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  • Open Access


    Effects of the Rayleigh Number and the Aspect Ratio on 2D Natural Convection Flows

    Alfredo Nicolás1, Blanca Bermúdez2, Elsa Báez3

    CMES-Computer Modeling in Engineering & Sciences, Vol.48, No.1, pp. 83-106, 2009, DOI:10.3970/cmes.2009.048.083

    Abstract Numerical results of natural convection flows in two-dimensional cavities, filled with air, are presented to study the effects on the characteristics of the flows as some parameters vary: the Rayleigh number Ra and the aspect ratio A of the cavity. This kind of thermal flows may be modeled by the unsteady Boussinesq approximation in stream function-vorticity variables. The results are obtained with a simple numerical scheme, previously reported for isothermal/mixed convection flows, based mainly on a fixed point iterative process applied to the non-linear elliptic system that results after time discretization. The evolution of the flows, mainly flows converging to… More >

  • Open Access


    An Aspect of Hall-Petch Effect in Metallograin Structure

    Michihiko Nakagaki1, Shuji Takashima2, Ryosuke Matsumoto1, Noriyuki Miyazaki2

    CMES-Computer Modeling in Engineering & Sciences, Vol.10, No.3, pp. 199-208, 2005, DOI:10.3970/cmes.2005.010.199

    Abstract The present paper focuses on the micromechanical phenomena occurring in the polycrystalline metal materials. Correlations between the material hardening and the plastic lattice dislocation were discussed with the presence of the grain boundary. The characteristic distribution of the plastic strain gradient is numerically recognized, and hence the validity of incorporating the strain gradient term in the constitutive law is demonstrated. Also, the modeling of the inclusion interface sliding and debonding was performed on the equivalent inclusion theory to develop the constitutive law for the composite. The sliding model is considered to be effective to model the superplastic behavior of highly… More >

  • Open Access


    Some Aspects of the Method of Fundamental Solutions for Certain Biharmonic Problems

    Yiorgos-Sokratis Smyrlis1, Andreas Karageorghis1

    CMES-Computer Modeling in Engineering & Sciences, Vol.4, No.5, pp. 535-550, 2003, DOI:10.3970/cmes.2003.004.535

    Abstract In this study, we investigate the application of the Method of Fundamental Solutions for the solution of biharmonic Dirichlet problems on a disk. Modifications of the method for overcoming sources of inaccuracy are suggested. We also propose an efficient algorithm for the solution of the resulting systems which exploits the symmetries of the matrices involved. The techniques described in the paper are applied to standard test problems. More >

  • Open Access


    The Effect of a Rotational Spring on the Global Stability Aspects of the Classical von Mises Model under Step Loading

    D. S. Sophianopoulos1, G. T. Michaltsos2

    CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.1, pp. 15-26, 2001, DOI:10.3970/cmes.2001.002.015

    Abstract The present work deals with the global stability aspects of a simple two-degrees-of-freedom autonomous initially imperfect damped model, under step (conservative) loading. The proposed system is an extension of the classical limit point one firstly introduced by von Mises, with the addition of a linear rotational spring. The effect of its properties (stiffness and damping) are fully assessed and under certain combinations of the parameters involved a third possibility of postbuckling dynamic response is revealed. This is associated with a point attractor response on a stable prebuckling fixed point, although dynamic buckling has already occurred, a finding validating new relevant… More >

  • Open Access


    Adaptive 3D finite elements with high aspect ratio for dendritic growth of a binary alloy including fluid flow induced by shrinkage

    Jacek Narski1,2, Marco Picasso1

    FDMP-Fluid Dynamics & Materials Processing, Vol.3, No.1, pp. 49-64, 2007, DOI:10.3970/fdmp.2007.003.049

    Abstract An adaptive phase field model for the solidification of binary alloys in three space dimensions is presented. The fluid flow in the liquid due to different liquid/solid densities is taken into account. The unknowns are the phase field, the alloy concentration and the velocity/pressure in the liquid. Continuous, piecewise linear finite elements are used for the space discretization, a semi-implicit scheme is used for time discretization. An adaptive method allows the number of degrees of freedom to be reduced, the mesh tetrahedrons having high aspect ratio whenever needed. Numerical results show that our method is effective and allows to perform… More >

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