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  • Journal article
    Garcia X, Latham J-P, Xiang J, Harrison JPet al., 2009,

    A clustered overlapping sphere algorithm to represent real particles in discrete element modelling

    , Geotechnique
  • Journal article
    Guises R, Xiang J, Munjiza A, Latham J-Pet al., 2009,

    Granular packing: Numerical Simulation and Characterization of the Effect of Particle Shape

    , Granular Matter, Vol: 11, Pages: 281-292

    The packing of granular particles is investigated using a combined finite-discrete element approach. One of the aims of this paper is to present an application of a recently improved numerical simulation technique for deformable granular material with arbitrary shapes. Our study is focused on the influence of the effect of the particle shape on (1) the emergent properties of a granular pack (packing density,coordination number, force distribution), and on (2) the spatial distribution of the stress.Aset of simulations that mimick the sedimentation process is carried out, with varying input parameters, such as contact friction and particle shape. It is shown that the eccentricity of the particles not only significantly influences the final density of the pack but also the distribution of the stress and the contact forces. The presence of surface friction increases the amount of disorder within the granular system. Stress heterogeneities and force chain patterns propagate through the particles more efficiently than for the frictionless systems. The results also suggest that for the monodisperse systems investigated the coordination number is one of the factors that controls the distribution of the stress within a granular medium.
  • Conference paper
    Latham JP, Mindel J, Guises R, Garcia X, Xiang J, Pain C, Munjiza Aet al., 2009,

    Coupled FEM-DEM and CFD for coastal structures: application to armour stability and breakage

    , Proceedings of the Fifth International Conference on Coastal Structures, Publisher: World Scientific Publishing Co. Pte. Ltd, Pages: 1453-1464
  • Journal article
    Xiang J, McGlinchey D, Latham J-P, 2009,

    An investigation of segregation and mixing in dense phase pneumatic conveying

    , Granular Matter
  • Journal article
    Cotter CJ, Ham DA, Pain CC, Reich Set al., 2009,

    LBB stability of a mixed Galerkin finite element pair for fluid flow simulations

    , Journal of Computational Physics, Vol: 228, Pages: 336-348

    We introduce a new mixed finite element for solving the 2- and 3-dimensional wave equations and equations of incompressible flow. The element, which we refer to as P1D–P2, uses discontinuous piecewise linear functions for velocity and continuous piecewise quadratic functions for pressure. The aim of introducing the mixed formulation is to produce a new flexible element choice for triangular and tetrahedral meshes which satisfies the LBB stability condition and hence has no spurious zero-energy modes. The advantage of this particular element choice is that the mass matrix for velocity is block diagonal so it can be trivially inverted; it also allows the order of the pressure to be increased to quadratic whilst maintaining LBB stability which has benefits in geophysical applications with Coriolis forces. We give a normal mode analysis of the semi-discrete wave equation in one dimension which shows that the element pair is stable, and demonstrate that the element is stable with numerical integrations of the wave equation in two dimensions, an analysis of the resultant discrete Laplace operator in two and three dimensions on various meshes which shows that the element pair does not have any spurious modes. We provide convergence tests for the element pair which confirm that the element is stable since the convergence rate of the numerical solution is quadratic.
  • Journal article
    Xiang J, Munjiza A, Latham JP, Guises Ret al., 2009,

    On the validation of DEM and FEM/DEM models in 2D and 3D

    , Engineering Computations, Vol: 26, Pages: 673-687, ISSN: 0264-4401
  • Journal article
    Latham J-P, Mindel JE, Xiang J, Guises R, Garcia X, Pain CC, Gorman G, Piggott M, Munjiza Aet al., 2009,

    Coupled FEMDEM/Fluids for coastal engineers with special reference to armour stability and breakage

    , Geomechanics and Geoengineering, Vol: 4, Pages: 797-805
  • Journal article
    Fang F, Pain CC, Navon IM, Piggott MD, Gorman GJ, Allison PA, Goddard AJHet al., 2009,

    A POD reduced order unstructured mesh ocean modelling method for moderate Reynolds number flows Ocean Modelling

    , Ocean Modelling, Vol: 28, Pages: 127-136
  • Journal article
    Munjiza A, Xiang J, Garcia X, Latham JP, Schiava DAlbano GG, John NWMet al., 2009,

    The Virtual Geoscience Workbench, VGW: Open Source tools for discontinuous systems

    , Particuology, Vol: in press
  • Journal article
    Neethling SJ, 2008,

    Simple approximations for estimating froth recovery

    , INTERNATIONAL JOURNAL OF MINERAL PROCESSING, Vol: 89, Pages: 44-52, ISSN: 0301-7516
  • Journal article
    Neethling SJ, Cilliers JJ, 2008,

    Predicting and correcting grade-recovery curves: Theoretical aspects

    , INTERNATIONAL JOURNAL OF MINERAL PROCESSING, Vol: 89, Pages: 17-22, ISSN: 0301-7516
  • Journal article
    Xie Z, Lin J, Zhou J, 2008,

    A new unconditionally stable explicit scheme for the convection-diffusion equation with Robin boundary conditions

    , International Journal of Computer Mathematics, Vol: 85, Pages: 1833-1847, ISSN: 0020-7160

    An alternating direction explicit (ADE) scheme to solve the unsteady convection-diffusion equation with Robin boundary conditions is presented and discussed in this paper. It was derived based on the local series expansion method and proved unconditionally stable by von Neumann stability analysis. Thereafter, the ADE scheme is compared with the conventional schemes, and a comparison between the amplification factor of all schemes and the exact one shows that the proposed scheme can simulate well both convection- and diffusion-dominated problems. Finally, the proposed method was validated by a numerical experiment which indicates that, for large cell Reynolds numbers, the proposed scheme, which has unconditional stability, is more accurate than implicit schemes and most explicit schemes. It is also shown that the proposed scheme is simple to implement, economical to use, effective for dealing with Robin boundary conditions and easy to apply to multidimensional problems.
  • Journal article
    Pierazzo E, Artemieva N, Asphaug E, Baldwin EC, Cazamias J, Coker R, Collins GS, Crawford DA, Davison T, Elbeshausen D, Holsapple KA, Housen KR, Korycansky DG, Wunnemann Ket al., 2008,

    Validation of numerical codes for impact and explosion cratering: Impacts on strengthless and metal targets

    , METEORITICS & PLANETARY SCIENCE, Vol: 43, Pages: 1917-1938, ISSN: 1086-9379
  • Journal article
    Gorman GJ, Piggott MD, Wells MR, Pain CC, Allison PAet al., 2008,

    A systematic approach to unstructured mesh generation for ocean modelling using GMT and Terreno

    , Computers & Geosciences, Vol: 34, Pages: 1721-1731, ISSN: 0098-3004

    A systematic approach to unstructured mesh generation for ocean modelling is presented. The method optimises unstructured meshes to approximate bathymetry to a user specified accuracy which may be defined as a function of longitude, latitude and bathymetry. GMT (Generic Mapping Tools) is used to perform the initial griding of the bathymetric data. Subsequently, the Terreno meshing package combines automated shoreline approximation, mesh gradation and optimisation methods to generate high-quality bathymetric meshes. The operation of Terreno is based upon clearly defined error measures and this facilitates the automation of unstructured mesh generation while minimising user intervention and the subjectivity that this can introduce.
  • Journal article
    Bray VJ, Collins GS, Morgan JV, Schenk PMet al., 2008,

    The effect of target properties on crater morphology: Comparison of central peak craters on the Moon and Ganymede.

    , Meteoritics and Planetary Science, Vol: 43, Pages: 1979-1992
  • Journal article
    Osinski GR, Grieve RAF, Collins GS, Marion C, Sylvester Pet al., 2008,

    The effect of target lithology on the products of impact melting

    , METEORITICS & PLANETARY SCIENCE, Vol: 43, Pages: 1939-1954, ISSN: 1086-9379
  • Journal article
    Bosence DWJ, Allison PA, 2008,

    Biotic – Sediment Interactions; an introduction

    , Palaeogeography, Palaeoclimatology, Palaeoecology, Vol: 270, Pages: 217-219, ISSN: 0031-0182
  • Journal article
    Allison PA, Hesselbo SP, Brett CE, 2008,

    Methane seeps on an Early Jurassic dysoxic seafloor

    , Palaeogeography, Palaeoclimatology, Palaeoecology, Vol: 270, Pages: 230-238, ISSN: 0031-0182
  • Journal article
    Collins GS, Kenkmann T, Osinski GR, Wunnemann Ket al., 2008,

    Mid-sized complex crater formation in mixed crystalline-sedimentary targets: Insight from modeling and observation

    , METEORITICS & PLANETARY SCIENCE, Vol: 43, Pages: 1955-1977, ISSN: 1086-9379
  • Journal article
    Latham J-P, Munjiza A, Mindel J, Xiang J, Guises R, Garcia X, Pain C, Gorman G, Piggott Met al., 2008,

    Modelling of massive particulates for breakwater engineering using coupled FEMDEM and CFD

    , PARTICUOLOGY, Vol: 6, Pages: 572-583, ISSN: 1674-2001
  • Journal article
    Paul CRC, Allison PA, Brett CE, 2008,

    The occurrence and preservation of ammonites in the Blue Lias Formation (Lower Jurassic) of Devon and Dorset, England and their palaeoecological, sedimentological and diagenetic significance

    , Palaeogeography, Palaeoclimatology, Palaeoecology, Vol: 270, Pages: 258-272, ISSN: 0031-0182
  • Journal article
    Morris G, Pursell MR, Neethling SJ, Cilliers JJet al., 2008,

    The effect of particle hydrophobicity, separation distance and packing patterns on the stability of a thin film

    , JOURNAL OF COLLOID AND INTERFACE SCIENCE, Vol: 327, Pages: 138-144, ISSN: 0021-9797
  • Journal article
    Neethling SJ, Cilliers JJ, 2008,

    Predicting air recovery in flotation cells

    , MINERALS ENGINEERING, Vol: 21, Pages: 937-943, ISSN: 0892-6875
  • Journal article
    Wells MR, Allison PA, Hampson GJ, Piggott MD, Pain CC, Dodman Aet al., 2008,

    Investigating tides in the Early Pennsylvanian Seaway of NW Eurasia using the Imperial College Ocean Model

    , Geological Association of Canada Special Paper, Vol: 48, Pages: 363-387, ISSN: 0072-1042
  • Journal article
    Smith C, Neethling S, Cilliers JJ, 2008,

    Air-rate profile optimisation: From simulation to bank improvement

    , MINERALS ENGINEERING, Vol: 21, Pages: 973-981, ISSN: 0892-6875
  • Software
    Ham D, Farrell P, Gorman G, Maddison Jet al., 2008,

    Spud

    Spud is a generic system for defining, writing and processing options files for scientific computer models.The interfaces to scientific computer models are frequently primitive, under-documented and ad-hoc text files. This makes using and developing the model in question difficult and error-prone.With Spud, the model developer need only write a rules file (schema) which defines the options which the model takes and the relationship between them. The Spud component Diamond then provides an automatically generated graphical user interface which guides the user and validates the user's input against the schema. Diamond writes out an xml options file for use in Spud.The developer then uses libspud to read the options file into the model. Libspud can read any valid options file without further code modifications and makes the options available at any point in the model code at which they are required.Spud further provides the facility for the schema to be self-documenting and Diamond presents this documentation to the model user in a context-sensitive manner.
  • Journal article
    Kramer SC, Stelling GS, 2008,

    A conservative unstructured scheme for rapidly varied flows

    , INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Vol: 58, Pages: 183-212, ISSN: 0271-2091
  • Journal article
    Merton SR, Pain CC, Smedley-Stevenson RP, Buchan AG, Eaton MDet al., 2008,

    Optimal discontinuous finite element methods for the Boltzmann transport equation with arbitrary discretisation in angle

    , ANNALS OF NUCLEAR ENERGY, Vol: 35, Pages: 1741-1759, ISSN: 0306-4549
  • Conference paper
    Percival JR, Cotter CJ, Holm DD, 2008,

    A Euler–Poincaré framework for the multilayer Green–Nagdhi equations

    , Meeting held in Honor of Darryl D Holms on Geometry and Analysis in Physical Systems, Publisher: IOP Publishing, Pages: 344018-344031, ISSN: 1751-8113

    The Green–Nagdhi equations are frequently used as a model of the wave-like behaviour of the free surface of a fluid, or the interface between two homogeneous fluids of differing densities. Here we show that their multilayer extension arises naturally from a framework based on the Euler–Poincaré theory under an ansatz of columnar motion. The framework also extends to the travelling wave solutions of the equations. We present numerical solutions of the travelling wave problem in a number of flow regimes. We find that the free surface and multilayer waves can exhibit intriguing differences compared to the results of single layer or rigid lid models.
  • Journal article
    Lin JG, Xie ZH, Yu D, Zhou JTet al., 2008,

    A three-point explicit compact difference scheme with arbitrary order of accuracy for the two dimensional pollutant diffusion equation

    , Jisuan Lixue Xuebao/Chinese Journal of Computational Mechanics, Vol: 25, Pages: 511-516, ISSN: 1007-4708

    Based on the successive iterative approach in the Taylor series expansion method, a three-point explicit compact formula with arbitrary order of accuracy for the spatial second order derivative is derived in this paper. With the transformation of the temporal derivative to spatial derivative from the original diffusion equation, a three-point explicit compact difference scheme for the diffusion equation is proposed and it can achieve arbitrary order of accuracy in both space and time. From the numerical test, it is found that the proposed compact scheme is not only simple to implement and economical to use, but also is effective to apply to many theoretical and engineering problems.
  • Conference paper
    Davison TM, Collins GS, Ciesla FJ, 2008,

    Numerical modelling of shock heating in porous planetesmial collisions

    , 71st Annual Meeting of the Meteoritical-Society, Publisher: Meteoritical Society, Pages: A36-A36
  • Journal article
    Collins GS, Morgan J, Barton P, Christeson GL, Gulick S, Urrutia J, Warner M, Wunnemann Ket al., 2008,

    Dynamic modeling suggests terrace zone asymmetry in the Chicxulub crater is caused by target heterogeneity

    , EARTH PLANET SC LETT, Vol: 270, Pages: 221-230, ISSN: 0012-821X
  • Journal article
    Buchan AG, Pain CC, Eaton MD, Goddard AJHet al., 2008,

    Linear and quadratic hexahedral wavelets on the sphere for angular discretizations of the Boltzmann transport equation

    , NUCLEAR SCIENCE AND ENGINEERING, Vol: 159, Pages: 127-152, ISSN: 0029-5639
  • Journal article
    Buchan AG, Pain CC, Eaton MD, Smedley-Stevenson RP, Goddard AJHet al., 2008,

    Chebyshev spectral hexahedral wavelets on the sphere for angular discretisations of the Boltzmann transport equation

    , ANNALS OF NUCLEAR ENERGY, Vol: 35, Pages: 1098-1108, ISSN: 0306-4549
  • Journal article
    Wuennemann K, Collins GS, Osinski GR, 2008,

    Numerical modelling of impact melt production in porous rocks

    , EARTH AND PLANETARY SCIENCE LETTERS, Vol: 269, Pages: 529-538, ISSN: 0012-821X
  • Journal article
    Jackson MD, 2008,

    Characterization of multiphase electrokinetic coupling using a bundle of capillary tubes model

    , JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, Vol: 113, ISSN: 2169-9313
  • Journal article
    Collins GS, Artemieva N, Wuennemann K, Bland PA, Reimold WU, Koeberl Cet al., 2008,

    Evidence that Lake Cheko is not an impact crater

    , TERRA NOVA, Vol: 20, Pages: 165-168, ISSN: 0954-4879
  • Journal article
    Piggott MD, Gorman GJ, Pain CC, Allison PA, Candy AS, Martin BT, Wells MRet al., 2008,

    A new computational framework for multi-scale ocean modelling based on adapting unstructured meshes

    , International Journal for Numerical Methods in Fluids, Vol: 56, Pages: 1003-1015
  • Conference paper
    Piggott MD, Gorman GJ, Pain CC, Allison PA, Candy AS, Martin BT, Wells MRet al., 2008,

    A new computational framework for multi-scale ocean modelling based on adapting unstructured meshes

    , 9th ICFD Conference on Numerical Methods for Fluid Dynamics, Pages: 1003-1015

    A new modelling framework is presented for application to a range of three-dimensional (3D) multi-scale oceanographic problems. The approach is based upon a finite element discretization on an unstructured tetrahedral mesh which is optimized to represent highly complex geometries. Throughout a simulation the mesh is dynamically adapted in 3D to optimize the representation of evolving solution structures. The adaptive algorithm makes use of anisotropic measures of solution complexity and a load-balanced parallel mesh optimization algorithm to vary resolution and allow long, thin elements to align with features such as boundary layers. The modelling framework presented is quite different from the majority of ocean models in use today, which are typically based on static-structured grids. Finite element (and volume) methods on unstructured meshes are, however, gaining popularity in the oceanographic community. The model presented here is novel in its use of unstructured meshes and anisotropic adaptivity in 3D, its ability to represent a range of coupled multi-scale solution structures and to simulate non-hydrostatic dynamics. Copyright (C) 2007 John Wiley & Sons, Ltd.
  • Journal article
    Shaw B, Ambraseys NN, England PC, Floyd MA, Gorman GJ, Higham TFG, Jackson JA, Nocquet J-M, Pain CC, Piggott MDet al., 2008,

    Eastern Mediterranean tectonics and tsunami hazard inferred from the AD 365 earthquake

    , Nature Geoscience, Vol: 1, Pages: 268-276
  • Journal article
    Buchan AG, Pain CC, Eaton MD, Smedley-Stevenson RP, Goddard AJHet al., 2008,

    Self-adaptive spherical wavelets for angular discretizations of the Boltzmann transport equation

    , NUCLEAR SCIENCE AND ENGINEERING, Vol: 158, Pages: 244-263, ISSN: 0029-5639

    A new method for applying anisotropic resolution in the angular domain of the Boltzmann transport equation is presented. The method builds on our previous work in which two spherical wavelet bases were developed for representing the direction of neutral particle travel. The method proposed here enables these wavelet bases to vary their angular approximations so that fine resolution may be applied only to the areas of the unit sphere (representing the direction of particle travel) that are important. We develop an error measure that operates in conjunction with the wavelet bases to determine this importance. A procedure by which the angular resolution is gradually refined for steady-state problems is also given.The adaptive wavelets are applied to three test problems that demonstrate the ability of the wavelets to resolve complex fluxes with relatively few functions, and to achieve this a particular emphasis is placed on their ability to approximate particle streaming through ducts with voids. It is shown that the wavelets are capable of applying the appropriate resolution (as dictated by the error measure) to the directional component of the angular flux at all spatial positions. This method therefore offers a new and highly efficient adaptive angular approximation method.
  • Journal article
    Warner M, Stekl I, Umpleby A, 2008,

    Efficientand effective 3D wavefield tomography

    , 70th European Association of Geoscientists and Engineers Conference and Exhibition 2008: Leveraging Technology. Incorporating SPE EUROPEC 2008, Vol: 3, Pages: 1607-1611

    We demonstrate 3D wavefield tomography applied to surface-streamer seismic data and obtain a result which appears to remove the distoring effects of shallow high-velocity channels.
  • Journal article
    Warner M, Stekl I, Umpleby A, 2008,

    3D wavefield tomography: Synthetic and field data examples

    , SEG Technical Program Expanded Abstracts, Vol: 27, Pages: 3330-3334, ISSN: 1052-3812

    Full wavefield tomography has become well established in two dimensions, but its extension into 3D for realistically sized problems is computationally daunting. In this paper, we present one of the first studies to apply 3D wavefield tomography to field data, and demonstrate that the method can solve useful exploration problems that that are not tractable by other methods.
  • Journal article
    Carmine L, Aristodemou E, Pain C, Muggeridge Aet al., 2008,

    Inversion of time-dependent nuclear well-logging data using neural networks

    , Geophysical Prospecting, Vol: 56, Pages: 115-140, ISSN: 0016-8025

    The purpose of this work was to investigate a new and fast inversion methodology for the prediction of subsurface formation properties such as porosity, salinity and oil saturation, using time-dependent nuclear well logging data. Although the ultimate aim is to apply the technique to real-field data, an initial investigation as described in this paper, was first required; this has been carried out using simulation results from the time-dependent radiation transport problem within a borehole. Simulated neutron and gamma-ray fluxes at two sodium iodide (NaI) detectors, one near and one far from a pulsed neutron source emitting at similar to 14 MeV, were used for the investigation. A total of 67 energy groups from the BUGLE96 cross section library together with 567 property combinations were employed for the original flux response generation, achieved by solving numerically the time-dependent Boltzmann radiation transport equation in its even parity form. Material property combinations (scenarios) and their correspondent teaching outputs (flux response at detectors) are used to train the Artificial Neural Networks (ANNs) and test data is used to assess the accuracy of the ANNs. The trained networks are then used to produce a surrogate model of the expensive, in terms of computational time and resources, forward model with which a simple inversion method is applied to calculate material properties from the time evolution of flux responses at the two detectors. The inversion technique uses a fast surrogate model comprising 8026 artificial neural networks, which consist of an input layer with three input units (neurons) for porosity, salinity and oil saturation; and two hidden layers and one output neuron representing the scalar photon or neutron flux prediction at the detector. This is the first time this technique has been applied to invert pulsed neutron logging tool information and the results produced are very promising. The next step in the procedure is to apply th
  • Journal article
    C J Cotter, G Gorman, 2008,

    Diagnostic tools for 3D unstructured oceanographic data

    , Ocean Modelling, Vol: 20, Pages: 170-182
  • Journal article
    Jonoud S, Jackson MD, 2008,

    New criteria for the validity of steady-state upscaling

    , TRANSPORT IN POROUS MEDIA, Vol: 71, Pages: 53-73, ISSN: 0169-3913
  • Conference paper
    Xiang J, Latham JP, Munjiza A, Mindel Jet al., 2008,

    Applications of the combined finite-discrete element method

    , Discrete Element Methods and Numerical Modelling of Discontinuum Mechanics, Pages: 223-231
  • Book
    Bosence DWJ, Allison PA, 2008,

    Biotic sediment interactions: Selected papers from: Organism sediment relations and preservational windows; A tribute to the scientific career of Roland Goldring. Published in Palaeogeography, Palaeoclimatology, Palaeoecology

    , Publisher: Elsevier Science Ltd.
  • Conference paper
    Pavlidis D, Aristodemou E, Gorman GJ, Gomes JLMA, ApSimon Het al., 2008,

    Numerical Simulation of Air Flows in Street Canyons using Mesh-Adaptive LES

    , Trieste, Italy, ERCOFTAC Workshop: Direct and Large-Eddy Simulations 7 (DLES7)
  • Conference paper
    Latham JP, Mindel J, Xiang J, Garcia X, Pain C, Gorman G, Munjiza Aet al., 2008,

    Development of a modelling approach for large granular media used in coastal applications

    , Discrete Element Methods and Numerical Modelling of Discontinuum Mechanics, Pages: 122-130

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