds in layered structures is also investigated. (C) 2002 Elsevier Science Ltd. All rights reserved. 2007-08-13T00:00:00Z Muhlhaus, HB og Dufour, F og Moresi, L og Hobbs, B http://espace.library.uq.edu.au/view/UQ:39499 Simulations provide a powerful means to help gain the understanding of crustal fault system physics required to progress towards the goal of earthquake forecasting. Cellular Automata are efficient enough to probe system dynamics but their simplifications render interpretations questionable. In contrast, sophisticated elasto-dynamic models yield more convincing results but are too computationally demanding to explore phase space. To help bridge this gap, we develop a simple 2D elastodynamic model of parallel fault systems. The model is discretised onto a triangular lattice and faults are specified as split nodes along horizontal rows in the lattice. A simple numerical approach is presented for calculating the forces at medium and split nodes such that general nonlinear frictional constitutive relations can be modeled along faults. Single and multi-fault simulation examples are presented using a nonlinear frictional relation that is slip and slip-rate dependent in order to illustrate the model. 2007-08-13T13:44:47Z Mora, P. R. og Weatherley, D. K. http://espace.library.uq.edu.au/view/UQ:204402 2010-04-26T00:00:00Z Liu, E. og Xing, Huilin http://espace.library.uq.edu.au/view/UQ:204396 2010-04-26T00:00:00Z http://espace.library.uq.edu.au/view/UQ:150860 2008-06-06T00:00:00Z Mora, P. R. og Place, D. G. og Jaume, S. C. og Abe, S. http://espace.library.uq.edu.au/view/UQ:96782 2007-08-24T00:00:00Z Mora, P. R. og Place, D. G. http://espace.library.uq.edu.au/view/UQ:101595 2007-08-23T00:00:00Z Saez, E. og Mora, P. R. og Gross, L. og Weatherley, D. K. http://espace.library.uq.edu.au/view/UQ:129784 Tidal deformation of the Earth is normally calculated using the analytical solution with some simplified assumptions, such as the Earth is a perfect sphere of continuous media. This paper proposes an alternative way, in which the Earth crust is discontinuous along its boundaries, to calculate the tidal deformation using a finite element method. An in-house finite element code is firstly introduced in brief and then extended here to calculate the tidal deformation. The tidal deformation of the Earth due to the Moon was calculated for an geophysical earth model with the discontinuous outer layer and compared with the continuous case. The preliminary results indicate that the discontinuity could have different effects on the tidal deformation in the local zone around the fault, but almost no effects on both the locations far from the fault and the global deformation amplitude of the Earth. The localized deformation amplitude seems to depend much on the relative orientation between the fault strike direction and the loading direction (i.e. the location of the Moon) and the physical property of the fault. 2008-02-18T00:00:00Z Xing, H. L. og Zhang, J. og Yin, C. http://espace.library.uq.edu.au/view/UQ:101686 2007-08-23T00:00:00Z Saez, E. og Mora, P. R. og Gross, L. og Weatherley, D. K. http://espace.library.uq.edu.au/view/UQ:101685 2007-08-23T00:00:00Z Davies, M. og Gerschwitz, J. C. og Gross, L. http://espace.library.uq.edu.au/view/UQ:8538 We review the methods available for large deformation simulations of geomaterials before presenting a Lagrangian integration point finite element method designed specifically to tackle this problem. In our ELLIPSIS code, the problem domain is represented by an Eulerian mesh and an embedded set of Lagrangian integration points or particles. Unknown variables are computed at the mesh nodes and the Lagrangian particles carry history variables during the deformation process. This method is ideally suited to model fluidlike behavior of continuum solids which are frequently encountered in geological contexts. We present benchmark examples taken from the geomechanics area. 2006-03-24T00:00:00Z Moresi, Louis N. og Dufour, Frederic og Muhlhaus, Hans http://espace.library.uq.edu.au/view/UQ:150867 2008-06-06T00:00:00Z Place, D. G. og Mora, P. R. http://espace.library.uq.edu.au/view/UQ:256326 The solution of transport problems is a key component for most numerical simulations in Geosciences, for instance in mineralization, CO2 sequestration and ground water flow. Characteristic features of these transport problems are large jumps in material coefficients, in particular through changes in rock porosity. In the paper we present a general framework for solving a general type of transport problems using an operator splitting approach and algebraic upwinding with flux correction. We will test the proposed framework for a typical problem arising from modelling mineralization in a sedimentary structure. The tests indicate that the backward Euler scheme with flux correction has the potential of providing transport solver for Geoscience applications which is weakly scalable for practical scenarios. 2011-10-17T00:00:00Z Gross, Lutz og Gao, Lin http://espace.library.uq.edu.au/view/UQ:174784 Modelling subduction involves solving the dynamic interaction between a rigid (solid yet deformable) plate and the fluid (easily deformable) mantle. Previous approaches neglected the solid-like behavior of the lithosphere by only considering a purely fluid description. However, over the past 5 years, a more self-consistent description of a mechanically differentiated subducting plate has emerged. The key feature in this mechanical description is incorporation of a strong core which provides small resistance to plate bending at subduction zones while simultaneously providing adequate stretching resistance Such that slab Pull drives forward plate motion. Additionally, the accompanying numerical approaches for simulating large-scale lithospheric deformation processes coupled to the underlying viscous mantle flow, have been become available. Here we put forward three fundamentally different numerical strategies, each of which is capabable of treating the advection of mechanically distinct materials that describe the subducting plate. We demonstrate their robustness by calculating the numerically challenging problem of subduction of a 6000 kin wide slab at high-resolution in three-dimensions, the successfuly achievement of which only a few codes in the world can presently even attempt. In spite of the differences of the approaches, all three codes pass the simple qualitative test of developing an "S-bend" trench curvature previously observed in similar models. While reproducing this emergent feature validates that the lithosphere-mantle interaction has been correctly modelled, this is not a numerical benchmark in the traditional sense where the objective is for all codes to achieve exact agreement on a unique numerical Solution. However, we do provide some quantitative comparisons such as trench and plate kinematics in addition to discussing the strength and weaknesses of the individual approaches. Consequently, we believe these developed algorithms can now be applied to study the parameters involved in the dynamics of subduction and offer a toolbox to be used by the entire geoscience community. (C) 2008 Elsevier B.V. All rights reserved. 2009-04-08T00:00:00Z OzBench, Mark og Regenauer-Lieb, Klaus og Stegman, Dave R. og Morra, Gabriele og Farrington, Rebecca og Hale, Alina og May, David, A. og Freeman, Justin og Bourgouin, Laurent og Muhlhaus, Hans og Moresi, Louis http://espace.library.uq.edu.au/view/UQ:35057 A theoretical analysis is carried out to investigate the pore-fluid pressure gradient and effective vertical-stress gradient distribution in fluid saturated porous rock masses in layered hydrodynamic systems. Three important concepts, namely the critical porosity of a porous medium, the intrinsic Fore-fluid pressure and the intrinsic effective vertical stress of the solid matrix, are presented and discussed. Using some basic scientific principles, we derive analytical solutions and explore the conditions under which either the intrinsic pore-fluid pressure gradient or the intrinsic effective vertical-stress gradient can be maintained at the value of the lithostatic pressure gradient. Even though the intrinsic pore-fluid pressure gradient can be maintained at the value of the lithostatic pressure gradient in a single layer, it is impossible to maintain it at this value in all layers in a layered hydrodynamic system, unless all layers have the same permeability and porosity simultaneously. However, the intrinsic effective vertical-stress gradient of the solid matrix can be maintained at a value close to the lithostatic pressure gradient in all layers in any layered hydrodynamic system within the scope of this study. 2007-08-13T00:00:00Z Zhao, CB og Hobbs, BE og Muhlhaus, HB http://espace.library.uq.edu.au/view/UQ:119832 Dynamic simulations of homogeneous and heterogeneous fault rupture using the finite element method are presented giving rise to both crack-like and pulse-like rupture. We employ various slip-weakening frictional laws to examine their effect on the resulting earthquake rupture speed, size and mode. More complex rupture characteristics were produced with more strongly slip-weakening frictional laws, and the degree of slip-weakening had to be finely tuned to reproduce realistic earthquake rupture characteristics. Rupture propagation on a fault is controlled by the constitutive properties of the fault. A dynamic elasto-plastic constitutive law for the interface friction at the fault is formulated based on the Coulomb failure criterion and applied in a way analogous to non-associated elasto-plasticity. We provide benchmark tests of our method against other reported solutions in the literature. We demonstrate the applicability of our elasto-plastic fault model for modeling dynamic rupture and wave propagation in fault systems, and the rich array of dynamic properties produced by our elasto-plastic finite element fault model. These are governed by a number of model parameters including: the spatial and material heterogeneity of the fault, the fault strength, and not least of all the frictional law employed. Asymmetric bilateral fault rupture was produced for the heterogeneous case, where the degree of heterogeneity influenced the rupture speed in the different propagation directions. 2007-10-24T00:00:00Z Olsen-Kettle, Louise og Weatherley, Dion og Saez, Estelle og Gross, Lutz og Muhlhaus, Hans og Xing, Huilin http://espace.library.uq.edu.au/view/UQ:174782 Dynamic simulations of homogeneous, heterogeneous and bimaterial fault rupture using modified slip-weakening frictional laws with static restrengthening are presented giving rise to both crack-like and pulse-like rupture. We demonstrate that pulse-like rupture is possible by making a modification of classical slip-weakening friction to include static restrengthening. We employ various slip-weakening frictional laws to examine their effect on the resulting earthquake rupture speed, size and mode. More complex rupture characteristics were produced with more strongly slip-weakening frictional laws, and the degree of lip-weakening had to be finely tuned to reproduce realistic earthquake rupture characteristics. Rupture propagation on a fault is controlled by the constitutive properties of the fault. We provide benchmark tests of our method against other reported solutions in the literature. We demonstrate the applicability of our elastoplastic fault model for modeling dynamic rupture and wave propagation in fault systems, and the rich array of dynamic properties produced by our elastoplastic finite element fault model. These are governed by a number of model parameters including: the spatial heterogeneity and material contrast across the fault, the fault strength, and not least of all the frictional law employed. Asymmetric bilateral fault rupture was produced for the bimaterial case, where the degree of material contrast influenced the rupture speed in the different propagation directions. 2009-04-08T20:12:28Z Olsen-Kettle, L. M. og Weatherley, D. og Saez, E. og Gross, L. og Muhlhaus, H. B. og Xing, H. L. http://espace.library.uq.edu.au/view/UQ:38712 We conduct a theoretical analysis of steady-state heat transfer problems through mid-crustal vertical cracks with upward throughflow in hydrothermal systems. In particular, we derive analytical solutions for both the far field and near field of the system. In order to investigate the contribution of the forced advection to the total temperature of the system, two concepts, namely the critical Peclet number and the critical permeability of the system, have been presented and discussed in this paper. The analytical solution for the far field of the system indicates that if the pore-fluid pressure gradient in the crust is lithostatic, the critical permeability of the system can be used to determine whether or not the contribution of the forced advection to the total temperature of the system is negligible. Otherwise, the critical Peclet number should be used. For a crust of moderate thickness, the critical permeability is of the order of magnitude of 10(-20) m(2), under which heat conduction is the overwhelming mechanism to transfer heat energy, even though the pore-fluid pressure gradient in the crust is lithostatic. Furthermore, the lower bound analytical solution for the near field of the system demonstrates that the permeable vertical cracks in the middle crust can efficiently transfer heat energy from the lower crust to the upper crust of the Earth. Copyright (C) 2002 John Wiley Sons, Ltd. 2007-08-13T00:00:00Z Zhao, CB og Hobbs, BE og Muhlhaus, HB og Ord, A og Lin, G http://espace.library.uq.edu.au/view/UQ:139060 2008-06-02T17:20:57Z Xu, H. og Xing, H. og Wyborn, D. og Mora, P. R. http://espace.library.uq.edu.au/view/UQ:124055 Exact analytical solutions have been derived rigorously for the pore-fluid velocity, pore-fluid-flow focusing factor, stream function and excess pore-fluid pressure around and within a buried inclined elliptic inclusion in pore-fluid-saturated porous rocks. The geometric characteristics of the buried inclined elliptic inclusion are represented by the aspect ratio and dip angle of the inclusion, while the hydrodynamic characteristic is represented by the permeability ratio of the elliptic inclusion to its surrounding rock. Since an elliptic inclusion of any aspect ratio can be used to approximately represent geological faults and cracks, the present analytical solutions can be used to investigate the pore-fluid-flow patterns around buried faults and cracks within the crust of the Earth. Therefore, the present analytical solution not only provides a better understanding of the physics behind the pore-fluid-flow focusing problem around and within buried faults and cracks, but also provides a valuable benchmark solution for validating any numerical method in dealing with this kind of pore-fluid-flow focusing problem. The pore-fluid-flow focusing factor of a buried elliptic inclusion is demonstrated to be dependent on the aspect ratio, the permeability ratio and the dip angle. 2008-01-25T00:00:00Z Zhao, Chongbin og Hobbs, B. E og Ord, A. og Peng, Shenglin og Liu, Liangming og Muhlhaus, H. B. http://espace.library.uq.edu.au/view/UQ:95352 2007-08-23T00:00:00Z Fielding, C. R. og Trueman, J. og Dickens, G. R. og Page, M http://espace.library.uq.edu.au/view/UQ:95221 2007-08-23T00:00:00Z Fielding, C. R. og Trueman, J. og Dickens, G. R. og Page, M. http://espace.library.uq.edu.au/view/UQ:39472 An equivalent algorithm is proposed to simulate thermal effects of the magma intrusion in geological systems, which are composed of porous rocks. Based on the physical and mathematical equivalence, the original magma solidification problem with a moving boundary between the rock and intruded magma is transformed into a new problem without the moving boundary but with a physically equivalent heat source. From the analysis of an ideal solidification model, the physically equivalent heat source has been determined in this paper. The major advantage in using the proposed equivalent algorithm is that the fixed finite element mesh with a variable integration time step can be employed to simulate the thermal effect of the intruded magma solidification using the conventional finite element method. The related numerical results have demonstrated the correctness and usefulness of the proposed equivalent algorithm for simulating the thermal effect of the intruded magma solidification in geological systems. (C) 2003 Elsevier B.V. All rights reserved. 2007-08-13T00:00:00Z Zhao, CB og Hobbs, BE og Ord, A og Lin, G og Muhlhaus, HB http://espace.library.uq.edu.au/view/UQ:174778 In this paper we propose a new algorithm to simulate the dynamics of 3-D interacting rigid bodies. Six degrees of freedom are introduced to describe a single 3-D body or particle, and six relative motions and interactions are permitted between bonded bodies. We develop a new decomposition technique for 3-D rotation and pay particular attention to the fact that an arbitrary relative rotation between two coordinate systems or two rigid bodies can not be decomposed into three mutually independent rotations around three orthogonal axes. However, it can be decomposed into two rotations, one pure axial rotation around the line between the centers of two bodies, and another rotation on a specified plane controlled by another parameter. These two rotations, corresponding to the relative axial twisting and bending in our model, are sequence-independent. Therefore all interactions due to the relative translational and rotational motions between linked bodies can be uniquely determined using such a two-step decomposition technique. A complete algorithm for one such simulation is presented. Compared with existing methods, this algorithm is physically more reliable and has greater numerical accuracy. 2009-04-08T19:53:43Z Wang, Yucang http://espace.library.uq.edu.au/view/UQ:174781 In this paper we advance the development of our python-based package for the solution of partial differential equations using spatial discretization techniques such as the finite element method (FEM) via two approaches. First we define a Model class object which makes it easy to break down a complex simulation into simpler sub-models, which then can be linked together into a highly efficient whole. Second, we implement an XML schema in which we can save an entire simulation. This allows implemention of check-pointing in addition to graphical user interfaces which enables non-programmers to use models developed for their research. These features are built upon our escript module, a software package designed to develop numerical models in a very abstract way while still allowing the use of computational components implemented in C and C++ to achieve extreme high-performance for time-intensive calculations. 2009-04-08T20:07:30Z Gross, Lutz og Muhlhaus, Hans og Thorne, Elspeth og Steube, Ken http://espace.library.uq.edu.au/view/UQ:197804 2010-03-04T00:00:00Z Tordoir, A. og Weatherley, D. og Onederra, I. og Bye, A. http://espace.library.uq.edu.au/view/UQ:95095 2007-08-23T00:00:00Z Fielding, C. R. og Sliwa, R. og Holcombe, R. J. og Jones, A. T. http://espace.library.uq.edu.au/view/UQ:247057 2011-09-04T00:00:00Z Liu, Yan og Xing, H. L. og Guan, Zhenqun http://espace.library.uq.edu.au/view/UQ:39498 The paper presents a theory for modeling flow in anisotropic, viscous rock. This theory has originally been developed for the simulation of large deformation processes including the folding and kinking of multi-layered visco-elastic rock (Muhlhaus et al. [1,2]). The orientation of slip planes in the context of crystallographic slip is determined by the normal vector - the director - of these surfaces. The model is applied to simulate anisotropic mantle convection. We compare the evolution of flow patterns, Nusselt number and director orientations for isotropic and anisotropic rheologies. In the simulations we utilize two different finite element methodologies: The Lagrangian Integration Point Method Moresi et al [8] and an Eulerian formulation, which we implemented into the finite element based pde solver Fastflo (www.cmis.csiro.au/Fastflo/). The reason for utilizing two different finite element codes was firstly to study the influence of an anisotropic power law rheology which currently is not implemented into the Lagrangian Integration point scheme [8] and secondly to study the numerical performance of Eulerian (Fastflo)- and Lagrangian integration schemes [8]. It turned out that whereas in the Lagrangian method the Nusselt number vs time plot reached only a quasi steady state where the Nusselt number oscillates around a steady state value the Eulerian scheme reaches exact steady states and produces a high degree of alignment (director orientation locally orthogonal to velocity vector almost everywhere in the computational domain). In the simulations emergent anisotropy was strongest in terms of modulus contrast in the up and down-welling plumes. Mechanisms for anisotropic material behavior in the mantle dynamics context are discussed by Christensen [3]. The dominant mineral phases in the mantle generally do not exhibit strong elastic anisotropy but they still may be oriented by the convective flow. Thus viscous anisotropy (the main focus of this paper) may or may not correlate with elastic or seismic anisotropy. 2007-08-13T00:00:00Z Muhlhaus, H. B. og Cada, M. og Moresi, L.