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  • Open Access


    Investigation of Multi Geometric Uncertainties by Different Polynomial Chaos Methodologies Using a Fictitious Domain Solver

    L. Parussini1, V. Pediroda2

    CMES-Computer Modeling in Engineering & Sciences, Vol.23, No.1, pp. 29-52, 2008, DOI:10.3970/cmes.2008.023.029

    Abstract In this paper different Polynomial Chaos methods coupled to Fictitious Domain approach have been applied to one- and two- dimensional elliptic problems with multi uncertain variables in order to compare the accuracy and convergence of the methodologies. Both intrusive and non-intrusive methods have been considered, with particular attention to their employment for quantification of geometric uncertainties. A Fictitious Domain approach with Least-Squares Spectral Element approximation has been employed for the analysis of differential problems with uncertain boundary domains. Its main advantage lies in the fact that only a Cartesian mesh, that represents the enclosure, needs More >

  • Open Access


    Analysis of EDL Effect for Pressure-Driven 3D Developing Micro-Scale Flow

    E. Y. K. Ng1, S. T. Tan2

    CMES-Computer Modeling in Engineering & Sciences, Vol.23, No.1, pp. 13-28, 2008, DOI:10.3970/cmes.2008.023.013

    Abstract Microchannels have been recognized as a very effective chemical separation and heat transfer device. The electrical double layer (EDL) effect in a micro-scale flow is however anticipated to be critical. In this paper, Nernst-Planck model (NPM), is used to predict the ion concentration distribution as it is reported to be a more appropriate model for developing microchannel flow. The governing equations are discretised for developing rectangular microchannel flows in Cartesians coordinate. An additional body force source term that is relating to the electric potential, resulted from the EDL effect is introduced in the conventional z-axis momentum More >

  • Open Access


    A Class of Wavelet-based Flat Shell Elements Using B-spline Wavelet on the Interval and Its applications

    Xiang Jiawei1, Chen Xuefeng2, Yang Lianfa3, He Zhengjia4

    CMES-Computer Modeling in Engineering & Sciences, Vol.23, No.1, pp. 1-12, 2008, DOI:10.3970/cmes.2008.023.001

    Abstract A class of flat shell elements is constructed by using the scaling functions of two-dimensional tensor product B-spline wavelet on the interval (BSWI). Unlike the process of direct wavelets adding in the wavelet Galerkin method, the element displacement field represented by the coefficients of wavelets expansions was transformed from wavelet space into physical space via the constructed two-dimensional transformation matrix. Then, the BSWI flat shell element is constructed by the assembly of BSWI plane elastomechanics and Mindlin plate elements. Because of the good character of BSWI scaling functions, the BSWI flat shell element combine the More >

  • Open Access


    Perfectly matched layer for acoustic waveguide modeling --- benchmark calculations and perturbation analysis

    Ya Yan Lu1, Jianxin Zhu2

    CMES-Computer Modeling in Engineering & Sciences, Vol.22, No.3, pp. 235-248, 2007, DOI:10.3970/cmes.2007.022.235

    Abstract The perfectly matched layer (PML) is a widely used technique for truncating unbounded domains in numerical simulations of wave propagation problems. In this paper, the PML technique is used with a standard one-way model to solve a benchmark problem for underwater acoustics modeling. Accurate solutions are obtained with a PML layer with a thickness of only a quarter of the wavelength. The effect of a PML is analyzed in a perturbation analysis for waveguides. More >

  • Open Access


    Application of the MLPG to Thermo-Piezoelectricity

    J. Sladek1, V. Sladek1, Ch. Zhang2, P. Solek3

    CMES-Computer Modeling in Engineering & Sciences, Vol.22, No.3, pp. 217-234, 2007, DOI:10.3970/cmes.2007.022.217

    Abstract A meshless method based on the local Petrov-Galerkin approach is proposed for the solution of boundary value problems for coupled thermo-electro-mechanical fields. Transient dynamic governing equations are considered here. To eliminate the time-dependence in these equations, the Laplace-transform technique is applied. Material properties of piezoelectric materials are influenced by a thermal field. It is leading to an induced nonhomogeneity and the governing equations are more complicated than in a homogeneous counterpart. Two-dimensional analyzed domain is subdivided into small circular subdomains surrounding nodes randomly spread over the whole domain. A unit step function is used as More >

  • Open Access


    Lattice Boltzmann Method Simulation of Channel Flow with Square Pillars inside by the Field Synergy Principle

    Cha’o-Kuang Chen1, Shing-Cheng Chang1, Szu-Yu Sun1

    CMES-Computer Modeling in Engineering & Sciences, Vol.22, No.3, pp. 203-216, 2007, DOI:10.3970/cmes.2007.022.203

    Abstract In this study, the channel flow is discussed by the LBM simulations. In the cases of channel with obstacles inside, the square pillars play the role of causing interruption within the fluid field, and hence change the direction of fluid flow. The recirculation region is formed behind the obstacles and influences the fluid passed through not only in the velocity field but also in the temperature field. Therefore, heat transfer is enhanced in local region.
    The field synergy principle is applied in the research to demonstrate that the increased interruption within the fluid increases the More >

  • Open Access


    Effect of Interface Modification on the Mechanical Behavior of Carbon Nanotube Reinforced Composites Using Parallel Molecular Dynamics Simulations

    S. Namilae1, U. Ch,ra2, A Srinivasan3, N. Ch,ra4

    CMES-Computer Modeling in Engineering & Sciences, Vol.22, No.3, pp. 189-202, 2007, DOI:10.3970/cmes.2007.022.189

    Abstract Molecular dynamics (MD) simulations play an important predictive role in understanding the behavior of nanoscale systems. In this paper, parallel MD simulations are used to understand the mechanical behavior of interfaces in CNT based composites. We present an algorithm for parallel implementation of MD simulations of carbon nanotube (CNT) based systems using reactive bond order potentials. We then use that algorithm to model the CNT-polymer interfaces with various levels of interaction as (a) described only by long range Van Der Waals interactions (b) chemically bonded with fixed matrix and (c) chemically bonded with matrix explicitly More >

  • Open Access


    A Meshless Local Petrov-Galerkin Method for Magnetic Diffusion in Non-magnetic Conductors

    J.N. Johnson1, J.M. Owen2

    CMES-Computer Modeling in Engineering & Sciences, Vol.22, No.3, pp. 165-188, 2007, DOI:10.3970/cmes.2007.022.165

    Abstract In this paper, we propose a Meshless Local Petrov-Galerkin method for studying the diffusion of a magnetic field within a non-magnetic (μ = μ0) conducting medium with non-homogeneous and anisotropic electrical resistivity. We derive a local weak form for the magnetic diffusion equation and discuss the effects of different trial/test functions and nodal spacings on its solution. We then demonstrate that the method produces convergent results for several relevant one-dimensional test problems for which solutions are known. This method has the potential to be combined with other mesh-free methods such as Smoothed Particle Hydrodynamics (SPH) to More >

  • Open Access


    Boundary Element Analysis of Three-Dimensional Exponentially Graded Isotropic Elastic Solids

    R. Criado1, J.E. Ortiz1, V. Mantič1, L.J. Gray1,2, F. París1

    CMES-Computer Modeling in Engineering & Sciences, Vol.22, No.2, pp. 151-164, 2007, DOI:10.3970/cmes.2007.022.151

    Abstract A numerical implementation of the Somigliana identity in displacements for the solution of 3D elastic problems in exponentially graded isotropic solids is presented. An expression for the fundamental solution in displacements, Ujl, was deduced by Martin et al. (Proc. R. Soc. Lond. A, 458, pp. 1931--1947, 2002). This expression was recently corrected and implemented in a Galerkin indirect 3D BEM code by Criado et al. (Int. J. Numer. Meth. Engng., 2008). Starting from this expression of Ujl, a new expression for the fundamental solution in tractions Tjl has been deduced in the present work. These quite complex expressions of More >

  • Open Access


    Envelope frequency Response Function Analysis of Mechanical Structures with Uncertain Modal Damping Characteristics

    D. Moens1, M. De Munck, D. Vandepitte

    CMES-Computer Modeling in Engineering & Sciences, Vol.22, No.2, pp. 129-150, 2007, DOI:10.3970/cmes.2007.022.129

    Abstract Recently, an interval finite element methodology has been developed to calculate envelope frequency response functions of uncertain structures with interval parameters. The methodology is based on a hybrid interval implementation of the modal superposition principle. This hybrid procedure consists of a preliminary optimization step, followed by an interval arithmetic procedure. The final envelope frequency response functions have been proved to give a very good approximation of the actual response range of the interval problem. Initially, this method was developed for undamped structures. Based on the theoretical principles of this approach, this paper introduces a new… More >

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