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  • Open Access


    Uncertainty Analysis for a Particle Model of Granular Chute Flow

    F. Fleissner1, T. Haag2, M. Hanss2, P. Eberhard1

    CMES-Computer Modeling in Engineering & Sciences, Vol.52, No.2, pp. 181-196, 2009, DOI:10.3970/cmes.2009.052.181

    Abstract In alpine regions human settlements and infrastructure are at risk to be hit by landslides or other types of geological flows. This paper presents a new approach that can aid the design of protective constructions. An uncertainty analysis of the flow around a debris barrier is carried out using a chute flow laboratory model of the actual debris flow. A series of discrete element simulations thereby serves to compare and assess two different barrier designs. In this study, the transformation method of fuzzy arithmetic is used to investigate the influence of epistemically uncertain model parameters. It turns out that parameter… More >

  • Open Access


    A New Combined Scheme of Discrete Element Method and Meshless Method for Numerical Simulation of Continuum/Discontinuum Transformation

    Li Shan, Ning Cui, Ming Cheng, Kaixin Liu

    CMES-Computer Modeling in Engineering & Sciences, Vol.83, No.4, pp. 353-384, 2012, DOI:10.3970/cmes.2012.083.353

    Abstract In the present paper, a combined scheme of discrete element method (DEM) and meshless method for numerical simulation of impact problems is proposed. Based on the basic principle of continuum mechanics, an axisymmetric DEM framework is established for modeling the elastoplastic behavior of solid materials. Failure criteria are introduced to model the transformation from a continuum to a discontinuum. The friction force between contact elements is also considered after the failure appears. So our scheme can calculate not only the behavior of continuum and discontinuum, but also the transformation process from a continuum to a discontinuum. In addition, a meshless… More >

  • Open Access


    Strength of Brittle Materials under High Strain Rates in DEM Simulations

    Jorge Daniel Riera1, Letícia Fleck Fadel Miguel2, Ignacio Iturrioz3

    CMES-Computer Modeling in Engineering & Sciences, Vol.82, No.2, pp. 113-136, 2011, DOI:10.32604/cmes.2011.082.113

    Abstract In the truss-like Discrete Element Method (DEM), masses are considered lumped at nodal points and interconnected by means of uni-dimensional elements with arbitrary constitutive relations. In previous studies of the tensile fracture behavior of concrete cubic samples, it was verified that numerical predictions of fracture of non-homogeneous materials using DEM models are feasible and yield results that are consistent with the experimental evidence so far available. Applications that demand the use of large elements, in which extensive cracking within the elements of the model may be expected, require the consideration of the increase with size of the fractured area, in… More >

  • Open Access


    Developing Mechanistic Understanding of Granular Behaviour in Complex Moving Geometry using the Discrete Element Method. Part A: Measurement and Reconstruction of TurbulaMixer Motion using Positron Emission Particle Tracking

    M. Marigo1,2, D. L. Cairns1, M. Davies1, M. Cook3,A. Ingram2,4,5, E. H. Stitt1

    CMES-Computer Modeling in Engineering & Sciences, Vol.59, No.3, pp. 217-238, 2010, DOI:10.3970/cmes.2010.059.217

    Abstract In this work the complex motion of the Turbulamixer has been measured by Multiple-Positron Emission Particle Tracking (Multiple PEPT) in order to set-up a DEM numerical model. Positron emitting radioactive tracers were attached to three of the pivot bearings on the shaft of the mixer to enable the rotation and translation of the mixer chamber to be tracked in the PEPT camera. The measured movement was mathematically reconstructed and imported into DEM in order to apply the same movement to the modelled vessel. The three-dimensional motion of particles in a vessel located in the Turbula mixer was then calculated using… More >

  • Open Access


    Multi-field Coupling of Particulate Systems

    K. Han1, Y. T. Feng1, D. R. J. Owen1

    CMES-Computer Modeling in Engineering & Sciences, Vol.59, No.1, pp. 1-30, 2010, DOI:10.3970/cmes.2010.059.001

    Abstract A computational framework is established for effective modelling of fluid-thermal-particle interactions. The numerical procedures comprise the Discrete Element Method for simulating particle dynamics; the Lattice Boltzmann Method for modelling the mass and velocity field of the fluid flow; and the Discrete Thermal Element Method and the Thermal Lattice Boltzmann Method for solving the temperature field. The coupling of the three fields is realised through hydrodynamic interaction force terms. Selected numerical examples are provided to illustrate the applicability of the proposed approach. More >

  • Open Access


    Size Effects and Mesh Independence in Dynamic Fracture Analysis of Brittle Materials

    Letícia Fleck Fadel Miguel1, Ignacio Iturrioz2, Jorge Daniel Riera3

    CMES-Computer Modeling in Engineering & Sciences, Vol.56, No.1, pp. 1-16, 2010, DOI:10.3970/cmes.2010.056.001

    Abstract Numerical predictions of the failure load of large structures, accounting for size effects, require the adoption of appropriate constitutive relations. These relations depend on the size of the elements and on the correlation lengths of the random fields that describe material properties. The authors proposed earlier expressions for the tensile stress-strain relation of concrete, whose parameters are related to standard properties of the material, such as Young's modulus or specific fracture energy and to size. Simulations conducted for a typical concrete showed that as size increases, the effective stress-strain diagram becomes increasingly linear, with a sudden rupture, while at the… More >

  • Open Access


    Simulation of the Slow Drag of a Cylinder through a Confined Pressurized Bed of Dumbbell and Elliptically Cylindrical Granules Using the Discrete Element Method

    Fuping Zhou1, Suresh G. Advani2, Eric D. Wetzel3

    CMES-Computer Modeling in Engineering & Sciences, Vol.39, No.1, pp. 49-66, 2009, DOI:10.3970/cmes.2009.039.049

    Abstract Slow drag of a cylinder through a confined, pressurized bed of granules is studied using two-dimensional discrete element method (DEM) simulations. The time-dependent total drag force experienced by the circular cylinder is calculated from the normal and tangential contact forces between the surfaces. To evaluate the role of the granule shape and the aspect ratio on the drag force, the simulation is performed for cylindrical granules, dumbbell-shaped granules, and elliptical granules of three different aspect ratios. Simulation results show that the drag in dumbbell-shaped granules is higher than that in cylindrical granules. In contrast, the drag in elliptical granules decreases… More >

  • Open Access


    Property Predictions for Packed Columns Using Monte Carlo and Discrete Element Digital Packing Algorithms

    C. Xu1, X. Jia2, R. A. Williams2, E. H. Stitt3, M. Nijemeisland3, S. El-Bachir4, A. J. Sederman4, L. F. Gladden4

    CMES-Computer Modeling in Engineering & Sciences, Vol.23, No.2, pp. 117-126, 2008, DOI:10.3970/cmes.2008.023.117

    Abstract Existing theories and computer models for packed columns are either incapable of handling complex pellet shapes or based on over-simplified packing geometry. A digital packing algorithm, namely DigiPac, has recently been developed to fill the gap. It is capable of packing of particles of any shapes and sizes in a container of arbitrary geometry, and is a first step towards a practical computational tool for reliable predictions of packed column properties based on the actual pellet shapes. DigiPac can operate in two modes: a Monte Carlo mode in which particles undergo directional diffusive motions; and a Discrete Element mode where… More >

  • Open Access


    Numerical Simulations of Irregular Particle Transport in Turbulent Flows Using Coupled LBM-DEM

    K. Han 1, Y. T. Feng 1, D. R. J. Owen1

    CMES-Computer Modeling in Engineering & Sciences, Vol.18, No.2, pp. 87-100, 2007, DOI:10.3970/cmes.2007.018.087

    Abstract Numerical procedures are introduced for simulations of irregular particle transport in turbulent flows using the coupled lattice Boltzmann method (LBM) and the discrete element method (DEM). The fluid field is solved by the extended LBM with the incorporation of the Smagorinsky turbulence approach, while particle interaction is modeled by the DEM. The hydrodynamic interactions between fluid and particles are realised through an immersed boundary condition, which gives rise to a coupled solution strategy to model the fluid-particle system under consideration. Main computational aspects comprise the lattice Boltzmann formulation for the solution of fluid flows; the incorporation of the large eddy… More >

  • Open Access


    Modelling of Woven Fabrics with the Discrete Element Method

    D. Ballhause1, M. König1, B. Kröplin1

    CMC-Computers, Materials & Continua, Vol.4, No.1, pp. 21-30, 2006, DOI:10.3970/cmc.2006.004.021

    Abstract The mechanical behaviour of woven fabrics is dominated by the kinematics of the constituents on the microscopic scale. Their macroscopic response usually shows non-linearities which are due to the mobility of the interlaced yarns. The major deformation mechanisms of fabrics, i.e. the crimp interchange in case of biaxial tension and the trellising motion of the yarns in case of shear, reflect the dependency of the macroscopic material behaviour on the microstructural deformation mechanisms.
    We present a novel modelling approach for woven fabrics which is capable to represent directly and locally the microstructure and its kinematics at yarn level. With… More >

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