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  • Open Access

    ARTICLE

    An Alternated Grid Updating Parallel Algorithm for Material Point Method Using OpenMP

    Yantao Zhang1, Xiong Zhang1,2, Yan Liu1

    CMES-Computer Modeling in Engineering & Sciences, Vol.69, No.2, pp. 143-166, 2010, DOI:10.3970/cmes.2010.069.143

    Abstract Material point method(MPM) is a promising method in solving problems involving large deformations, especially explosion and penetration. In MPM, particles can move around the computing domain dynamically, which can result in load imbalance easily. In parallelizing MPM using OpenMP, data races will occur in the stage of grid node updating if we use loop-level parallelism for these loops. Huang et al. proposed a domain decomposition method to overcome data races [Huang, Zhang, Ma and Wang (2008)]. However, significant modifications of the original serial code are required. In this paper, we proposed a new alternated grid updating method to avoid data… More >

  • Open Access

    ARTICLE

    Explicit Solutions of Stresses for a Three-Phase Elliptic Inclusion Problem Subject to a Remote Uniform Load

    Ching Kong Chao1,2, Chin Kun Chen3, Fu Mo Chen4

    CMES-Computer Modeling in Engineering & Sciences, Vol.69, No.2, pp. 119-142, 2010, DOI:10.3970/cmes.2010.069.119

    Abstract A general solution to a three-phase elliptic inclusion problem subjected to a remote uniform load is provided in this paper. Analysis of the present elasticity problem is rather tedious due to the presence of material inhomogeneities and complex geometric configurations. Based on the technique of conformal mapping and the method of analytical continuation in conjunction with the alternating technique, the general expressions of the displacement and stresses in each layer medium are derived explicitly in a series form. The effects of the material combinations and geometric configurations on the interfacial stresses are discussed in detail and shown in graphic form. More >

  • Open Access

    ARTICLE

    MLPG Application of Nanofluid Flow Mixed Convection Heat Transfer in a Wavy Wall Cavity

    A. Arefmanesh1, M. Najafi2, M. Nikfar3

    CMES-Computer Modeling in Engineering & Sciences, Vol.69, No.2, pp. 91-118, 2010, DOI:10.3970/cmes.2010.069.091

    Abstract Procuring a numerical solution through an application of the meshless local Petrov-Galerkin method (MLPG) on the fluid flow and mixed convection in a complex geometry cavity filled with a nanofluid is the scope of the present study. The cavity considered is a square enclosure having a lower temperature sliding lid at the top, a differentially higher temperature wavy wall at the bottom, and two thermally insulated walls on the sides. The nanofluid medium used is a water-based nanofluid, Al2O3-water with various volume fractions of its solid. To carry out the numerical simulations, the developed governing equations are determined in terms… More >

  • Open Access

    ARTICLE

    Aerodynamic Shape Optimization of Airfoils in Unsteady Flow

    Anant Diwakar1, D. N.Srinath1, Sanjay Mittal1

    CMES-Computer Modeling in Engineering & Sciences, Vol.69, No.1, pp. 61-90, 2010, DOI:10.3970/cmes.2010.069.061

    Abstract Aerodynamic shape optimization of airfoils is carried out for two values of Reynolds numbers: 103 and 104, for an angle of attack of 5o. The objective functions used are (a) maximization of lift (b) minimization of drag and (c) minimization of drag to lift ratio. The surface of the airfoil is parametrized by a 4th order non-uniform rational B-Spline (NURBS) curve with 61 control points. Unlike the efforts in the past, the relatively large number of control points used in this study offer a rich design shape with the possibility of local bumps and valleys on the airfoil surface. The… More >

  • Open Access

    ARTICLE

    Numerical Solution of Dual Phase Lag Model of Bioheat Transfer Using the General Boundary Element Method

    Ewa Majchrzak1

    CMES-Computer Modeling in Engineering & Sciences, Vol.69, No.1, pp. 43-60, 2010, DOI:10.3970/cmes.2010.069.043

    Abstract Heat transfer processes proceeding in domain of heating tissue are discussed. The typical model of bioheat transfer bases, as a rule, on the well known Pennes equation, this means the heat diffusion equation with additional terms corresponding to the perfusion and metabolic heat sources. Here, the other approach basing on the dual-phase-lag equation (DPLE) is considered in which two time delays τq, τT (phase lags) appear. The DPL equation contains a second order time derivative and higher order mixed derivative in both time and space. This equation is supplemented by the adequate boundary and initial conditions. To solve the problem… More >

  • Open Access

    ARTICLE

    Calculation of Potential Second Derivatives by Means of a Regularized Indirect Algorithm in the Boundary Element Method

    H.B. Chen1, Masa. Tanaka2

    CMES-Computer Modeling in Engineering & Sciences, Vol.69, No.1, pp. 19-42, 2010, DOI:10.3970/cmes.2010.069.019

    Abstract Highly accurate calculation of derivative values to the field variable is a key issue in numerical analysis of engineering problems. The boundary integral equations (BIEs) of potential second derivatives are of third order singularities and obviously the direct calculation of these high order singular integrals is rather cumbersome. The idea of the present paper is to use an indirect algorithm which is based on the regularized BIE formulations of the potential second derivatives, following the work of the present first author and his coworkers. The regularized formulations, numerical strategies and example tests are given for both potential first and second… More >

  • Open Access

    ARTICLE

    Self-Adaptive Differential Evolution Based on the Concept of Population Diversity Applied to Simultaneous Estimation of Anisotropic Scattering Phase Function, Albedo and Optical Thickness

    F. S. Lobato1, V. Steffen Jr2, A. J. Silva Neto3

    CMES-Computer Modeling in Engineering & Sciences, Vol.69, No.1, pp. 1-18, 2010, DOI:10.3970/cmes.2010.069.001

    Abstract Differential Evolution Algorithm (DE) has shown to be a powerful evolutionary algorithm for global optimization in a variety of real world problems. DE differs from other evolutionary algorithms in the mutation and recombination phases. Unlike some other meta-heuristic techniques such as genetic algorithms and evolutionary strategies, where perturbation occurs in accordance with a random quantity, DE uses weighted differences between solution vectors to perturb the population. Although the efficiency of DE algorithm has been proven in the literature, studies indicate that the efficiency of the DE methods is sensitive to its control parameters (perturbation rate and crossover rate) and there… More >

  • Open Access

    ARTICLE

    Contact between a Tunnel Lining and a Damage-Susceptible Viscoplastic Medium

    Frederic L. Pellet1

    CMES-Computer Modeling in Engineering & Sciences, Vol.52, No.3, pp. 279-296, 2009, DOI:10.3970/cmes.2009.052.279

    Abstract In this study, the contact and interaction between a tunnel lining support and a damage-susceptible viscoplastic medium is investigated. First, back-analysis of the time-dependent behaviour of a drift excavated across a carboniferous rock mass which exhibited large delayed displacements was undertaken. Drift closure was simulated using an elasto-viscoplastic constitutive model that included the strength degradation process. This 3D numerical simulation was performed taking into account both stage construction sequence and rate of excavation advancement. A comparison of the numerical results with the data measured on site allowed for the calibration of the model parameters. Subsequently, the installation of a concrete… More >

  • Open Access

    ARTICLE

    Fragmentation of Ice Sheets during Impact

    A.P.S.Selvadurai1

    CMES-Computer Modeling in Engineering & Sciences, Vol.52, No.3, pp. 259-278, 2009, DOI:10.3970/cmes.2009.052.259

    Abstract The paper deals with a computational approach for modelling the fragmentation of ice sheets during their impact with stationary structures. The modelling takes into consideration the intact continuum behaviour of the ice as a rate-sensitive elastoplastic material. During impact, the ice sheet can undergo fragmentation, which is controlled by a brittle strength criterion based on the current stress state. The fragmentation allows the generation of discrete elements of the ice sheet, the movements of which are governed by the equations of motion. The contact between individual fragments is governed by a Coulomb criterion. The individual fragments can themselves undergo further… More >

  • Open Access

    ARTICLE

    An Approach to Uncertainty Analysis of Rockfall Simulation

    S. Turrin1, M. Hanss1, A.P.S. Selvadurai2

    CMES-Computer Modeling in Engineering & Sciences, Vol.52, No.3, pp. 237-258, 2009, DOI:10.3970/cmes.2009.052.237

    Abstract Despite the continuing advances in rockfall analysis, the mathematical modeling and simulation of rockfall phenomena continues to be significantly influenced by a large amount of aleatory and epistemic uncertainty on significant number of model parameters. This paper focuses on the representation and quantification of epistemic uncertainties in rockfall modeling and simulation by fuzzy numbers. The propagation of the epistemic uncertainties considered is then calculated by the transformation method as a practical implementation of fuzzy arithmetic. Epistemic uncertainties on the material properties, on the boulder geometry and dimensions, on the kinematics of the impact and on the contact response between boulder… More >

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